Y!J

search-engine Y!J

Yahoo Japan search engine web crawler bot

About this crawler

Y!J is a web crawler identified by the regular-expression pattern Y!J in the User-Agent request header. It is categorised as search-engine. Use the regex above to detect, log, allow, or block Y!J traffic in your web server, CDN edge rules, or robots.txt.

Block-rate · top 25k sites

0.065%
latest snapshot
2026-06-04
matched key: Y!J
2026-05-012026-06-040.11%

Technical details

Name
Y!J
Pattern
Y!J
Tags
search-engine
Reference
https://www.yahoo-help.jp/app/answers/detail/p/595/a_id/42716/~/%E3%82%A6%E3%82%A7%E3%83%96%E3%83%9A%E3%83%BC%E3%82%B8%E3%81%AB%E3%82%A2%E3%82%AF%E3%82%BB%E3%82%B9%E3%81%99%E3%82%8B%E3%82%B7%E3%82%B9%E3%83%86%E3%83%A0%E3%81%AE%E3%83%A6%E3%83%BC%E3%82%B6%E3%83%BC%E3%82%A8%E3%83%BC%E3%82%B8%E3%82%A7%E3%83%B3%E3%83%88%E3%81%AB%E3%81%A4%E3%81%84%E3%81%A6
Added
2015/05/26
rDNS suffixes
.yahoo.co.jp, .yahoo.com, .yahoo.net
Instances
6 known sample(s)

rDNS verification (FCrDNS)

Verify a request is genuinely Y!J 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.

Sample User-Agent strings

Y!J-ASR/0.1 crawler (http://www.yahoo-help.jp/app/answers/detail/p/595/a_id/42716/)
Y!J-BRJ/YATS crawler (http://help.yahoo.co.jp/help/jp/search/indexing/indexing-15.html)
Y!J-PSC/1.0 crawler (http://help.yahoo.co.jp/help/jp/search/indexing/indexing-15.html)
Y!J-BRW/1.0 crawler (http://help.yahoo.co.jp/help/jp/search/indexing/indexing-15.html)
Mozilla/5.0 (iPhone; Y!J-BRY/YATSH crawler; http://help.yahoo.co.jp/help/jp/search/indexing/indexing-15.html)
Mozilla/5.0 (compatible; Y!J SearchMonkey/1.0 (Y!J-AGENT; http://help.yahoo.co.jp/help/jp/search/indexing/indexing-15.html))

Block this crawler

robots.txt — disallow Y!J:

User-agent: Y!J Disallow: /

Apache .htaccess — return 403:

RewriteEngine On RewriteCond %{HTTP_USER_AGENT} Y!J [NC] RewriteRule .* - [F,L]

Nginx — return 403 inside a server block:

if ($http_user_agent ~* "Y!J") { return 403; }
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