Just a couple years ago, users had to find somewhere to host their media separately, and then copy and paste the URL into their note whenever they wanted to share their cat pictures. One of the first, if not the first, media hosting services specifically intended for Nostr was nostr.build, which will be the service we are reviewing today.

Like our previous review of Amber, Nostr.Build is a service for users to pair with other Nostr apps. You won't generally use nostr.build by itself. Rather, you'll use it to host that incredible shot you want to post to #Olas, or to host screenshots for your long-form tutorial about setting up Nostr Wallet Connect that you'll be posting from #Habla.news, or for hosting a hilarious video of your cat falling asleep to walker's voice and taking a tumble off of his favorite perch that you want to share on #Damus. However, there are some features within Nostr.Build that you may want to check out quite apart from using it with any other Nostr app.

Overall Impression

Score: 4.8 / 5

I have been impressed by Nostr.Build for some time now, but they have pulled out all the stops in their latest update, increasing their maximum file size for free accounts to 100MB, integrating the #Blossom protocol, adding the ability to share directly to Nostr from within your dashboard, and more integrations with other Nostr apps than ever before. Nostr.Build is simply a pleasure to use, whether through their web interface, or through another Nostr app that integrates with them.

With the ability to easily organize your media, view statistics, browse the media gallery of free uploads, metadata removal for increased privacy, and AI image generation, Nostr.Build is not simply a media hosting service, it is a full-fledged media management platform. Its robust features keep it well ahead of other Nostr-focused media hosting options available, and a particularly strong option for those using Blossom and wanting redundancy and reliable uptime for their media.

As much as I enjoy using the web interface, though, where Nostr.Build really shines is their integrations with other Nostr apps. These integrations allow users to have the same experience they are accustomed to from centralized social platforms of uploading their media from within the same app they are using to share it. No copy/pasting a URL from one app to another. In fact, many users may not realize they have been using Nostr.Build in their client of choice, simply because it is the default option for media hosting for many Nostr apps.

This has the added benefit to client developers that they can provide this experience to their users without having to run media hosting infrastructure on top of trying to build their app. The separation of relays, clients, and media hosting between different entities, while keeping a similar experience to centralized platforms where a single company controls all three, is critical to Nostr adoption.

Features

Nostr.Build has a plethora of features beyond simply hosting your media. Let's take a look!

AI Image Generation

Do you need a quick title image for a long-form article? How about inspiration for a logo or art piece? Nostr.Build's AI Studio has you covered.

They have provided a few different models based on the plan you purchase, beginning with the Professional plan, which includes SDXL-Lightning and Stable Diffusion 1. Upgrading to the Creator plan will give you access to all Pro Stable Diffusion models and unlimited use of the Flux.1 model, which is the same core model used for Grok2 images.

I personally have a Professional account, so I haven't had a chance to try out Flux.1, but I have used Stable Diffusion extensively for creating character art for #NostrHeroes characters, such as these:

Nothing too spectacular when compared with some of the newer models out there, and there is no image-to-image support (yet), but more than adequate for casual image generation needs. Moreover, it is far more than what one would expect from a simple media-hosting service.

Admittedly, I am also no expert at coaxing AI models to produce anything remarkable so your results may vary. Either way, image generation is a welcome tool to have available without needing to go to an outside service unless you require something very specific.

Upload Limits

The maximum file size limits on Nostr.Build have been getting progressively larger, even for their free service. As I recall, it was a mere 21MB limit per file just a few months ago, which is fine for image files, but is quickly exceeded with videos. Then they increased their limits to 50MB per file, and as of recent updates it has been increased once more to a whopping 100MB per file... for free! This is more than adequate for most uses.

However, free users' images, GIFs, and videos are automatically viewable via Nostr.Build's free media gallery. This is something to particularly bear in mind when uploading images you intend to share via direct message. Though your DMs are encrypted, the images uploaded to Nostr.Build are not, and if you don't have a paid account, they will be viewable to the all paid users in the free media gallery. If you want to upload images that will not be viewable unless you actively share them, you must have a paid account.

Paid accounts have no file size limit, but they do have a total storage limit. I could not find anything about total storage limits for free accounts, but Professional tier will give you 25GB, Creator 50GB, and Advanced 250GB. Uploads to paid accounts are not visible in the free media gallery, so only those you give the link to will be able to access your content.

Media Types

Many file types are supported by Nostr.Built, even for free users, including:

• Image: .jpg, .png, .gif
• Video: .mov, mp4
• Audio: mp3, .wav

Upgrading to the Professional plan will add .pdf and .svg to the list of permitted file types, and upgrading to Creator or above will add .zip files, as well.

I believe other common file types are also supported, but these are the only ones specifically mentioned on the site.

