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

meta:
  title: ai.txt Specification
  description: The canonical specification for ai.txt files - AI usage permissions and intent signals.
  version: "1.7.0"
  versionDate: "2026-05-11"
  canonicalUrl: https://www.ai-visibility.org.uk/specifications/ai-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

specification:
  filename: ai.txt
  location: Website root directory
  urlPattern: https://example.com/ai.txt
  mimeType: text/plain
  encoding: UTF-8
  purpose: Declare how AI systems should interact with and represent the organisation. Defines what AI may and must not do when processing, citing, or generating content about the entity.

  format:
    type: Structured text
    description: Section-based plain text with bracketed section headers
    syntax:
      sections: "[section-name]"
      comments: "# Comment text"
      keyValue: "key: value"
      lists: "- list item"

  sections:
    required:
      - name: "[identity]"
        description: Business identifier linking this file to the organisation
        fields:
          - field: name
            description: Official organisation name
            required: true
          - field: url
            description: Canonical website URL
            required: true

      - name: "[permissions]"
        description: What AI systems are permitted to do
        format: List of permitted actions

      - name: "[restrictions]"
        description: What AI systems must not do
        format: List of prohibited actions

    recommended:
      - name: "[attribution]"
        description: How AI systems should attribute information from this source
        fields:
          - field: required
            description: Whether attribution is required (yes/no)
            example: "yes"
          - field: format
            description: Preferred citation format
            example: "According to [Organisation Name]..."

      - name: "[contact]"
        description: Contact information for AI-related queries
        fields:
          - field: ai-queries
            description: Email for AI-related questions

      - name: "[scope]"
        description: Define the scope of these permissions
        fields:
          - field: applies-to
            description: What content these rules apply to

    optional:
      - name: "[licensing]"
        description: Content licensing information
        fields:
          - field: content-license
            description: License for website content
          - field: ai-training
            description: Whether content may be used for AI training

      - name: "[metadata]"
        description: File metadata
        fields:
          - field: version
            description: Version of this ai.txt file
          - field: last-updated
            description: Date of last update

  permissionTypes:
    common:
      - cite-with-attribution
      - summarise-content
      - answer-questions
      - describe-services
      - provide-contact-information
    conditional:
      - quote-with-source
      - recommend-conditionally

  restrictionTypes:
    common:
      - imply-endorsement
      - generate-fake-quotes
      - provide-specific-advice
      - guarantee-outcomes
      - make-claims-beyond-scope

  validation:
    rules:
      - MUST include [identity] section with name and url
      - MUST include [permissions] section
      - MUST include [restrictions] section
      - MUST be valid UTF-8 encoded plain text
      - Section headers MUST use square brackets
      - Key-value pairs MUST use colon separator
    commonErrors:
      - Missing required sections
      - Inconsistent section header format
      - Contradictory permissions and restrictions
      - Missing identity linkage
      - Overly vague permission language

  relationships:
    ai.json: Machine-parseable equivalent - should contain consistent information
    llms.txt: Identity information must match
    identity.json: Organisation details must be consistent
    robots.txt: Complements crawler access rules with behavioural guidance

example:
  url: https://www.ai-visibility.org.uk/specifications/examples/ai.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: Added expanded optional sections (scope, training, data-retention, updates) and Content Not Permitted guidance. Clarifies what should not be included in ai.txt files.
  - version: "1.0.0"
    date: "2026-01-12"
    changes: Initial specification release. Establishes canonical structure for ai.txt files with permissions, restrictions, and attribution sections.
