CCBot
The crawler behind Common Crawl, a free public archive of the web that most open training corpora are built from.
17.5% of the 2,228 domains Domduck read on disallow it, against 14.1% on .
What blocking CCBot costs
The largest indirect one in the table. Common Crawl is an input to many models rather than one, so blocking CCBot removes you from a corpus you cannot enumerate, and it does so for every future model built on it.
What it does not cost
Archives already published keep the pages they already hold. Common Crawl does not retract past crawls.
It is also the oldest entry here, so a robots.txt written years ago for reasons unrelated to AI may already block it. Domduck reports what the file says today, not why it says it.
How to block it
or allow it explicitlyUser-agent: CCBot
Disallow: /To allow it and say so, use a bare Disallow: with nothing after it, which RFC 9309 defines as “nothing is disallowed”. That matters more than it looks: a file that never names an agent leaves it in a third state, neither allowed nor blocked, and a catch-all rule added later will block it without anyone deciding to.
Block rate over time
2 daysThe percentage of domains in the corpus whose robots.txt disallows CCBot, measured once per domain per pass. The denominator is how many domains were read that day and is stored with each point, so the line is not restated when the corpus grows.
The other seven
- OpenAI
- GPTBot
- OpenAI
- OAI-SearchBot
- Anthropic
- ClaudeBot
- Perplexity
- PerplexityBot
- Google-Extended
- Apple
- Applebot-Extended
- ByteDance
- Bytespider
How this page is made
The explanation above is written by a person. The numbers are computed from Domduck’s own daily reads of each domain’s robots.txt, parsed to RFC 9309 rather than searched for a string: a rule binds to the nearest preceding group of user-agent lines, the longest matching pattern wins, and Allow breaks a tie. No prefix matching is done, so a group naming Google is not treated as a policy about Google-Extended. What the collectors have read.