Free Media Gallery

The free media gallery is an interesting little feature that Nostr.Build has available to paid accounts. Free users can get a preview, such as the one below, but only paid users can browse through the millions of uploads made by free users.

Apart from being amusing to browse through the things people have been uploading, I am unsure of how useful this particular feature is. No indication is given as to who uploaded the media, and it is limited compared to media feeds in other Nostr apps in two important ways. First, it only shows media uploaded to Nostr.Build, while other media-focused Nostr apps, such as Slidestr, Lumina, or even Primal will show media posted by all Nostr users. Second, Nostr.Build's gallery doesn't show all uploads to Nostr.Build, but only uploads from those without a paid account, further limiting the scope of whose uploads are seen.

Paid users have the advantage of being able to upload media that is not viewable to anyone unless they intentionally share the link somewhere. Free users, on the other hand, must be aware that their uploads are viewable by any paid users, whether they shared the link anywhere or not.

One incident I had while testing out another app required me to reach out to Nostr.Build support to request deletion of an image. It had some of my personal information in it, and had been uploaded to Nostr.Build and sent to me via DM. The sender assumed that since it was being sent via DM, no one else would be able to see the image, but because he was not a paid user of Nostr.Build, the image was included in the Free Media Gallery for any paid user to see. Not ideal, but the folks at Nostr.Build were quick to get it deleted for me.

In short, I have mixed feelings about this particular feature.

Blossom

Blossom is a media storage and retrieval protocol built for Nostr, but usable with any application that needs to access media via the web, and Nostr.Build has recently added support for Blossom uploads via their Blossom server: blossom.band

I will likely be adding a Nostrversity article going over Blossom in detail in the near future, but here's the basics of what it makes possible:

First, easy integration for media uploading from your favorite Nostr apps. Amethyst, Coracle, Primal and others have added Blossom upload support, so you just have to hop into your settings and add Nostr.Build's Blossom server address to start using it as your media host. No need to go to a separate app to upload your media and copy/paste the URL into your Nostr note!

Second, your media in Blossom is content addressable. This means it is named based on a hash of its actual data. Because of this, you can verify that the media has not been altered or replaced by your media host. If the hash doesn't match the data, it won't be loaded by the Nostr client, so you never have to worry about the image in your note being replaced by a different image by your media host.

Finally, because your media is addressable by its content, you can save the same media to multiple hosts, and if one of them goes down, Nostr apps can fetch your media from other hosts, just like they can do with your notes by fetching them from different relays if one relay you write to is down. This makes your images and videos much harder to censor, since you would need to be banned by multiple Blossom servers for your media to no longer be accessible.

If you would like to upload media to more than one Blossom server at the same time, your options are currently to use Primal and ensure that your settings have "Enable media mirrors" toggled on, or to use Bouquet. Hopefully we will see this option added to more Nostr apps in the near future.

Metadata Stripping

For files uploaded via Nostr.Build's dashboard, location metadata is removed upon upload. This is to protect user privacy, since this data could be used to reveal your home address if it is left attached to images posted publicly on Nostr.

When uploading via Blossom, media containing location metadata will be rejected. The user will be required to remove the metadata before they can upload the media.

No KYC and No Ads Policy

The only form of identification needed to use Nostr.Build is your Nostr identity. Every upload is tied to your npub, but no name, date of birth, email, or other identifying information is required. This is made possible because Nostr.Build only accepts Bitcoin as payment for their accounts, and no KYC is required to make Bitcoin transactions via Lightning.

Additionally, Nostr.Build is philosophically opposed to targeted advertising, so they have a policy that they will never use ads on their hosting service.

Client Integrations

Even before Blossom, Nostr.Build had many Nostr clients that used it as the default media hosting service, allowing users to upload directly within the app. This has only expanded now that Nostr.Build has added Blossom.

A very non-exhaustive list of clients that integrate with Nostr.Build is listed on their site, and includes Damus, Amethyst, Nostrudel, Snort, Iris, Coracle, Flycat, and Yakihonne. Additional apps that support Nostr.Build via Blossom include Primal and Flotilla. Some of these integrations support both Blossom and NIP-96 options for uploading media, such as Amethyst, while others only support one or the other.

I would not be surprised to see more and more Nostr apps move to integrating Blossom and phasing out NIP-96 support. Either way, though, Nostr.Build currently supports both, and is therefore an excellent hosting option if you want to use it with a wide range of Nostr apps.

Media Statistics

For those with a paid account, Nostr.Build provides information about how often each of your uploads has been requested and viewed within a given time period.

This can be valuable information for content creators, so they can determine what content is resonating with their audience, and what times of day their posts get the most views.

This information can currently be viewed for a maximum period of three months prior to the current date, and as short a period as just the past hour.

Can My Grandma Use It?

