# IPFS glossary
Announcing is a function of the IPFS networking layer in libp2p, wherein a peer can tell other peers that it has data blocks available.
Bitswap is IPFS's central block exchange protocol. Its purpose is to request blocks from and send blocks to other peers in the network. More about Bitswap (opens new window)
BitTorrent is a communication protocol for peer-to-peer file sharing, which is used to distribute data and electronic files over the Internet. Also, the first file-sharing application to use the protocol. More about BitTorrent protocol (opens new window) and BitTorrent app (opens new window)
A Blockchain is a growing list of records, known as blocks, that are linked using cryptography. Each block contains a cryptographic hash of the previous block, a timestamp, and transaction data (generally represented as a Merkle tree). More about Blockchain (opens new window)
A Block is a binary blob of data, identified by a CID.
# Bootstrap Node
A Bootstrap Node is a trusted peer on the IPFS network through which an IPFS node learns about other peers on the network. More about Bootstrapping (opens new window)
# CID v0
Version 0 (v0) of the IPFS content identifier. This CID is 46 characters in length, starting with "Qm". Uses a base 58-encoded multihash, very simple but much less flexible than newer CIDs. More about CID v0 (opens new window)
# CID v1
Version 1 (v1) of the IPFS content identifier. This CID version contains some leading identifiers which provide for forward-compatibility. Able to support different formats for future versions of CID. More about CID v1 (opens new window)
A Conflict-Free Replicated Data Type (CRDT) is a type of specially-designed data structure used to achieve strong eventual consistency (SEC) and monotonicity (absence of rollbacks). More about CRDT (opens new window)
A Daemon is a computer program that typically runs in the background. The IPFS daemon is how you take your node online to the IPFS network. More about IPFS Daemon (opens new window)
A Directed Acyclic Graph (DAG) is a computer science data structure adapted for use with versioned file systems, blockchains, and for modeling many different kinds of information. More about DAG (opens new window)
The Datastore is the on-disk storage system used by an IPFS node. Configuration parameters control the location, size, construction, and operation of the datastore. More about Datastore (opens new window)
A Distributed Hash Table (DHT) is a distributed key-value store where keys are cryptographic hashes. In IPFS, each peer is responsible for a subset of the IPFS DHT. More about DHT (opens new window)
DNSLink is a protocol to link content and services directly from DNS. A DNSLink address looks like an IPNS address, but it uses a domain name in place of a hashed public key, like /ipns/mydomain.org. More about DNSLink (opens new window)
The Decentralized Web (DWeb) looks like today's World Wide Web, but it is built with new underlying technologies that support decentralization. It is much harder for any single entity (like a government or terrorist group) to take down any single webpage, website, or service, either by accident or on purpose.
The Filestore is a data store that stores the UnixFS data components of blocks as files on the file system instead of as blocks. This allows adding content to IPFS without duplicating the content in the IPFS datastore.
An IPFS Gateway acts as a bridge between traditional web browsers and IPFS. Through the gateway, users can browse files and websites stored in IPFS as if they were stored on a traditional web server. More about Gateway (opens new window)
# Garbage Collection
Garbage Collection (GC) is the process within each IPFS node of clearing out cached files and blocks. Nodes need to clear out previously cached resources to make room for new resources. Pinned resources are never deleted.
In computer science, a Graph is an abstract data type from the field of graph theory within mathematics. The Merkle-DAG used in IPFS is a specialized graph.
