Rank 808 in the Majestic Million · checked October 19, 2026
Does cancer.gov block AI crawlers?
No. As of October 19, 2026, cancer.gov's robots.txt allows all 17 AI crawlers we check everywhere. None of them is named in the file: they all follow its rules for every crawler (User-agent: *).
It has no llms.txt (HTTP 404). Its homepage is 10,592 tokens of raw HTML, 448 as Markdown (4.2%) and 55 pruned for the question “What is cancer.gov?”.
Each crawler, by its robots.txt rules
From https://www.cancer.gov/robots.txt (57 bytes, 1 user-agent groups), parsed per RFC 9309. Blocked: no path allowed. Partly blocked: some paths disallowed. The rule counts are those of the groups that apply.
| Crawler | Operator | Verdict | Rules that apply | Disallow rules | Allow rules |
|---|---|---|---|---|---|
| GPTBot | OpenAI | Allowed | Rules for all crawlers (*) | 0 | 0 |
| ChatGPT-User | OpenAI | Allowed | Rules for all crawlers (*) | 0 | 0 |
| OAI-SearchBot | OpenAI | Allowed | Rules for all crawlers (*) | 0 | 0 |
| ClaudeBot | Anthropic | Allowed | Rules for all crawlers (*) | 0 | 0 |
| Claude-User | Anthropic | Allowed | Rules for all crawlers (*) | 0 | 0 |
| Claude-SearchBot | Anthropic | Allowed | Rules for all crawlers (*) | 0 | 0 |
| anthropic-ai | Anthropic | Allowed | Rules for all crawlers (*) | 0 | 0 |
| PerplexityBot | Perplexity | Allowed | Rules for all crawlers (*) | 0 | 0 |
| Perplexity-User | Perplexity | Allowed | Rules for all crawlers (*) | 0 | 0 |
| Google-Extended | Allowed | Rules for all crawlers (*) | 0 | 0 | |
| Applebot-Extended | Apple | Allowed | Rules for all crawlers (*) | 0 | 0 |
| CCBot | Common Crawl | Allowed | Rules for all crawlers (*) | 0 | 0 |
| Bytespider | ByteDance | Allowed | Rules for all crawlers (*) | 0 | 0 |
| Amazonbot | Amazon | Allowed | Rules for all crawlers (*) | 0 | 0 |
| meta-externalagent | Meta | Allowed | Rules for all crawlers (*) | 0 | 0 |
| cohere-ai | Cohere | Allowed | Rules for all crawlers (*) | 0 | 0 |
| Diffbot | Diffbot | Allowed | Rules for all crawlers (*) | 0 | 0 |
| ContextFetchBot (us) | ContextFetch | Allowed | Rules for all crawlers (*) | 0 | 0 |
Its homepage in tokens
https://www.cancer.gov/, fetched once and converted locally with the ContextFetch engine. Tokens are characters divided by four, rounded up, the count the API reports in its X-Raw-Tokens and X-Output-Tokens headers.
| Group | Raw HTML | Markdown | Pruned |
|---|---|---|---|
| Tokens | 10,592 | 448 | 55 |
Read cancer.gov through ContextFetch
GET /r/ returns a page as Markdown, with X-Raw-Tokens and X-Output-Tokens headers. Add ?q= and a question to get only the passages that answer it. No key needed for 25 requests a day; a free key has 2,500 credits.
curl -si "https://api.contextfetch.dev/r/https://cancer.gov/"curl -X POST https://api.contextfetch.dev/v1/keys/freeHow ContextFetchBot behaves · All sites and the method · Raw data
Give your agent the web
Your free key comes with 2,500 credits, no signup. One credit reads one page.