Score: 4.7 / 5

Nostr.Build is incredibly easy to use if you have a paid account, or if you are a free user uploading to Nostr.Build through a client that integrates with them by default. Previous frictions encountered by free users trying to upload large files should now be few and far between, thanks to the generous 100MB size limit.

Where things may be a bit more involved is when users are trying to set up media hosting on Nostr apps that don't use Nostr.Build by default. Exactly where in the settings the user must go to set this up, and whether to use the Blossom or NIP-96 address may not be immediately apparent, and requires an understanding of the difference that the user may not possess. This is not the fault of Nostr.Built, though, and I have not taken it into consideration in the scoring. Each individual Nostr app's settings should be as easy to understand as possible.

Another point of friction may come from free users who want to upload directly through the Nostr.Build site, instead of via another Nostr app. This used to be possible without logging in, but in an effort to ensure the service was used for Nostr, and not for general media hosting, Nostr.Build added the requirement to log in.

Thankfully, there are plenty of login options, including npub and password, browser extension (NIP-07), and even via a one-time-code sent to you via Nostr DM. However, if you don't have a paid account already, logging in will prompt you to upgrade. It seems that uploading directly via the website has been removed for free users entirely. You can only upload via another Nostr app if you don't have a paid account. This may lead to confusion for users who don't want to pay for an account, since it isn't made apparent anywhere that uploading through the website isn't an option for them.

Additionally, I would like to see the addresses for the Blossom server and for NIP-96 uploads (unless they are being phased out) added to the main page somewhere. Even selecting the "Blossom" page from the site navigation doesn't make clear what needs to be done to utilize the service. Something as simple as, "To use Nostr.Build with your favorite Blossom compatible Nostr apps, just add https://blossom.band as your media host in the app settings," would be enough to point users in the right direction.

For those who do have paid accounts, the dashboard is easy to navigate and organize your media.

By default, all uploads are added to the Main Folder. Users can leave them there, or they can easily create new folders and drag and drop media to organize it.

Every image has a copy/paste clipboard icon for ready access to copy the media URL for inclusion into a Nostr note.

Additionally, Nostr.Build allows users to share their uploaded media to Nostr directly from the dashboard. Bear in mind, though, this is published to a set of popular relays, without taking into account the user's preferred write relays.

The section just below the user's profile information gives an at-a-glance view of important information, such as how much of the user's allotted storage has been used, how many AI Studio credits are available, how many days are left before their paid account must be renewed, and how many files from three major categories — GIFs, images, and videos — have been uploaded.

Uploading directly to the dashboard is also incredibly easy. You can simply drag and drop files into the upload pane, or browse for them. If you have a URL for the media you want to upload, you can even paste it to import from another website or Blossom server.

Anything I could think of that I might want to do in the interface was intuitive to find, well labeled, or had common and easily identified icons.

How do UI look?

Score: 4.7 / 5

I would describe Nostr.Build's UI as clean and utilitarian, which is what one would expect from a media hosting service. Nothing too flashy. Just what you need and nothing you don't.

We certainly like our purple color-schemes on Nostr, and Nostr.Build leans into that with white text on shades of purple backgrounds, along with occasional color-popping accents. If a Nostr client had made the same color choices, I might be a bit more critical, but it works in an app that users won't be spending a ton of time in, except while managing their media, or using the AI Studio to generate some images.

UI elements such as buttons, active folder indicators, and icons all maintain an attractive, and simple design, with rounded corners wherever appropriate. Nothing looks too busy or overbearing, and the spacing between image previews in the folder view is just right.

Font remains consistent throughout the interface, with no jarring changes, and bold text, in white or another contrasting color, is used appropriately to draw attention, while subdued text is rendered in a light purple to blend more with the background, while remaining readable.

As such, the UI is attractive, without being particularly breathtaking. Nothing to complain about, but also nothing to write home about.

Log In Options

Score: 4.8 / 5

As mentioned previously, Nostr.Build provides three ways a user can log in.

The first should be very familiar for any Nostr user who frequents web clients, and that is by use of a browser extension (NIP-07), such as Alby, Nos2x, or Gooti. Note, this will also work if you are on Android and using KeyChat's browser, which has a NIP-07 signer built in.

Next is the legacy login method for Nostr.Build that they have used since the service first launched, which is via npub and password. This should serve to remind you that even though Nostr.Build supports Nostr login, and can post your images to Nostr for you, it's really just a centralized media hosting service. Just like you wouldn't use only one Nostr relay, you should not use just one media host. Mirror your media to other Blossom servers.

