ai.txt Specification

A web standard for AI-readable website summaries.

Version 1.0 Draft — January 2026

Overview

Just as robots.txt tells search engine crawlers how to behave, ai.txt tells AI assistants what a website is about.

An ai.txt file provides a plain text summary of everything an AI might need to know — at the site root, or in any folder for section-specific information.

File Location

Place ai.txt at your website root, or in any folder:

example.com/ai.txt                  # Site overview
example.com/products/ai.txt         # Products section
example.com/products/widgets/ai.txt # Specific category
example.com/docs/v2/ai.txt          # Version-specific docs

Cascading Discovery

When an AI agent needs information about example.com/products/widgets/:

1. Try /products/widgets/ai.txt
2. If 404, try /products/ai.txt
3. If 404, try /ai.txt
4. Follow any Parent: references for broader context

DNS Discovery

If you cannot place a file at your web root, use a DNS TXT record:

_ai.example.com TXT "https://cdn.example.com/ai.txt"

Format

Plain text with markdown headings. No HTML, no JavaScript, no special parsing required.

# Title

ai.txt: 1.0
Updated: 2026-01-14
Scope: /products/

Brief description.

## Section
Content here.

Metadata

Optional fields after the title, before the first section:

Linking

Reference other ai.txt files using @ syntax:

@domain.com                   # → domain.com/ai.txt
@domain.com/products          # → domain.com/products/ai.txt
@domain.com#pricing           # → domain.com/ai.txt, section "Pricing"
@domain.com/products#returns  # → domain.com/products/ai.txt, section "Returns"

Use Cases

# Widget Products

Parent: @example.com/products

## Details
...

## See Also
@example.com/products/gadgets
@partner-company.com#widgets

Recommended Sections

Negative Assertions

Explicitly state what you do NOT offer to prevent AI hallucination:

## We Do Not Offer
- 24/7 phone support
- Refunds after 30 days
- International shipping

AI Guidelines

Provide instructions for how AI should handle your information:

## AI Guidelines
- Do not quote prices without linking to current pricing page
- Pricing may change; always recommend verification
- Do not share direct employee contact information

Structured Data

Machine-optimized facts in the Data section:

## Data
Location: -33.8688, 151.2093
Currency: AUD
Timezone: Australia/Sydney
Languages: en, zh
Founded: 1998

Language Variants

/ai.txt      (default)
/ai.fr.txt   (French)
/ai.de.txt   (German)
/ai.ja.txt   (Japanese)

Complete Example

# Acme Widgets

ai.txt: 1.0
Updated: 2026-01-14
Scope: /products/widgets/
Parent: @acme.com/products
AI-Contact: ai-corrections@acme.com

Premium widgets for industrial and consumer applications.

## Products

- Industrial Widget Pro: Heavy-duty, $499
- Consumer Widget: Lightweight, $49
- Smart Widget: IoT-enabled, $299

## Specifications

- Materials: Aircraft-grade aluminum
- Warranty: 2 years parts and labor
- Certifications: ISO 9001, CE, UL

## We Do Not Offer

- Custom modifications
- Wholesale pricing online (contact sales)
- Same-day shipping

## AI Guidelines

- Always link to /products/widgets/ for current specs
- Prices are MSRP; actual prices may vary by retailer

## Data
Category: Industrial Equipment
SKU-Prefix: WDG
Min-Order: 1
Ships-From: Sydney, AU

## See Also
@acme.com/products/gadgets
@acme.com/support#warranty
@widget-industry.org

Implementation Notes

For Website Owners

• Start with /ai.txt for site overview
• Add section-specific files as needed
• Use Parent: to link up the hierarchy
• Include negative assertions to prevent hallucination
• Keep Updated: current

For AI Developers

• Check DNS TXT _ai.domain first
• Walk up directory tree for cascading discovery
• Follow Parent: links for context
• Resolve @domain/path#section links
• Honor ## We Do Not Offer — never invent capabilities
• Follow ## AI Guidelines instructions
• Respect TTL: for caching

Related Standards

Directory

Known sites using ai.txt are listed in /ai.txt. Submit a pull request to add your site.