YahooCacheSystem
Content fetcher caching web pages and thumbnails for Yahoo
About this crawler
YahooCacheSystem is a web crawler identified by the regular-expression pattern YahooCacheSystem in the User-Agent request header. It is categorised as seo. Use the regex above to detect, log, allow, or block YahooCacheSystem traffic in your web server, CDN edge rules, or robots.txt.
Block-rate · top 25k sites
No block-rate data for this crawler.
Technical details
- Name
- YahooCacheSystem
- Pattern
YahooCacheSystem- Tags
- seo
- Reference
- https://developer.yahoo.com/oauth2/guide/
- Added
- 2026/04/17
- rDNS suffixes
.yahoo.co.jp,.yahoo.com,.yahoo.net- Instances
- 1 known sample(s)
rDNS verification (FCrDNS)
Verify a request is genuinely YahooCacheSystem with forward-confirmed reverse DNS: the client IP's PTR record must end in one of the suffixes below and a forward A/AAAA lookup of that hostname must return the same IP. UA strings alone are spoofable; FCrDNS is not.
.yahoo.co.jp.yahoo.com.yahoo.net
Sample User-Agent strings
YahooCacheSystem; YahooWebServiceClient
Block this crawler
robots.txt — disallow YahooCacheSystem:
User-agent: YahooCacheSystem
Disallow: /
Apache .htaccess — return 403:
RewriteEngine On
RewriteCond %{HTTP_USER_AGENT} YahooCacheSystem [NC]
RewriteRule .* - [F,L]
Nginx — return 403 inside a server block:
if ($http_user_agent ~* "YahooCacheSystem") {
return 403;
}
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