Most intriguing, and one I had not seen used before, is the option to use your npub and have a one-time-code sent to you via Nostr DM. I tested this method out and it worked flawlessly. It is unfortunately using the old NIP-04 DM spec, though, so any clients that have deprecated these DMs will not work for receiving the code. We're in a strange place with Nostr DMs currently, with some clients deprecating NIP-04 DMs in favor of NIP-17, others that still only support NIP-04, and a few that support both. If you don't see the DM in your client of choice, hop over to Primal and check your DMs there in the "other" tab.

Since Nostr.Build is supporting Nostr login, I would like to see them add remote signer (NIP-46) login alongside browser extension login to round out the options expected from a Nostr web app.

Feature Set

Score: 4.8 / 5

The features provided by Nostr.Build all work as expected and provide a lot of value to the user. With only one exception, all of the features make sense for a media hosting and management service to provide, and they are adding more features all the time.

Users not only get a reliable hosting service, with excellent uptime for their media, but they get integrations with most Nostr clients I can think of, Blossom protocol support, media organization and statistics, posting media to Nostr from within the dashboard, metadata stripping for enhanced privacy, a wide range of supported file types, and an AI image generation studio! What's more, there are additional features already on the roadmap, including traditional and AI image editing, additional plan options, expandable storage, and video transcoding for optimized playback. Nostr.Build is just getting started and they already offer more than most media hosting services out there, intended for Nostr or otherwise.

The one feature I am still not sold on is the "Free Media Gallery." The name is misleading. The gallery itself is not free. You must have a paid account to access more than a preview of it. Rather, it displays media uploaded by free users, regardless of whether they uploaded that media to send via DM, or uploaded it but decided not to share it out, or uploaded it to post it only within a private group on Flotilla, or uploaded it and only sent the note with the image link to a private relay.

Moreover, if I want to see media that has been shared on Nostr, there are plenty of ways I can do so that I can be confident only include media users intended to be publicly viewable. This feature from Nostr.Build, if it is kept at all, should have some way of ensuring the gallery only includes images that were shared on public relays.

Pricing

Score: 5 / 5

The pricing structure for Nostr.Build is exceptionally reasonable when compared with other services.

The Professional plan, which is their lowest paid tier, is just 69,000 sats a year. At current price, that translates to around $70 for the year, and Nostr.Build has been known to lower their pricing as Bitcoin goes up. Users can also get a 10% or 20% discount if they buy 2 or 3 years at a time, compensating for the fact that Bitcoin tends to go up year over year.

For that cost, users get 25GB of storage, unlimited file size for uploads within that storage cap, and access to all of Nostr.Build's features mentioned in this review, with the exception of their highest end AI models and storage of certain file types.

If I were to set up my own VPS to host a Blossom server with comparable storage, I would be paying around $14 a month before the cost of the domain, and it would be anything but plug and play. Even then, all I would have is storage. I would be missing out on all of the other features Nostr.Build has out of the box for less than half the price.

The Creator plan is close to double the cost at 120,000 sats, or about $120, a year. However, you aren't just getting double the storage space at 50GB; you are also getting double the AI credits, access to the higher tier AI models, S3 backup for all of your media, and your own Creator page you can share out with your media available for others to browse in one location.

The Advanced plan doesn't add a lot of extra features for more than double the price of the Creator plan, but it MASSIVELY increases your storage limit by 5x to a total of 250GB. Comparable storage space on a VPS to run your own Blossom server would be about $100 a month and Nostr.Build is offering it for about $250 (250,000 sats) for a whole year! If you really need to host that much media, it's hard to beat this price. The plan also comes with a Nostr.Build NIP-05 address, if you need one.

Now, the argument can be made, "But it's priced in sats, and that means in four years I will have spent many times that dollar amount on their service, possibly making it more expensive than other services priced in fiat." While that is true, it also doesn't take opportunity cost into account. Every dollar you spend on something other than Bitcoin is a missed opportunity to have bought Bitcoin with it. There's not really any difference between spending $70 in fiat to buy a hosting plan vs spending 69,000 sats, because you could have used that same $70 to buy Bitcoin instead, so you are losing out on that increase in purchasing power either way.

Not to mention, you can just buy the sats with your fiat and send it to Nostr.Build, so you would effectively be buying your plan with fiat, and they would be receiving sats.

I think Satellite.earth is still technically less expensive at just $0.05 per GB per month, which comes to $15 a year for the same 25GB of Nostr.Build's professional plan. However, all you get is media hosting. You miss out on all of the other features provided by Nostr.Build. And if you are uploading files of 100MB or less... Well, free with Nostr.Build is still cheaper than $0.5 per GB.

Wrap Up

All of the above comes together to make Nostr.Build a versatile and full-featured media hosting and management service at an affordable price point for their paid accounts, but with no need to pay at all if you just want a place to upload photos, GIFs, memes, and even some videos, so long as the file size stays under 100MB. Whether you want to use Nostr.Build as your primary media host, or as just one redundancy in your Blossom set up, they have you covered and I encourage you to check them out!

