How do I identify Tabstack?

Look for `Mozilla-Tabstack/1.0 (+https://tabstack.ai)` in the User-Agent header.

Mozilla-Tabstack AI Crawler Guide

What is Mozilla-Tabstack?

Mozilla-Tabstack is the user agent for Tabstack, a web execution and data transformation API from Mozilla. Developers use it to have AI systems research, extract data and complete browser tasks on live sites.

Mozilla's access control documentation says every Tabstack request carries User-Agent: Mozilla-Tabstack/1.0 (+https://tabstack.ai). It respects robots.txt directives that are explicitly addressed to that user agent. Blocked paths stop immediately, requests fail fast without retries, and robots.txt results are cached.

A wildcard * rule is not enough: Tabstack only responds to explicit blocks aimed at its own token. Mozilla publishes no IP ranges or signatures for it in that documentation.

Relevant for AI search

Is Mozilla-Tabstack relevant for AI search?

Yes. Tabstack reads and acts on web pages for AI agents, so it decides whether those agents can use your content.

Tabstack is Mozilla's API for AI agents that need to research, extract and automate tasks on the web. Mozilla says it does not use requests or content to train models. A block stops agents built on Tabstack from reading your pages, so they answer from other sources.

How to handle Mozilla-Tabstack

Add a group that names Tabstack to block it:

User-agent: Mozilla-Tabstack
Disallow: /

For specific paths, list Disallow: /private/ lines in the same group. Mozilla says it ignores generic * rules, so a catch-all block will not stop it. There is no published way to verify a request, so rely on the user-agent string and rate limits.

Examples

A developer uses Tabstack to extract pricing tables from a vendor site for an agent workflow.
A site owner adds a `Mozilla-Tabstack` group to keep admin paths out of agent traffic.