01 · Operator
Who operates 404 Checker
- Company
- Drop Web Solutions
- Type
- SEO tool crawler
- Official docs
- 404checker.com
02 · Behavior
What 404 Checker does
All scripts on 404checker.com send the user agent "404 Checker". The tools check HTTP status codes and links on pages users submit. The Link Checker reads robots.txt.
03 · Impact
Why 404 Checker matters for your site
If you allow it
- Triggered by people checking links or status codes
- Light, on-demand traffic
If you block it
- No search visibility
- Anyone can run checks on your site
04 · Allow
How to allow 404 Checker
robots.txt
User-agent: 404 Checker
Allow: /Cloudflare
# Security › WAF › Custom rules › Create rule
Expression: (http.user_agent contains "404 Checker")
Action: Skip › All Super Bot Fight Mode rules
# Also check Security › Bots: "Block AI bots" can block it regardless of robots.txt.WordPress
# WordPress serves a virtual robots.txt. Edit it with your SEO plugin:
# Yoast: SEO › Tools › File editor · Rank Math: General Settings › Edit robots.txt
User-agent: 404 Checker
Allow: /nginx
# nginx serves every user agent by default.
# Make sure no rule like this blocks it:
# if ($http_user_agent ~* "404 Checker") { return 403; }Apache
# Apache serves every user agent by default.
# Make sure .htaccess has no rule like this:
# RewriteCond %{HTTP_USER_AGENT} 404 Checker [NC]
# RewriteRule .* - [F,L]05 · Block
How to block 404 Checker
404 Checker does not always follow robots.txt. Add a server or CDN rule if you need a hard block.
robots.txt
User-agent: 404 Checker
Disallow: /Cloudflare
# Security › WAF › Custom rules › Create rule
Expression: (http.user_agent contains "404 Checker")
Action: BlockWordPress
# WordPress serves a virtual robots.txt. Edit it with your SEO plugin:
# Yoast: SEO › Tools › File editor · Rank Math: General Settings › Edit robots.txt
User-agent: 404 Checker
Disallow: /nginx
# In your server { } block:
if ($http_user_agent ~* "404 Checker") {
return 403;
}Apache
# .htaccess
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteCond %{HTTP_USER_AGENT} 404 Checker [NC]
RewriteRule .* - [F,L]
</IfModule>06 · User agents
User agents we see for 404 Checker
The user agent published by the operator:
404 Checker07 · Verification
Is it really 404 Checker?
404 Checker’s operator publishes no IP ranges or hostnames, so requests cannot be verified. Treat the user agent as a claim, and watch your logs for unusual request rates.
FAQ
Questions about 404 Checker
What is 404 Checker?
It is the user agent of the link and HTTP status tools on 404checker.com.
How do I block 404 Checker?
The site says to add the user agent "404 Checker" to your robots.txt to keep its Link Checker out.
Last reviewed Oct 7, 2026