What a good website does.
A platform-agnostic specification of all the technical details that matter for a website, from <title>to /.well-known/security.txt to WCAG contrast. Written for humans and agents.
How to use this site
- 01
Audit
Run the checklist against your site, or let your agent do it. Each item is a yes/no.
- 02
Learn
Open any item for what it is, why it matters, and how to implement it.
- 03
Improve
Fix what's missing on your site, then re-check.
Recently changed
Full changelog →Principles
What every page here is built on.
Standards, not opinions
Each topic links back to the source standard: WHATWG, W3C, IETF RFCs, WCAG, MDN, and the organisations defining the modern web.
Platform agnostic
Whether you ship WordPress, Drupal, TYPO3, Next.js, Astro, Hugo, a Django app, or plain HTML, the spec is the spec. Implementation hints follow it, not the other way round.
Built in the open
Every page has an Edit on GitHub link. PRs welcome. Sources credited on every page.
Let your agent query the spec.
The whole spec is available as an open MCP server (read-only, no auth), plus a published Agent Skill that teaches any compatible agent when and how to use it. Per-page Markdown is available via /llms.txt and Accept: text/markdown on any spec URL.
{
"mcpServers": {
"specification-website": {
"transport": "http",
"url": "https://mcp.specification.website/mcp"
}
}
}Categories
Ten areas, mapped to widely-accepted standards.
Foundations
18 topicsThe HTML, head, and document basics every page needs.
SEO
14 topicsSearch visibility — robots.txt, sitemaps, canonicals, structured data.
Accessibility
25 topicsWCAG-aligned rules so people of all abilities can use the site.
Security
17 topicsHeaders, transport, and policies that keep visitors safe.
Well-Known URIs
10 topicsStandard, agreed-upon paths under /.well-known/.
Agent Readiness
20 topicsThings that make a site legible to AI agents and crawlers.
Performance
25 topicsCore Web Vitals, caching, images, fonts, network behaviour.
Privacy
6 topicsConsent, signals, and respecting visitor choice.
Resilience
6 topicsGraceful failure — error pages, offline, redirects.
Internationalisation
13 topicsLanguage, locale, direction, and translated content.
Run the full checklist
Every topic as a tickable yes/no audit →
Browse every topic
All 154 entries across the ten categories →