The ERC-721 NFT standard, explained for engineers — with a live on-chain viewer.

A minimalist, open-source resource for engineers who land here from a Google search and want to actually understand ERC-721 — the spec, the mechanics, the history, and how to inspect any NFT on-chain.

Live at erc721.xyz.

Available in English (/), 日本語 (/ja/), and 简体中文 (/zh/). PRs adding more languages welcome — see CONTRIBUTING.md.

• / — landing page with the interface in 9 lines.
• /spec — full ERC-721 spec, function selectors, interface IDs, metadata schema, related EIPs.
• /history — Quantum (2014) → today's blue chips, with representative images committed under public/images/history/.
• /viewer — paste a contract address + token ID, get the NFT. Works on Ethereum, Polygon, Base, and Arbitrum. No wallet, no backend.

• Astro 5 — minimal JS, static HTML output.
• Vanilla TypeScript for the interactive viewer (no React/framework runtime).
• Hand-rolled JSON-RPC client — selectors and ABI decoding inlined so engineers can read the actual mechanics.
• Public RPC endpoints by default (Cloudflare ETH, Polygon RPC, Base, Arbitrum). Users can paste their own Alchemy/Infura URL in the viewer.
• Public IPFS gateway (ipfs.io) by default; user-overridable.
• GitHub Pages deployment via GitHub Actions.

No tracking, no analytics, no wallets, no backend.

npm install
npm run dev      # http://localhost:4321
npm run build    # static output to ./dist
npm run preview  # preview the production build

Requires Node 20+.

Pushing to main triggers .github/workflows/deploy.yml, which builds the site with Astro and publishes dist/ to GitHub Pages.

To set up:

1. In the GitHub repo settings → Pages, set "Build and deployment" source to GitHub Actions.
2. Configure the custom domain erc721.xyz (the public/CNAME file is already in place).
3. Push to main — the action deploys automatically.

Issues and PRs are welcome — corrections, improvements, new content, and translations.

• See CONTRIBUTING.md for the full guide.
• For translations specifically, see the Adding a translation section.

MIT — see LICENSE.