What is IPFS (InterPlanetary File System)?

A peer-to-peer protocol that stores and addresses files by their content rather than by their location.

nft images and metadata are often kept on IPFS, because storing large files directly on a blockchain is impractical. A file stays reachable only while some node continues to host it.

That last sentence is the one people skip. IPFS is not storage in the sense of a cloud provider you pay to keep something. It is an addressing and distribution system, and permanence is a service someone has to provide on top of it.

How it works

A conventional web address names a location: a server, a path, a file. Whatever that server returns is what you get, and if the server changes the file the address still resolves, now to different content.

IPFS names the content instead. A file is hashed, and that hash becomes its content identifier, usually called a CID. Asking the network for a CID means asking any peer that has the matching bytes, and when they arrive you can verify them yourself by rehashing. A CID cannot point at different content later, because different content would produce a different CID.

Retrieval works by peer discovery. Your client asks the network which peers hold the CID, connects to one, and downloads. Most people never run a client and use a gateway instead, an HTTP server that fetches from the network on their behalf, which is why NFT metadata frequently appears as a gateway link rather than a native address.

Persistence is the gap. A node keeps a file only while it is pinned, meaning explicitly marked to retain. Nodes discard unpinned data during garbage collection. Projects therefore either run their own pinning infrastructure, pay a pinning service, or rely on a network like Filecoin that pays for storage with contracts. If everyone stops pinning, the CID remains valid and resolves to nothing.

Example

Illustrative walkthrough. You buy an NFT whose on-chain token record points to a metadata CID. The metadata contains a name, attributes, and an image CID. Both files are held by a pinning service the project pays for. Two years later the project stops paying and no other node has pinned the files. The token still exists on chain, its CID is still recorded, and nothing about the blockchain has changed. The image no longer loads anywhere, because no peer holds the bytes. The pointer survived. The content did not.

Why it matters when you buy

If you are buying a token whose value depends on off-chain content, the question is who pins it and for how long, and that is answerable before purchase rather than after. More generally, the same reasoning applies to any project promising permanence: the claim is only as strong as the party paying for it. The coin pages and verify a token contract cover the checks that are actually verifiable.

Related terms

• nft: the most common use for these references
• hash: the function that produces a content identifier
• smart contract: where the pointer is usually recorded
• on chain off chain: the split this creates
• data availability: the equivalent problem for rollups
• block explorer: where you can read the stored pointer

Questions

Is a file on IPFS permanent?

No. It persists while at least one node pins it. Permanence is a service someone pays for, not a property of the protocol.

Can the file behind an NFT be changed?

Not if the token points to a content identifier, since changing the file changes the identifier. It can be changed if the token points to a mutable web address, which is common enough to be worth checking.

Do I need to run anything to view IPFS content?

No. Public gateways serve the content over ordinary HTTP, which is how most wallets and marketplaces display it. Running your own node just removes the dependency on that gateway.