Glossary

Short definitions of Swarm-specific terms used throughout this book. Each entry links to the chapter where the concept is developed in full.

BMT (Binary Merkle Tree)

The hash construction Swarm uses to address chunks. Operates on 4 KiB blocks with keccak256 as the underlying hash. Produces a 32-byte address per chunk. The structural alternative to a flat sha-256 hash.

Batch (postage batch)

A pre-funded allowance of chunk-storage capacity bought on-chain. Identified by a 32-byte ID. Every chunk uploaded to Swarm needs to be stamped with a batch; when the batch expires, storer nodes eventually drop the chunks. See Postage batches and re-seeding.

Chunk

The unit of storage in Swarm — up to 4 KiB of bytes, addressed by its BMT hash. Everything in Swarm (files, manifests, feed updates) is ultimately a graph of chunks.

Deferred upload

Bee’s default upload mode: the API accepts your data, returns the reference immediately, and pushes the chunks into the network in the background. Fast but means there’s a window where the reference exists locally and isn’t yet retrievable network-wide. See “My upload looks lost”.

Feed

Swarm’s mutable-name primitive — the analog of IPNS / DNSLink. Identified by an (owner, topic) pair where owner is a 20-byte Ethereum address and topic is a 32-byte hash. Resolved via GET /feeds/{owner}/{topic}. See Swarm references vs IPFS CIDs.

Gateway (public gateway)

A public Bee node exposed over HTTPS that serves GET /bzz/{ref}/ without auth. bee-check --gateway <URL> HEAD-probes one as an external retrievability vantage. Default is https://api.gateway.ethswarm.org.

Manifest

A Mantaray-encoded trie stored as a graph of chunks. Maps paths (like file paths) to chunk references. What GET /bzz/{ref}/path walks. See Manifests and per-chunk drill-down.

Mantaray

The serialization format used for manifests. Each node fits in one chunk and has up to 256 forks (one per first-byte of a child path). Nodes can also carry a target_address pointing at content chunks.

Neighborhood

The first byte of an overlay or chunk address, by convention used to describe “where in the address space” something lives. A chunk in neighborhood 0x4a is one whose address starts 0x4a…; storer nodes with overlays starting 0x4a… are the chunk’s primary neighbors. See Proximity.

Overlay (overlay address)

A node’s 32-byte identifier in the same address space as chunk references. Determines which chunks the node is responsible for. GET /addresses returns it. bee-check surfaces each vantage’s overlay so you can read its neighborhood.

PO (proximity order)

The number of leading bits two 32-byte values share. PO 0 = no shared bits; PO 8 = same first byte (same neighborhood); PO 256 = identical. The closeness metric in Swarm’s address space. See Proximity.

Reference

A 32-byte (64-hex) or 64-byte (128-hex, encrypted) Swarm address. Can point at a raw chunk, a manifest root, or a feed update. The input bee-check takes.

Re-seed

Re-uploading a reference’s chunks under a fresh postage batch, typically to refresh stamps before a batch expires. bee-check --reseed --stamp <id> does the pre-flight + PUT /stewardship/{ref} flow. See Postage and re-seeding.

SOC (single-owner chunk)

A chunk whose address is (owner_address, topic)-derived rather than content-derived. The substrate underneath feeds — each feed update is a SOC. Not directly addressed by bee-check today.

Stamp

The cryptographic proof that a chunk’s storage is paid for by a specific postage batch. Storer nodes only keep chunks with valid stamps; expired-batch chunks are eventually garbage-collected.

Stewardship probe

The GET /stewardship/{ref} endpoint a Bee node exposes. Walks the manifest at ref and tries to fetch every chunk through the network retrieval path, returning { "isRetrievable": true|false }. Different from /bzz which serves from local store when possible. See The stewardship probe.

Vantage

In bee-check, one --bee URL — a single perspective on retrievability. Multi-vantage probing samples retrievability from multiple points in the network. See Multi-vantage.