Yahoo! JAPAN crawler user agent
Operated by Yahoo! JAPAN
Yahoo! JAPAN crawlers use user agents that start with Y!J and collect pages for Yahoo! JAPAN services.
The Yahoo! JAPAN crawler bot at a glance
- Yahoo! JAPAN crawler is operated by Yahoo! JAPAN and crawls web pages for a search engine index.
- The robots.txt token for Yahoo! JAPAN crawler is Y!J.
- Blocking a search engine crawler removes your pages from that search engine's results.
- Yahoo! JAPAN crawler robots.txt support: Not documented.
- Recommendation for Generative Engine Optimization (GEO): Allow.
What is Yahoo! JAPAN crawler?
Yahoo! JAPAN runs several crawlers whose user agents begin with “Y!J”, such as Y!J-ASR.
Yahoo! JAPAN search results are powered by Google, so Googlebot matters most for ranking there.
Should you block Yahoo! JAPAN crawler?
Allow Yahoo! JAPAN crawler unless it causes a measurable load problem.
| Effect on search rankings | Blocking a search engine crawler removes your pages from that search engine's results. |
|---|---|
| Effect on AI visibility | AI features built on that search index, such as Google AI Overviews and AI Mode on top of Googlebot, also lose access to your pages. |
| Follows robots.txt | Not documented |
| Recommendation | Allow |
How to block or allow Yahoo! JAPAN crawler
Put the robots.txt rule in the file at the root of every domain and subdomain, for example https://example.com/robots.txt. The token Y!J is matched case-insensitively. robots.txt alone may not stop Yahoo! JAPAN crawler, so add the Nginx, Apache or Cloudflare rule as well.
robots.txt: block
# Block Yahoo! JAPAN crawler
User-agent: Y!J
Disallow: /robots.txt: allow
# Allow Yahoo! JAPAN crawler
User-agent: Y!J
Allow: /robots.txt: partial
# Keep Yahoo! JAPAN crawler out of private areas only
User-agent: Y!J
Disallow: /wp-admin/
Disallow: /cart/
Disallow: /checkout/
Disallow: /my-account/
Allow: /Nginx
# Nginx: return 403 to Yahoo! JAPAN crawler
if ($http_user_agent ~* "(Y\!J)") {
return 403;
}Apache
# Apache .htaccess: return 403 to Yahoo! JAPAN crawler
RewriteEngine On
RewriteCond %{HTTP_USER_AGENT} (Y\!J) [NC]
RewriteRule .* - [F,L]Cloudflare WAF
# Cloudflare > Security > WAF > Custom rule, action: Block
(http.user_agent contains "Y!J")How to verify real Yahoo! JAPAN crawler traffic
Yahoo! JAPAN publishes no IP list or reverse DNS pattern for Yahoo! JAPAN crawler, so the user agent cannot be verified. Anyone can send the same string. Rate-limit unusual volume instead of trusting the name.
How to find Yahoo! JAPAN crawler in your server logs
Search the web server access log for the token. The command below counts Yahoo! JAPAN crawler requests per URL on Nginx or Apache.
grep -i "Y!J" access.log | awk '{print $7}' | sort | uniq -c | sort -rn | head -20For a full report per AI bot, upload the log to the AI Log File Analyzer, a free tool by Justin Hà.
Yahoo! JAPAN crawler user agent string
The full user agent Yahoo! JAPAN publishes for Yahoo! JAPAN crawler. Version numbers such as Chrome/W.X.Y.Z change over time, so match the token, not the whole string.
Y!J-ASR/0.1 crawler (http://www.yahoo-help.jp/app/answers/detail/p/595/a_id/42716/)Yahoo! JAPAN crawler FAQ
Yahoo! JAPAN crawler identifies itself with the robots.txt token "Y!J". A typical request header reads: Y!J-ASR/0.1 crawler (http://www.yahoo-help.jp/app/answers/detail/p/595/a_id/42716/)
Yahoo! JAPAN has not documented how Yahoo! JAPAN crawler treats robots.txt. Add a robots.txt rule and back it with a server rule if the traffic matters to you.
Blocking a search engine crawler removes your pages from that search engine's results. AI features built on that search index, such as Google AI Overviews and AI Mode on top of Googlebot, also lose access to your pages.
Add two lines to the robots.txt file at the root of each domain and subdomain: "User-agent: Y!J" followed by "Disallow: /". The token is case-insensitive. Changes can take up to 24 hours to be picked up.
Not reliably. Yahoo! JAPAN publishes no IP list or reverse DNS pattern for Yahoo! JAPAN crawler, so anyone can send the same user agent. Rate-limit unusual volume instead of trusting the name.
Search your server access log for "Y!J", for example with: grep -i "Y!J" access.log. The AI Log File Analyzer by Justin Hà counts visits per AI bot from an uploaded log file.
Sources: Public bot registry. Last reviewed by Justin Hà.
See which of these bots actually reach your website
The AI Log File Analyzer by Justin Hà counts visits from GPTBot, ClaudeBot, PerplexityBot and other AI crawlers in your server log, for free. The GEO Technical Package sets up robots.txt, llms.txt and crawler access for AI search.
