Who blocks AI · #581 in the Majestic Million

robots.txt · checked 9 Nov 2026

Does nejm.org block AI crawlers?

Yes. nejm.org’s robots.txt blocks 5 of the 19 AI crawlers we track, including GPTBot, Google-Extended, PerplexityBot and 2 more. Search engines such as Googlebot and Bingbot may crawl it.

GPTBotBlocked OAI-SearchBotAllowed ClaudeBotAllowed PerplexityBotBlocked Google-ExtendedBlocked CCBotBlocked

robots.txt: www.nejm.org/robots.txt · 82 lines
llms.txt: none
Checked: 9 November 2026, as canaicrawl. We check again every week.

Every bot, and the line that decides

Search engines

Bot	Operator	robots.txt	Deciding line
`Googlebot`	Google	Partly blocked	line 31 · `Disallow: /action` line 32 · `Disallow: /help` and 10 more
`Bingbot`	Microsoft	Allowed	no rule matches the home page
`DuckDuckBot`	DuckDuckGo	Allowed	no rule matches the home page
`Applebot`	Apple	Partly blocked	line 31 · `Disallow: /action` line 32 · `Disallow: /help` and 10 more
`PetalBot`	Huawei	Allowed	no rule matches the home page
`YandexBot`	Yandex	Allowed	no rule matches the home page
`Baiduspider`	Baidu	Allowed	no rule matches the home page

AI search

Bot	Operator	robots.txt	Deciding line
`OAI-SearchBot`	OpenAI	Allowed	no rule matches the home page
`PerplexityBot`	Perplexity	Blocked	line 65 · `Disallow: /` under `User-agent: PerplexityBot`
`Claude-SearchBot`	Anthropic	Allowed	no rule matches the home page
`DuckAssistBot`	DuckDuckGo	Allowed	no rule matches the home page
`Amazonbot`	Amazon	Allowed	no rule matches the home page
`YouBot`	You.com	Allowed	no rule matches the home page

AI training

Bot	Operator	robots.txt	Deciding line
`GPTBot`	OpenAI	Blocked	line 53 · `Disallow: /` under `User-agent: GPTBot`
`ClaudeBot`	Anthropic	Allowed	no rule matches the home page
`Google-Extended`	Google	Blocked	line 62 · `Disallow: /` under `User-agent: Google-Extended`
`CCBot`	Common Crawl	Blocked	line 59 · `Disallow: /` under `User-agent: CCBot`
`Applebot-Extended`	Apple	Allowed	no rule matches the home page
`GoogleOther`	Google	Allowed	no rule matches the home page
`Meta-ExternalAgent`	Meta	Allowed	no rule matches the home page
`Bytespider`	ByteDance	Allowed	no rule matches the home page

User-triggered fetchers

Bot	Operator	robots.txt	Deciding line
`ChatGPT-User`	OpenAI	Blocked	line 56 · `Disallow: /` under `User-agent: ChatGPT-User`
`Claude-User`	Anthropic	Allowed	no rule matches the home page
`Perplexity-User`	Perplexity	Allowed	no rule matches the home page
`MistralAI-User`	Mistral	Allowed	no rule matches the home page
`Meta-ExternalFetcher`	Meta	Allowed	no rule matches the home page

SEO tools

Bot	Operator	robots.txt	Deciding line
`AhrefsBot`	Ahrefs	Blocked	line 71 · `Disallow: /` under `User-agent: AhrefsBot`
`SemrushBot`	Semrush	Blocked	line 80 · `Disallow: /` under `User-agent: SemrushBot`
`MJ12bot`	Majestic	Allowed	no rule matches the home page
`DotBot`	Moz	Allowed	no rule matches the home page

View www.nejm.org/robots.txt · 82 lines

1Sitemap: https://www.nejm.org/sitemap-index-1.txt

2User-agent: *

3Disallow: /action

4Disallow: /help

5Disallow: /search

6Disallow: /feedback

7Disallow: /rss

8Disallow: /action/clickThrough

9Disallow: /action/showLogin

10Disallow: /page/account-confirmation-thanks

11Disallow: /media

12Disallow: /servlet/linkout

13Disallow: /author/

14Disallow: /doi/mlt/

15Allow: /action/showJournal

16Allow: /action/showPublications

17Allow: /action/showXml

18Allow: /media-center/

19Allow: /series

20Allow: /isbn

21Allow: /doi/book

23User-agent: Sosospider

24Disallow: /

26User-agent: AdsBot-Google

27User-agent: AdsBot-Google-Mobile

28Allow: /

30User-agent: Googlebot

31Disallow: /action

32Disallow: /help

33Disallow: /search

34Disallow: /feedback

35Disallow: /rss

36Disallow: /action/clickThrough

37Disallow: /action/showLogin

38Disallow: /page/account-confirmation-thanks

39Disallow: /media

40Disallow: /servlet/linkout

41Disallow: /author

42Disallow: /doi/mlt/

43Allow: /action/showJournal

44Allow: /action/showPublications

45Allow: /action/showXml

46Allow: /media-center/

47Allow: /series

48Allow: /isbn

49Allow: /doi/book

50Allow: /action/sso

52User-agent: GPTBot

53Disallow: /

55User-agent: ChatGPT-User

56Disallow: /

58User-agent: CCBot

59Disallow: /

61User-agent: Google-Extended

62Disallow: /

64User-agent: PerplexityBot

65Disallow: /

67User-agent: SemanticScholarBot

68Disallow: /

70User-agent: AhrefsBot

71Disallow: /

73User-agent: BLEXBot

74Disallow: /

76User-agent: DataForSeoBot

77Disallow: /

79User-agent: SemrushBot

80Disallow: /

What do the bots actually get?

This page reads robots.txt, which states what nejm.org asks of crawlers. A firewall or CDN can still refuse a bot that robots.txt allows. The live check requests the page as each bot and shows the status it gets.

Run a live check on nejm.org Test a path in the robots.txt tester

History

19 October 2026: first checked.

Questions

Does nejm.org block GPTBot?

Yes. nejm.org’s robots.txt disallows GPTBot from the whole site (line 53: Disallow: /). GPTBot is OpenAI’s crawler for training data; blocking it doesn’t affect ChatGPT search, which uses OAI-SearchBot. Checked 9 November 2026.

Does nejm.org block ClaudeBot?

No. nejm.org’s robots.txt lets ClaudeBot crawl the site. ClaudeBot is Anthropic’s crawler for training data. Checked 9 November 2026.

Does nejm.org block Google-Extended?

Yes. nejm.org’s robots.txt disallows Google-Extended from the whole site (line 62: Disallow: /). Google-Extended is the token that controls whether Google may use pages for Gemini training and grounding; it doesn’t affect Google Search. Checked 9 November 2026.

Does nejm.org block PerplexityBot?

Yes. nejm.org’s robots.txt disallows PerplexityBot from the whole site (line 65: Disallow: /). PerplexityBot is the crawler that indexes pages for Perplexity’s answers. Checked 9 November 2026.

Can ChatGPT search find nejm.org?

Yes. nejm.org’s robots.txt lets OAI-SearchBot crawl the site. OAI-SearchBot is the crawler behind ChatGPT search; blocking it keeps the site out of ChatGPT’s search answers. Checked 9 November 2026.