SemrushBot-SI
Semrush operates SemrushBot-SI, the crawler behind its On Page SEO Checker and SEO Content Template reports. It honors robots.txt under the token SemrushBot-SI and accepts a Crawl-delay of at most 1 second. Semrush publishes its addresses in knowledge base prose (85.208.98.53 and 85.208.98.0/24) rather than a machine-readable file, and documents no reverse-DNS suffix.
What SemrushBot-SI does
Semrush does not publish a full user-agent string for this bot, only the token SemrushBot-SI, so that token is what to look for in logs. On the operator's bot page the token appears with two spaces after User-agent:, which looks like a typo. Semrush says the bot crawls sites for the On Page SEO Checker tool and similar tools, producing the On Page SEO Checker and SEO Content Template reports. Those reports are the reason for its visits.
Blocking SemrushBot-SI in robots.txt stops the On Page SEO Checker and SEO Content Template reports from crawling your pages; allowing it lets Semrush users audit your pages with those tools. Two operator notes deserve restating. The On Page SEO Checker crawler only accepts a Crawl-delay of 1 second, and anything above that value makes the crawler ignore the page, so a larger Crawl-delay behaves like a block. Semrush also lets On Page SEO Checker users change the crawling user agent to one it labels 'Google Bot' if Semrush Bot is blocked, so a robots.txt rule on the SemrushBot-SI token alone does not guarantee those reports stop.
Verification is by IP address only. Semrush knowledge base article 375 tells site owners to whitelist 85.208.98.53 and the 85.208.98.0/24 range together with User-agent: SemrushBot-SI, on port 80 for HTTP and port 443 for HTTPS. There is no machine-readable range file and no reverse-DNS suffix in the documentation. The same article quotes an in-product error message naming 'SEMRushBot-Desktop'; that is a label inside the error text, not a documented user-agent token, so do not expect it in logs. JavaScript execution is undocumented.
Operator note. Knowledge Base article 375 states: "On Page SEO Checker crawlers only accept crawl-delay of 1 second. Anything above this value would make the crawler ignore the page." The same article quotes an in-product error message, "SEMRushBot-Desktop couldn't crawl the page because it was blocked by robots.txt"; 'SEMRushBot-Desktop' is only an error-message label there, not a documented user-agent token. Article 564 says On Page SEO Checker lets users "change the user agent that crawls your site" to one "we label as 'Google Bot'" if Semrush Bot is blocked. JavaScript execution is not documented.
Controlling SemrushBot-SI with robots.txt
Use the token SemrushBot-SI in robots.txt. Semrush documents that SemrushBot-SI honors robots.txt directives.
User-agent: SemrushBot-SI
Disallow: /User-agent: SemrushBot-SI
Allow: /Verifying a request is really SemrushBot-SI
Anyone can put SemrushBot-SI in a User-Agent header. Semrush publishes IP addresses in Knowledge Base prose rather than a machine-readable file: article 375 says to "whitelist the following IP addresses and User-agent", listing "85.208.98.53", "85.208.98.0/24" and "User-agent: SemrushBot-SI", on "Port 80: HTTP" and "Port 443: HTTPS". No reverse-DNS suffix is documented.
Common questions
Should I block SemrushBot-SI?
Only if you do not want Semrush users running On Page SEO Checker or SEO Content Template reports against your pages, which is what Semrush says this bot crawls for. It honors robots.txt, so a Disallow for User-agent: SemrushBot-SI works. Note that Semrush allows users to switch the report's user agent if the Semrush bot is blocked.
Does SemrushBot-SI respect Crawl-delay?
Partly. Semrush states that the On Page SEO Checker crawlers only accept a Crawl-delay of 1 second; anything above that value makes the crawler ignore the page. A Crawl-delay of 1 slows it, and a larger value in effect blocks it.
How do I verify SemrushBot-SI?
Match the source IP against the addresses Semrush publishes in its knowledge base: 85.208.98.53 and the 85.208.98.0/24 range, arriving on port 80 or 443. Semrush has no machine-readable IP file and documents no reverse-DNS suffix, so an IP check against that prose is the only operator-backed method.
Sources
Every fact on this page was checked against Semrush's own documentation, listed below, and re-checked by a second reviewer before publication. Reviewed September 2026.
Related crawlers
This registry documents how operators describe their own bots so site owners can identify and control them. It does not publish third-party IP lists or guess at undocumented behaviour. To see how your own site responds to automated visitors, the bot detection scanner reads a URL's live response and names the protection it finds.