Graphsync is an alternative content replication protocol under discussion, similar to Bitswap. Like Bitswap, the primary job is to synchronize data blocks across peers. More about Graphsync (opens new window)
A Cryptographic Hash is a function that takes some arbitrary input (content) and returns a fixed-length value. The exact same input data will always generate the same hash as output. There are numerous hash algorithms. More about Hash (opens new window)
# Information Space
Information Space is the set of concepts, and relations among them, held by an information system. This can be thought of as a conceptual framework or tool for studying how knowledge and information are codified, abstracted, and diffused through a social system. More about Information Space (opens new window)
The InterPlanetary Linked Data (IPLD) model is a set of specifications in support of decentralized data structures for the content-addressable web. Key features are interoperable protocols, easily upgradeable, backward compatible. A single namespace for all hash-based protocols. More about IPLD (opens new window)
The InterPlanetary Name System (IPNS) is a system for creating and updating mutable links to IPFS content. IPNS allows for publishing the latest version of any IPFS content, even though the underlying IPFS hash has changed. More about IPNS (opens new window)
The libp2p project is a modular system of protocols, specifications, and libraries that enable the development of peer-to-peer network applications. It is an essential component of IPFS. More about libp2p (opens new window)
The Merkle-DAG is a computer science data structure used at the core of IPFS files/block storage. Merkle-DAGs create a hash to their content, known as a Content Identifier. More about Merkle-DAG (opens new window)
# Merkle Forest
Merkle Forest is a phrase coined to describe the distributed, authenticated, hash-linked data structures (Merkle trees) running technologies like Bitcoin, Ethereum, git, and BitTorrent. In this way, IPFS is a forest of linked Merkle trees. More about Merkle Forest (opens new window)
# Merkle Tree
A Merkle Tree is a specific type of hash tree used in cryptography and computer science, allowing efficient and secure verification of the contents of large data structures. Named after Ralph Merkle, who patented it in 1979. More about Merkle Tree (opens new window)
The Mutable File System (MFS) is a tool built into IPFS that lets you treat files like a normal name-based filesystem. You may add, edit, and remove MFS files while all link updates and hashes are taken care of for you. More about MFS (opens new window)
The Multiformats project is a collection of protocols that aim to future-proof systems today. A key element is enhancing format values with self-description. This allows for interoperability, protocol agility, and promotes extensibility. More about Multiformats (opens new window) and Multihash (opens new window)
A Path/Address is the method within IPFS of referencing content on the web. Addresses for content are path-like; they are components separated by slashes. More about Path/Address (opens new window)
In system architecture, a Peer is an equal player in the peer-to-peer model of decentralization, as opposed to the client-server model of centralization. See also Peer as Node
# Peer ID
A Peer ID is how each unique IPFS node is identified on the network. The Peer ID is created when the IPFS node is initialized and is essentially a cryptographic hash of the node's public key. More about Peer ID (opens new window)
Pinning is the method of telling an IPFS node that particular data is important and so it will never be removed from that node's cache. More about Pinning (opens new window)
Publish-subscribe (Pubsub) is an experimental feature in IPFS. Publishers send messages classified by topic or content, and subscribers receive only the messages they are interested in. More about Pubsub (opens new window)
The Relay is a means to establish connectivity between libp2p nodes (e.g., IPFS nodes) that wouldn't otherwise be able to establish a direct connection to each other. This may be due to nodes that are behind NAT, reverse proxies, firewalls, etc. More about Relay (opens new window)
The Repository (Repo) is a directory where IPFS stores all its settings and internal data. It is created with the
ipfs init command. More about Repo (opens new window)
A Self-certifying File System (SFS) is a distributed file system that doesn't require special permissions for data exchange. It is self-certifying because data served to a client is authenticated by the file name (which is signed by the server). More about SFS (opens new window)
# Signing (Cryptographic)
The signing of data cryptographically allows for trusting of data from untrusted sources. Cryptographically signed values can be passed through an untrusted channel, and any tampering of the data can be detected. More about Digital signature (opens new window)
The Swarm is a term for the network of IPFS peers with which your local node has connections. Swarm addresses are addresses that your local node will listen on for connections from other IPFS peers. More about Swarm addresses (opens new window)
In libp2p, transport refers to the technology that lets us move data from one machine to another. This may be a TCP network, a WebSocket connection in a browser, or anything else capable of implementing the transport interface.
The Unix File System (UnixFS) is the data format used to represent files and all their links and metadata in IPFS and is loosely based on how files work in Unix. Adding a file to IPFS creates a block (or a tree of blocks) in the UnixFS format. More about UnixFS (opens new window)