BloomPersonal Blossom Media Server and Nostr Relay

What Is Bloom and Who Is It For?

Bloom is a server, not a social app. You do not use it to write posts or follow people. Instead, it stores the files that Nostr content refers to and passes events along to other users. Think of it as the back office of a Nostr presence: the place where your images, documents and other attachments live.

The program suits several kinds of users. Self-hosters who already run software at home or on a small server will recognize the model. Developers building Nostr clients or experimenting with the Blossom protocol can use Bloom as a local test target. Writers and small communities who want their media to stay under their own control may find it useful as well.

It is less suited to people who want a fully managed service. Running Bloom means you decide where files live, how much space they use and when backups happen. The tradeoff is control: nobody else can change your storage rules or remove your files without your involvement, but you also carry the responsibility of keeping the server working.

How Content Addressing Keeps Files Verifiable

Bloom identifies every file by its SHA-256 hash. The hash is computed from the file's contents, so the same file always produces the same identifier, and any change to the file produces a different one. This is called content addressing, and it is the reason Blossom links are reliable.

For a reader, the practical benefit is simple. If a file reaches you through a link that contains a hash, you can check whether the bytes you received match what the link promised. A server that alters an image or swaps a document cannot pass off the altered version under the original address.

The same mechanism helps when mirroring. A copy of a blob pulled from another server can be compared against its hash, so you know you are holding an exact duplicate. Content addressing does not hide anything or encrypt files, though. Anyone who knows the hash can ask for the file, so private material should be protected before it is uploaded.

Real-World Ways People Run a Personal Nostr Server

A common scenario is a writer who publishes long posts with images. Instead of relying on a third-party host, the writer runs Bloom on a Windows PC and points the Nostr client at it for media. If the writer later moves the blog to another platform, the media is still under their own control.

Another scenario is a small group that shares photos and documents among members. One member can run Bloom and mirror files from the others, so the group does not depend on a single contributor's device. Mirroring also gives the group a second copy if the original server goes offline.

Developers use Bloom as a local test environment. They can upload blobs, check hashes, try out blossom:// links and see how a client reacts to missing or mismatched files. Because the program runs on the developer's own machine, experiments stay private until they are deliberately shared. These uses are only examples; the best setup depends on how much you publish and how often you want your content available.

Where Bloom Fits in the Nostr Stack

Nostr works through a simple split of responsibilities. Clients are the apps people read and write with. Relays receive and forward signed events. Media servers hold the files that events refer to. Bloom covers two of these roles at once, acting as a Blossom media server and as a Nostr relay in a single program.

That combination is the main reason to consider it. With separate tools, you would need to install and maintain a relay and a file host, then connect them. Bloom reduces that to one application on one machine. Its background presence and Windows build make it easier to leave running without a dedicated server.

It does not replace clients. To post, read or manage your identity, you still need a Nostr client that supports the protocols Bloom implements. Bloom is the storage and distribution layer underneath those apps, which is why it works best alongside a client you already like.

Supported coins

Bloom is not a cryptocurrency wallet or a miner. Its documentation ties it to the Nostr network, and it uses SHA-256 hashing to identify files by their content. The name SHA-256 also appears in mining contexts, but in Bloom it serves the storage job described above, not mining.