For the next review, I would like to go with another client, this time for the web, and the two options I am debating between are Coracle.social and Jumble.social. Let me know in the comments which you would like to see!

Instead, we will be reviewing a very useful tool created and maintained by greenart7c3 called #Amber. For those unfamiliar with Amber, it is an #Android application dedicated to managing your signing keys, and allowing you to log into various #Nostr applications without having to paste in your private key, better known as your #nsec. It is not recommended to paste your nsec into various applications because they each represent another means by which it could be compromised, and anyone who has your nsec can post as you. On Nostr, your #npub is your identity, and your signature using your private key is considered absolute proof that any given note, reaction, follow update, or profile change was authorized by the rightful owner of that identity.

It happens less often these days, but early on, when the only way to try out a new client was by inputting your nsec, users had their nsec compromised from time to time, or they would suspect that their key may have been compromised. When this occurs, there is no way to recover your account, or set a new private key, deprecating the previous one. The only thing you can do is start over from scratch, letting everyone know that your key has been compromised and to follow you on your new npub.

If you use Amber to log into other Nostr apps, you significantly reduce the likelihood that your private key will be compromised, because only one application has access to it, and all other applications reach out to Amber to sign any events. This isn't quite as secure as storing your private key on a separate device that isn't connected to the internet whatsoever, like many of us have grown accustomed to with securing our #Bitcoin, but then again, an online persona isn't nearly as important to secure for most of us as our entire life savings.

Amber is the first application of its kind for managing your Nostr keys on a mobile device. greenart7c3 didn't merely develop the application, but literally created the specification for accomplishing external signing on Android which can be found in NIP-55. Unfortunately, Amber is only available for Android. A signer application for iOS is in the works from Terry Yiu, but is not ready for use at this time. There is also a new mobile signer app for Android and iOS called Nowser, but I have not yet had a chance to try this app out. From a cursory look at the Android version, it is indeed in the very early stages of development and cannot be compared with Amber.

This review of Amber is current as of version 3.2.5.

Overall Impression

Score: 4.7 / 5 (Updated 4/21/2025)

I cannot speak highly enough about Amber as a tool that every Nostr user on Android should start using if they are not already. When the day comes that we have more options for well-developed signer apps on mobile, my opinion may very well change, but until then Amber is what we have available to us. Even so, it is an incredibly well thought-out and reliable tool for securing your nsec.

Despite being the only well-established Android signer available for Android, Amber can be compared with other external signing methods available on other platforms. Even with more competition in this arena, though, Amber still holds up incredibly well. If you are signing into web applications on a desktop, I still would recommend using a browser extension like #Alby or #Nos2x, as the experience is usually faster, more seamless, and far more web apps support this signing method (NIP-07) than currently support the two methods employed by Amber. Nevertheless that gap is definitely narrowing.

A running list I created of applications that support login and signing with Amber can be found here: Nostr Clients with External Signer Support

I have run into relatively few bugs in my extensive use of Amber for all of my mobile signing needs. Occasionally the application crashes when trying to send it a signing request from a couple of applications, but I would not be surprised if this is no fault of Amber at all, and rather the fault of those specific apps, since it works flawlessly with the vast majority of apps that support either NIP-55 or NIP-46 login.

I also believe that mobile is the ideal platform to use for this type of application. First, because most people use Nostr clients on their phone more than on a desktop. There are, of course, exceptions to that, but in general we spend more time on our phones when interacting online. New users are also more likely to be introduced to Nostr by a friend having them download a Nostr client on their phone than on a PC, and that can be a prime opportunity to introduce the new user to protecting their private key. Finally, I agree with the following assessment from hodlbod.

nostr:nevent1qqsw0r6gzn05xg67h5q2xkplwsuzedjxw9lf7ntrxjl8ajm350fcyugprfmhxue69uhhyetvv9ujumn0wd68yurvv438xtnrdaksyg9hyaxj3clfswlhyrd5kjsj5v04clhjvgeq6pwztmysfzdvn93gev7awu9v

The one downside to Amber is that it will be quite foreign for new users. That is partially unavoidable with Nostr, since folks are not accustomed to public/private key cryptography in general, let alone using a private key to log into websites or social media apps. However, the initial signup process is a bit cumbersome if Amber is being used as the means of initially generating a key pair. I think some of this could be foregone at start-up in favor of streamlining onboarding, and then encourage the user to back-up their private key at a later time.

Features

Amber has some features that may surprise you, outside of just storing your private key and signing requests from your favorite Nostr clients. It is a full key management application, supporting multiple accounts, various backup methods, and even the ability to authorize other users to access a Nostr profile you control.

