# llms.txt Specification
# Version: 1.7.0
# https://www.ai-visibility.org.uk/specifications/llms-txt/

meta:
  title: llms.txt Specification
  description: The canonical specification for llms.txt files - AI-readable business identity and context files.
  version: "1.7.0"
  versionDate: "2026-05-11"
  canonicalUrl: https://www.ai-visibility.org.uk/specifications/llms-txt/
  publisher:
    name: 365i
    url: https://www.365i.co.uk/
  license:
    name: Creative Commons Attribution 4.0 International
    identifier: CC-BY-4.0
    url: https://creativecommons.org/licenses/by/4.0/
  datePublished: "2026-01-12T00:00:00Z"
  dateModified: "2026-05-11T00:00:00Z"
  language: en-GB
  basedOn:
    name: llmstxt.org Convention
    url: https://llmstxt.org/

specification:
  filename: llms.txt
  location: Website root directory
  urlPattern: https://example.com/llms.txt
  mimeType: text/plain
  encoding: UTF-8
  purpose: Provide AI systems with a comprehensive, machine-readable overview of an organisation's identity, purpose, services, and context.

  format:
    type: Markdown
    description: Structured Markdown text following llmstxt.org convention
    structure:
      title:
        syntax: "# Title"
        description: H1 heading with organisation or website name
        required: true
      summary:
        syntax: "> Blockquote summary"
        description: Brief blockquote immediately after title summarising the organisation
        required: true
      sections:
        syntax: "## Section Name"
        description: H2 headings for each major section
        required: true

  sections:
    required:
      - name: Summary
        description: Blockquote appearing directly after the H1 title providing a concise overview
      - name: About
        description: Detailed description of the organisation, its purpose, and what it does
      - name: Contact
        description: Primary contact information including email, phone, and address

    recommended:
      - name: Services
        description: List of services or products offered
      - name: We Do Not
        description: Explicit exclusions - services not offered or claims that should not be made
      - name: Locations
        description: Geographic presence and service areas
      - name: Key People
        description: Notable individuals associated with the organisation
      - name: Links
        description: Important URLs including other AI discovery files

    optional:
      - name: History
        description: Founding date and organisational history
      - name: Awards
        description: Notable recognitions or certifications
      - name: Custom sections
        description: Additional sections relevant to the organisation

  validation:
    rules:
      - MUST begin with exactly one H1 heading
      - MUST include blockquote summary immediately after H1
      - MUST use H2 headings for all sections
      - MUST be valid UTF-8 encoded plain text
      - SHOULD use Markdown list syntax for enumerated items
      - SHOULD use Markdown link syntax for URLs
    commonErrors:
      - Missing blockquote summary after title
      - Using multiple H1 headings
      - Inconsistent heading hierarchy
      - Including HTML markup instead of Markdown
      - Encoding issues with special characters

  relationships:
    llm.txt: Should contain identical content for compatibility
    llms.html: Should present equivalent information in HTML format
    identity.json: Should have consistent identity information
    ai.txt: Complements with permission and restriction declarations

example:
  url: https://www.ai-visibility.org.uk/specifications/examples/llms.txt
  business: Horizon Strategic Consulting

versionHistory:
  - version: "1.7.0"
    date: "2026-05-11"
    changes: "Phase 6 standardisation release. Added /specifications/roadmap/ (theme-pegged forward plan with Active/Next/Future/On hold status flags), /specifications/extensions/ (rules for experimental x- prefixed files and the promotion path), and /specifications/i18n-a11y/ (multi-language publication, locale-tagged identity fields, RTL handling, accessibility of llms.html). Added the Discovery: directive to the robots-ai.txt specification (publishers MAY advertise AI Discovery Files on the same host). Added a formal media-type stance to the HTTP behaviour page (existing IANA types, no bespoke registrations). Expanded the file integrity and signing section on the security and privacy page with four candidate mechanisms, cross-cutting concerns, and interim publisher / consumer guidance. The Discovery: directive is the only normative addition to publisher behaviour; all other additions are forward-looking documentation."
  - version: "1.6.0"
    date: "2026-05-11"
    changes: "Phase 5 standardisation release. Added /specifications/related-standards/ (positioning vs llmstxt.org, IETF AI Preferences, robots.txt, Schema.org, BCP 14, JSON Schema 2020-12, SemVer) and /specifications/implementations/ (public record of conformant implementations, IETF-style). Added an explicit llmstxt.org backward-compatibility statement to the llms.txt specification. Added a formal multi-domain and subdomain scoping rule to both the llms.txt and identity.json specifications (host-scoped files, cross-host identity asserted via sameAs). No normative requirements changed for existing publishers; the new scoping rules formalise behaviour the specification already implied."
  - version: "1.5.0"
    date: "2026-05-11"
    changes: "Phase 4 standardisation release. Added /specifications/processing-model/ (seven-stage algorithm for conformant consumers), /specifications/consumer-guidance/ (what AI systems should do with AI Discovery Files), /specifications/test-vectors/ (canonical test suite framing), and reference-implementation framing on the AI Visibility Checker. No normative requirements changed."
  - version: "1.4.0"
    date: "2026-05-11"
    changes: "Phase 3 standardisation release. Added /specifications/versioning/ (Semantic Versioning 2.0.0 commitments, deprecation timeline, lifecycle), /specifications/governance/ (proposal lifecycle, editorial process, working principles), /specifications/security-privacy/ (trust model, content-injection patterns, GDPR considerations, integrity primitives roadmap), and /specifications/http-behaviour/ (status codes, redirects, soft-404 detection, caching, rate limits). No normative requirements changed."
  - version: "1.3.0"
    date: "2026-05-11"
    changes: "Phase 2 standardisation release. Added formal conformance specification (Essential / Recommended / Complete classes). Published machine-readable registry at /specifications/registry.json, spec meta-schema, and validator-output schema. Introduced versioned JSON Schema URLs (/v1/) alongside unversioned 'latest' aliases. Added optional BCP 47 language declaration field across all applicable AI Discovery Files. No normative requirements changed."
  - version: "1.2.0"
    date: "2026-05-10"
    changes: "Phase 1 standardisation release. Added 'Status of This Document' block (Stable). Normalised normative requirement keywords to uppercase per RFC 2119 and RFC 8174. Added References section linking to /specifications/conventions/ and /licensing/. No normative requirements changed."
  - version: "1.1.1"
    date: "2026-02-13"
    changes: Added AI Visibility Directory registration guidance. Minor documentation update.
  - version: "1.1.0"
    date: "2026-01-14"
    changes: 'Expanded optional sections with specific examples (Team, Locations, Certifications, Awards, Partners, Industries). Added "Content Not Permitted" section to clarify what must not be included.'
  - version: "1.0.0"
    date: "2026-01-12"
    changes: Initial publication. Establishes canonical structure for llms.txt files based on llmstxt.org convention with enhanced business identity requirements.
