NFT Metadata (2025): JSON, IPFS & Best Practices

Structure nft metadata correctly for ERC-721/1155, host it reliably, prevent rug-pulls, and keep creator privacy. This guide covers JSON fields, traits, on-chain vs off-chain storage, pinning, and CLI automation.

ERC-721ERC-1155IPFS/Arweave2025

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Reliability

Immutable URIs

Rug-pull riskLow (if pinned)

Privacy

Image EXIF

Leak chanceAvoidable

Compatibility

Marketplaces

Schema matchHigh

What is NFT metadata?

NFT metadata is a JSON file referenced by tokenURI. It contains human-readable fields (name, description), media links (image, animation_url) and attributes used for traits and filters on marketplaces.

{
  "name": "Wave #1",
  "description": "Generative ocean pattern",
  "image": "ipfs://bafy.../wave1.png",
  "animation_url": "ipfs://bafy.../wave1.mp4",
  "attributes": [
    { "trait_type": "Palette", "value": "Teal" },
    { "trait_type": "Rarity", "value": "Epic" }
  ]
}

Tip

Prefer ipfs:// or Arweave URIs in metadata. HTTP links can change or disappear.

JSON schema for ERC-721 & ERC-1155

Common fields

Used by most marketplaces

name, description, external_url
image (PNG/JPEG/GIF/SVG), animation_url (video/HTML)
attributes array for traits (strings or numbers)
background_color (hex), youtube_url (optional)

Hosting options: IPFS vs Arweave vs HTTP

Option	Pros	Cons	Best for
IPFS (+ pinning)	Content-addressed, cheap, decentralized gateways	Needs pinning/redundancy	Most collections
Arweave	Permanent storage, TX-anchored	Upfront cost, larger files pricey	Long-term archives
HTTP/S3	Simple, fast CDN	Mutable, central point of failure	Internal previews, staging

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On-chain vs Off-chain metadata

On-chain

Max permanence

Store JSON or data URI directly in the contract
Great for tiny SVG/JSON, generative art
Higher gas, update-unfriendly

Off-chain

Flexible & cheap

Host on IPFS/Arweave, set tokenURI to the CID
Pin across multiple providers
Use content hashes for verification

Traits & rarity

Use attributes for filterable traits. Stick to consistent naming and value types. Numeric traits should be numbers, not strings. Avoid leaking private data in attributes (e.g., GPS).

"attributes": [
  { "trait_type": "Background", "value": "Ocean" },
  { "trait_type": "Glow", "display_type": "boost_percentage", "value": 25 },
  { "trait_type": "Level", "display_type": "number", "value": 7 }
]

Tools & generators

Common steps

End-to-end

Generate artwork & export to lossless formats
Scrub image EXIF (see privacy tip below)
Create JSON metadata programmatically
Upload media → get CID → reference in JSON
Upload JSON → set tokenURI → pin

CLI automation

Generate JSON

Node.js script (example)

// generate.js
const fs = require('fs');
const items = [
  { id: 1, name: 'Wave #1', imageCid: 'bafy...1', palette: 'Teal' },
  { id: 2, name: 'Wave #2', imageCid: 'bafy...2', palette: 'Purple' }
];
for (const it of items) {
  const meta = {
    name: it.name,
    description: 'Generative ocean pattern',
    image: 'ipfs://' + it.imageCid,
    attributes: [{ trait_type: 'Palette', value: it.palette }]
  };
  fs.writeFileSync(`./metadata/${it.id}.json`, JSON.stringify(meta, null, 2));
}

Pin & verify

API or CLI

# ipfs-cli examples
ipfs add --cid-version=1 --pin ./images/*
ipfs add --cid-version=1 --pin ./metadata/*

# Verify that each tokenURI CID exists
# and that image CIDs referenced by JSON resolve via a gateway.

Image privacy: remove EXIF before minting

Photos often include hidden EXIF/GPS, camera serials, and authoring software tags. Once minted and replicated to IPFS, that data can spread forever. Always sanitize images before you upload.

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FAQ

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Ship trustworthy NFTs — and protect creator privacy

Use immutable URIs, pin your CIDs, validate JSON, and scrub image EXIF before minting. Fewer surprises after launch.

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