Android Signing

This is the signing method where Amber really shines in both speed and ease of use. Any Android application that supports this standard, and even some progressive web-apps that can be installed to your Android's home-screen, can very quickly and seamlessly connect with Amber to authorize anything that you need signed with your nsec. All you have to do is select "Login with Amber" in clients like #Amethyst or #0xChat and the app will reach out to Amber for all signing requests from there on out. If you had previously signed into the app with your nsec, you will first need to log out, then choose the option to use Amber when you log back in.

This is a massive deal, because everything you do on Nostr requires a signature from your private key. Log in? Needs a signature. Post a "GM" note? Needs a signature. Follow someone who zapped your note? Needs a signature. Zap them back? You guessed it; needs a signature. When you paste your private key into an application, it will automatically sign a lot of these actions without you ever being asked for approval, but you will quickly realize just how many things the client is doing on your behalf when Amber is asking you to approve them each time.

Now, this can also get quite annoying after a while. I recommend using the setting that allows Amber to automatically sign for basic functions, which will cut down on some of the authorization spam. Once you have been asked to authorize the same type of action a few times, you can also toggle the option to automatically authorize that action in the future. Don't worry, though, you have full control to require Amber to ask you for permission again if you want to be alerted each time, and this toggle is specific to each application, so it's not a blanket approval for all Nostr clients you connect with.

This method of signing is just as fast as signing via browser extension on web clients, which users may be more accustomed to. Everything is happening locally on the device, so it can be very snappy and secure.

Nostr Connect/Bunker Signing

This next method of signing has a bit of a delay, because it is using a Nostr relay to send encrypted information back and forth between the app the user is interacting with and Amber to obtain signatures remotely. It isn't a significant delay most of the time, but it is just enough to be noticeable.

Also, unlike the previous signing method that would automatically switch to Amber as the active application when a signing request is sent, this method only sends you a notification that you must be watching for. This can lead to situations where you are wondering why something isn't working in a client you signed into remotely, because it is waiting on you to authorize the action and you didn't notice the notification from Amber. As you use the application, you get used to the need to check for such authorization requests from time to time, or when something isn't working as expected.

By default, Amber will use relay.nsec.app to communicate with whichever Nostr app you are connecting to. You can set a different relay for this purpose, if you like, though not just any relay will support the event kinds that Amber uses for remote signing. You can even run your own relay just for your own signing purposes. In fact, the creator of Amber has a relay application you can run on your phone, called Citrine, that can be used for signing with any web app you are using locally on your phone. This is definitely more of an advanced option, but it is there for you if you want it. For most users, sticking with relay.nsec.app will be just fine, especially since the contents of the events sent back and forth for signing are all encrypted.

Something many users may not realize is that this remote signing feature allows for issuing signing permissions to team members. For instance, if anyone ever joined me in writing reviews, I could issue them a connection string from Amber, and limit their permissions to just posting long-form draft events. Anything else they tried to do would require my explicit approval each time. Moreover, I could revoke those permissions if I ever felt they were being abused, without the need to start over with a whole new npub. Of course, this requires that your phone is online whenever a team member is trying to sign using the connection string you issued, and it requires you pay attention to your notifications so you can approve or reject requests you have not set to auto-approve. However, this is probably only useful for small teams, and larger businesses will want to find a more robust solution for managing access to their npub, such as Keycast from JeffG .

The method for establishing a connection between Amber and a Nostr app for remote signing can vary for each app. Most, at minimum, will support obtaining a connection string from Amber that starts with "bunker://" and pasting it in at the time of login. Then you just need to approve the connection request from Amber and the client will log you in and send any subsequent signing requests to Amber using the same connection string.

Some clients will also offer the option to scan a QR code to connect the client to Amber. This is quite convenient, but just remember that this also means the client is setting which relay will be used for communication between the two. Clients with this option will also have a connection string you can copy and paste into Amber to achieve the same purpose. For instance, you may need this option if you are trying to connect to an app on your phone and therefore can't scan the QR code using Amber on the same phone.

Multiple Accounts

Amber does not lock you into using it with only a single set of keys. You can add all of your Nostr "accounts" to Amber and use it for signing events for each independently. Of course, Nostr doesn't actually have "accounts" in the traditional sense. Your identity is simply your key-pair, and Amber stores and accesses each private key as needed.

When first signing in using native Android signing as described above, Amber will default to whichever account was most recently selected, but you can switch to the account that is needed before approving the request. After initial login, Amber will automatically detect the account that the signing request is for.

Key Backup & Restore

Amber allows multiple ways to back up your private key. As most users would expect, you can get your standard nsec and copy/paste it to a password manager, but you can also obtain your private key as a list of mnemonic seed words, an encrypted version of your key called an ncryptsec, or even a QR code of your nsec or ncryptsec.

