What is MJ12bot? Majestic's SEO crawler
MJ12bot is the crawler of Majestic, a UK search engine run by Majestic-12 Ltd. It maps the links between websites for Majestic's Site Explorer backlink index.
107 of the 1664 major websites we measure block MJ12bot in robots.txt (6%). 91 of those sites name it directly in their robots.txt; the rest are covered by a wildcard rule.
Key facts
| Fact | Detail |
|---|---|
| Operator | Majestic |
| Used for | Majestic's backlink index |
| Type | SEO tool. Collects web data for an SEO tool. Listed here because people look it up beside AI crawlers. It isn't counted in the AI crawler figures. |
| robots.txt token | MJ12bot |
| Operator's documentation | Read it here |
What blocking MJ12bot does
Majestic says MJ12bot follows robots.txt and supports a Crawl-Delay of up to 20 seconds, and that a group naming MJ12bot takes precedence over the wildcard group.
How to allow or block MJ12bot
Add one of these groups to the robots.txt file at the root of your domain. It is a stated preference that well-behaved crawlers read, not an enforcement mechanism.
User-agent: MJ12bot Disallow: /
User-agent: MJ12bot Allow: /
MJ12bot user agent string
Majestic's page doesn't list a full string, so look for MJ12bot in the user agent field of your logs.
How to verify a request is really MJ12bot
Anyone can put a crawler's name in a user agent string, so the name alone proves nothing. We did not find a published IP list or reverse DNS rule from Majestic.
How to whitelist MJ12bot in a firewall or CDN
robots.txt only states a preference. A firewall, CDN or bot protection service can still refuse the request, and the crawler then gets an error even though robots.txt allows it.
- Check that no group in your robots.txt blocks it, using the rule above.
- Add an allow rule in your firewall or CDN that matches the name in the user agent. Keep the rule narrow, because anyone can copy a name.
- Check your server logs for a 200 response from MJ12bot afterwards.
On Cloudflare, also check AI Crawler and Agent access policies, which can block search, agent and training traffic across a site.
Why MJ12bot gets a 403 or 405 error
A 403 means the server refused the request, which usually points to a firewall or bot rule. A 405 means the server refused the request's method, so check any rule that only permits certain methods. A crawler that obeys robots.txt won't request a page it is told to avoid, so an error in your logs points to your server's configuration. To stop it deliberately at the server, this nginx rule returns a 403:
if ($http_user_agent ~* "MJ12bot") {
return 403;
}Who blocks MJ12bot, by sector
| Sector | Sites measured | Blocking | Share |
|---|---|---|---|
| News publishers | 182 | 25 | 14% |
| Social and media platforms | 115 | 14 | 12% |
| Reference and research | 114 | 12 | 11% |
| Technology media | 126 | 14 | 11% |
| AI companies | 128 | 7 | 5% |
| E-commerce and retail | 92 | 5 | 5% |
| Finance and business media | 94 | 5 | 5% |
| Government and institutions | 98 | 5 | 5% |
| Hosting and infrastructure | 98 | 4 | 4% |
| Developer references | 160 | 4 | 3% |
| SaaS platforms | 196 | 6 | 3% |
| Health publishers | 89 | 2 | 2% |
| SEO and marketing tools | 86 | 2 | 2% |
| Travel | 86 | 2 | 2% |
Sites blocking MJ12bot
20minutes.fr, academia.edu, afterpay.com, arm.com, azcentral.com, barrons.com, bestbuy.com, bhf.org.uk, bild.de, biorxiv.org, bloomberg.com, breakingnews.ie, bundesregierung.de, camelcamelcamel.com, cio.com, cmake.org, computerbase.de, consilium.europa.eu, csail.mit.edu, devclass.com, digicert.com, disneyplus.com, distill.pub, dw.com, elmundo.es, elpais.com, eluniversal.com.mx, etymonline.com, facebook.com, figma.com, flickr.com, foodnetwork.com, fortinet.com, france24.com, freshbooks.com, gandi.net, genbeta.com, gnu.org, golem.de, gsmarena.com, guru3d.com, hackernoon.com, illinois.gov, imdb.com, influxdata.com, instacart.com, instagram.com, irishexaminer.com, issuu.com, lastampa.it, linguee.com, lobste.rs, magento.com, marketwatch.com, meta.ai, metacritic.com, midjourney.com, milenio.com, name.com, netflix.com, and 47 more in the full dataset.
Sites that allow MJ12bot by name
androidauthority.com, apollo.io, bleepingcomputer.com, boingboing.net, eff.org, fentybeauty.com, freebsd.org, intel.com, majestic.com, nationalrail.co.uk, pinterest.com, reuters.com, rightmove.co.uk, rosettacode.org, slate.com, soundguys.com, unsplash.com, zeit.de.
See all 36 AI crawlers, the rule change log or the full study. Being reachable is only the first step: how AI search engines choose what to cite covers the rest.
Cite this data
You are welcome to quote or republish these figures. Please credit IndexHalo with a link to this page (CC BY 4.0). All our datasets are on the data page.
IndexHalo. "MJ12bot block rate across major websites." Measured 12 November 2026. https://www.indexhalo.com/ai-crawlers/mj12bot/
<a href="https://www.indexhalo.com/ai-crawlers/mj12bot/">MJ12bot block rate across major websites, IndexHalo</a>