Additionally, in order to gain access to this information, Amber requires you to enter your device's PIN or use biometric authentication. This isn't cold-storage level protection for your private key by any means, especially since your phone is an internet connected device and does not store your key within a secure element, but it is about as secure as you can ask for while having your key accessible for signing Nostr events.

Tor Support

While Amber does not have Tor support within the app itself, it does support connecting to Tor through Orbot. This would be used with remote signing so that Amber would not connect directly over clearnet to the relay used for communication with the Nostr app requesting the signature. Instead, Amber would connect through Tor, so the relay would not see your IP address. This means you can utilize the remote signing option without compromising your anonymity.

Additional Security

Amber allows the user the option to require either biometric or PIN authentication before approving signing requests. This can provide that extra bit of assurance that no one will be able to sign events using your private key if they happen to gain access to your phone. The PIN you set in Amber is also independent from the PIN to unlock your device, allowing for separation of access.

Can My Grandma Use It?

Score: 4.6 / 5 (Updated 4/21/2025)

At the end of the day, Amber is a tool for those who have some concept of the importance of protecting their private key by not pasting it into every Nostr client that comes along. This concept in itself is not terribly approachable to an average person. They are used to just plugging their password into every service they use, and even worse, they usually have the same password for everything so they can more readily remember it. The idea that they should never enter their "Nostr password" into any Nostr application would never occur to them unless someone first explained how cryptography works related to public/private key pairs.

That said, I think there can be some improvements made to how users are introduced to these concepts, and that a signer application like Amber might be ideal for the job. Considering Amber as a new user's first touch-point with Nostr, I think it holds up well, but could be somewhat streamlined.

Upon opening the app, the user is prompted to either use their existing private key or "Create a new Nostr account." This is straightforward enough. "Account" is not a technically correct term with Nostr, but it is a term that new users would be familiar with and understand the basic concept.

The next screen announces that the account is ready, and presents the user with their public key, explaining that it is "a sort of username" that will allow others to find them on Nostr. While it is good to explain this to the user, it is unnecessary information at this point. This screen also prompts the user to set a nickname and set a password to encrypt their private key. Since the backup options also allow the user to set this password, I think this step could be pushed to a later time. This screen would better serve the new user if it simply prompted them to set a nickname and short bio that could be saved to a few default relays.

Of course, Amber is currently prompting for a password to be set up-front because the next screen requires the new user to download a "backup kit" in order to continue. While I do believe it is a good idea to encourage the creation of a backup, it is not crucial to do so immediately upon creation of a new npub that has nothing at stake if the private key is lost. This is something the UI could remind the user to do at a later time, reducing the friction of profile creation, and expediting getting them into the action.

Outside of these minor onboarding friction points, I think Amber does a great job of explaining to the user the purpose of each of its features, all within the app and without any need to reference external documentation. As long as the user understands the basic concept that their private key is being stored by Amber in order to sign requests from other Nostr apps, so they don't have to be given the private key, Amber is very good about explaining the rest without getting too far into the technical weeds.

The most glaring usability issue with Amber is that it isn't available in the Play Store. Average users expect to be able to find applications they can trust in their mobile device's default app store. There is a valid argument to be made that they are incorrect in this assumption, but that doesn't change the fact that this is the assumption most people make. They believe that applications in the Play Store are "safe" and that anything they can't install through the Play Store is suspect. The prompts that the Android operating system requires the user to approve when installing "unknown apps" certainly doesn't help with this impression.

Now, I absolutely love the Zapstore from franzap, but it doesn't do much to alleviate this issue. Users will still need to be convinced that it is safe to install the Zapstore from the GitHub repo, and then install Amber from there. Furthermore, this adds yet another step to the onboarding process.

Instead of:

• Install Amber
• Set up your keys
• Install the client you want to use
• Log in with Amber

The process becomes:

• Go to the Zapstore GitHub and download the latest version from the releases page.
• Install the APK you downloaded, allowing any prompt to install unknown apps.
• Open Zapstore and install Amber, allowing any prompt to install unknown apps again.
• Open Amber and set up your keys.
• Install the client you want to use
• Log in with Amber

An application as important as Amber for protecting users' private keys should be as readily available to the new user as possible. New users are the ones most prone to making mistakes that could compromise their private keys. Amber should be available to them in the Play Store.

UPDATE: As of version 3.2.8 released on 4/21/2025, the onboarding flow for Amber has been greatly improved! Now, when selecting to set up a new "account" the user is informed on the very next screen, "Your Nostr account is ready!" and given their public key/npub. The only field the user must fill in is their "nickname"/display name and hit "Continue."

From there the user is asked if they want Amber to automatically approve basic actions, or manually approve each app, and then they are shown a new Applications screen, with a prompt to create a backup of their account. This prompt persists until the user has done so.

As you can see, the user is also encouraged to find applications that can be used with Amber with links to nostrapps.com and the Zapstore.

Thanks to these updates, Amber is now the smoothest and most user-friendly onboarding experience I have seen for Nostr to date. Sure, it doesn't have anything for setting up a profile picture or lightning address, but that is better done in a client like Amethyst or YakiHonne, anyway. Just tap "create," type in a handle to call yourself, and you're done!

How do UI Look?

Score: 4.5 / 5

Amber's UI can be described as clean but utilitarian. But then, Amber is a tool, so this is somewhat expected. It is not an app you will be spending a lot of time in, so the UI just needs to be serviceable. I would say it accomplishes this and then some. UI elements are generally easy to understand what they do, and page headings fill in the gaps where that is not the case.

I am not the biggest fan of the color-scheme, particularly in light-mode, but it is not bad in dark-mode at all, and Amber follows whatever theme you have set for your device in that respect. Additionally, the color choice does make sense given the application's name.

It must also be taken into consideration that Amber is almost entirely the product of a single developer's work. He has done a great job producing an app that is not only useful, but pleasant to interact with. The same cannot be said for most utility apps I have previously used, with interfaces that clearly made good design the lowest priority. While Amber's UI may not be the most beautiful Nostr app I have seen, design was clearly not an afterthought, either, and it is appreciated.

Relay Management

Score: 4.9 / 5

Even though Amber is not a Nostr client, where users can browse notes from their favorite npubs, it still relies heavily on relays for some of its features. Primarily, it uses relays for communicating with other Nostr apps for remote signing requests. However, it also uses relays to fetch profile data, so that each private key you add to Amber will automatically load your chosen username and profile picture.

In the relay settings, users can choose which relays are being used to fetch profile data, and which relays will be used by default when creating new remote signing connection strings.

The user can also see which relays are currently connected to Amber and even look at the information that has been passed back and forth on each of those active relays. This information about actively connected relays is not only available within the application, but also in the notification that Amber has to keep in your device's notification tray in order to continue to operate in the background while you are using other apps.

Optionality is the name of the game when it comes to how Amber handles relay selection. The user can just stick with the default signing relay, use their own relay as the default, or even use a different relay for each Nostr application that they connect to for remote signing. Amber gives the user an incredible amount of flexibility in this regard.

In addition to all of this, because not all relays accept the event types needed for remote signing, when you add a relay address to Amber, it automatically tests that relay to see if it will work. This alone can be a massive time saver, so users aren't trying to use relays that don't support remote signing and wondering why they can't log into noStrudel with the connection string they got from Amber.

The only way I could see relay management being improved would be some means of giving the user relay recommendations, in case they want to use a relay other than relay.nsec.app, but they aren't sure which other relays will accept remote signing events. That said, most users who want to use a different relay for signing remote events will likely be using their own, in which case recommendations aren't needed.

Current Users' Questions

The AskNostr hashtag can be a good indication of the pain points that other users are currently having with any Nostr application. Here are some of the most common questions submitted about Amber in the last two months.

nostr:nevent1qqsfrdr68fafgcvl8dgnhm9hxpsjxuks78afxhu8yewhtyf3d7mkg9gpzemhxue69uhhyetvv9ujumn0wd68ytnzv9hxgq3qkgh77xxt7hhtt4u528hecnx69rhagla8jj3tclgyf9wvkxa6dc0sxp0e6m

This is a good example of Amber working correctly, but the app the user is trying to log into not working. In my experience with #Olas in particular, it sometimes allows remote signer login, and sometimes doesn't. Amber will receive the signing request and I will approve it, but Olas remains on the login screen.

If Amber is receiving the signing requests, and you are approving them, the fault is likely with the application you are trying to log into.

That's it. That's all the repeated questions I could find. Oh, there were a few one-off questions where relay.nsec.app wouldn't connect, or where the user's out-of-date web browser was the issue. Outside of that, though, there were no common questions about how to use Amber, and that is a testament to Amber's ease of use all on its own.

Wrap Up

If you are on Android and you are not already using Amber to protect your nsec, please do yourself a favor and get it installed. It's not at all complicated to set up, and it will make trying out all the latest Nostr clients a safe and pleasant experience.

If you are a client developer and you have not added support for NIP-55 or NIP-46, do your users the courtesy of respecting the sanctity of their private keys. Even developers who have no intention of compromising their users' keys can inadvertently do so. Make that eventuality impossible by adding support for NIP-55 and NIP-46 signing.

Finally, I apologize for the extended time it took me to get this review finished. The time I have available is scarce, Nostr is distracting, and greenart7c3 kept improving Amber even as I was putting it through its paces over the last two months. Keep shipping, my friend! You have made one of the most useful tools we have seen for Nostr to date!

Now... What should I review next?