Safe Official docs Data Scrapers

yacy

Operated by YaCy Community

Quick Facts

User-Agent:
yacy
Category:
Data Scrapers
Operator:
YaCy Community
Safety:
Safe
Blocking Impact:
Low - No SEO ranking impact
SEO Impact Score:
2/10
Official docs:
yacy.net

Confirmed by the operator

YaCy Community names yacy on its own documentation page, linked above. The token, purpose and robots.txt behaviour on this profile come from that page, re-checked on October 19, 2026.

What is yacy?

YaCy is a distributed, peer-to-peer search engine. Users run their own crawler nodes.

YaCy is a distributed, peer-to-peer search engine. Users run their own crawler nodes.
yacy is a data aggregation crawler. Unlike search bots or AI crawlers, its purpose is typically to collect content for private datasets, price monitoring, or research. Blocking yacy via robots.txt or at the server level has NO negative SEO impact. If you see excessive crawl volume from this bot in your logs, a hard block is recommended.

What happens if you block yacy?

✅ Minimal Impact - Blocking yacy has no meaningful effect on your search engine rankings or organic traffic.
Generally safe to allow; provides legitimate crawling value.

How to block yacy with robots.txt

<code>User-agent: yacy</code> - Matching is case-insensitive. Robots.txt is fetched from the root of each subdomain separately.

Block completely (robots.txt)
User-agent: yacy Disallow: /
Allow all (robots.txt)
User-agent: yacy Allow: /
Block private only (robots.txt)
User-agent: yacy Disallow: /private/ Disallow: /api/ Disallow: /admin/ Allow: /
Nginx server block
# Nginx: Hard-block yacy if ($http_user_agent ~* "yacy") { return 403 "Bot blocked"; }
Apache .htaccess
# Apache: Hard-block yacy SetEnvIfNoCase User-Agent "yacy" bad_bot Order Allow,Deny Allow from all Deny from env=bad_bot
Meta robots tag
<meta name="robots" content="noindex, nofollow">
X-Robots-Tag header
X-Robots-Tag: noindex, nofollow

Is yacy safe to allow?

Yes, yacy is a safe and legitimate crawler. It is operated by YaCy Community, which publicly documents its crawler at an official URL and follows the Robots Exclusion Protocol (RFC 9309). The user-agent string yacy is verifiable via reverse-DNS lookup on the crawling IP addresses. You can safely allow it unless you have a specific reason to block (e.g., AI training opt-out or SEO tool visibility).
Verify by reverse-DNS lookup: legitimate yacy requests resolve to yacy-community's domain.

What does yacy do?

Understanding yacy's purpose helps you decide whether to allow or block it.

  • Extracts content, prices, or data from websites
  • May be used for competitive intelligence
  • Often operates without explicit permission
  • Can increase server load and bandwidth usage
  • May violate terms of service or copyright

yacy in context

yacy is a retrieval crawler that feeds AI search answers operated by YaCy Community. In plain terms, it builds a search or answer index. Our database files it under data scrapers and ranks it Tier 6, the lowest priority: scrapers and tools that offer most sites little or nothing. 37 of the 39 data scrapers in our database share this tier.

Its safety rating is safe and its blocking impact is low. So the decision about yacy rests on what you want from YaCy Community, not on its behaviour. How we rate safety and impact.

How site owners treat yacy

Our robots.txt study of the Tranco top 10,000 did not track yacy as a named token, so we do not publish an adoption figure for it. If you run a large site, your own logs are the best evidence of how often it visits.

Does it follow robots.txt?

yacy's operator does not clearly document how it treats robots.txt. Write the yacy rule anyway, then confirm in your logs that its requests stop.

YaCy Community crawlers and close alternatives

yacy is one of 2 YaCy Community crawlers in our database. A User-agent: yacy group controls yacy only; the other YaCy Community tokens below need their own lines.

  • yacy: this crawler (Tier 6)
  • yacybot: yacybot, builds a search or answer index (Tier 6)

To give yacy the same answer as its siblings, stack User-agent: yacy with their lines above one set of rules; to treat yacy differently, give it its own group.

No other crawler in our data scrapers category has exactly the same purpose, which makes yacy an unusual case: decide about it on its own merits.

We first recorded yacy on March 17, 2026. YaCy Community documents it on yacy.net, and we recheck that page before each release.

Which rule yacy actually follows

yacy reads exactly one group in robots.txt, the most specific one that names yacy, and never combines rules across groups. This short file shows the trap:

User-agent: *
Disallow: /private/

User-agent: yacy
Disallow: /drafts/
  1. Find the group. yacy looks for a group naming yacy. One exists, so it ignores User-agent: * completely.
  2. Apply only that group. It is refused /drafts/ and nothing else.
  3. The surprise. /private/ is open to yacy, because that rule lives in the * group it no longer reads. To keep it out of both, repeat Disallow: /private/ inside its own group.
Test yourself: does a rule under User-agent: * apply to yacy if the file also has a User-agent: yacy group?

No. Once a group names it, yacy reads only that group. Put every rule you want it to follow inside its own group.

Test yourself: will blocking yacy remove your pages from AI answers?

Often, yes. yacy is a retrieval crawler that feeds AI search answers, so pages it cannot fetch can drop out of the answers or results it supports.

Test yourself: is User-agent: yacy the same as User-agent: yacy?

Yes. RFC 9309 makes user-agent matching case-insensitive. Paths are a different story: Disallow: /Blog/ does not block /blog/.

Should you allow yacy? Decide by situation

Recommended setting for yacy by type of site
If you are...Recommended setting
You publish content and want AI answers to cite itAllow it. yacy fetches pages for answers, so blocking it can remove you from them.
You license content and want to stop AI trainingBlocking it does not stop training, because yacy is a retrieval crawler that feeds AI search answers. Block the operator's training crawler instead.
You run an online shopAllow it on product and category pages, which are the pages shoppers ask assistants about.
Your server is under load from botsRate-limit before blocking. It is rated safe in our database.

Check yacy on your own site

  1. Open /robots.txt on your domain and search for yacy. If it is not named, it follows User-agent: *.
  2. List the Disallow lines in the group yacy follows and test your key URLs against them; the longest match wins, and Allow wins a tie.
  3. Look beyond the file. A firewall or bot manager can refuse yacy even when robots.txt allows it, and that never shows in the file.
  4. Run our AI crawlability test to see how yacy and every other crawler we track are treated in one pass, including firewall refusals.

Common mistakes with yacy

The errors we see most often with yacy in the files and firewalls we test:

  1. Blocking yacy while trying to stop AI training. Retrieval crawlers fetch pages so answers can cite them; blocking it can remove you from those answers without affecting training.
  2. Letting a firewall or bot-fight mode refuse yacy while robots.txt allows it. The file looks right, but the crawler still gets a 403 or a challenge page.
  3. Forgetting that once a User-agent: yacy group exists, yacy ignores every rule under User-agent: *.

All three hide inside a file that looks correct, so check yacy from outside after every change.

Spotting yacy in your logs

robots.txt says what yacy may do; your access logs show what it actually did.

Count requests

On a server with standard Nginx or Apache logs, this counts matching requests per day (adjust the log path for your host):

grep -iE "yacy" /var/log/nginx/access.log \
  | awk '{print $4}' | cut -d: -f1 | sort | uniq -c

And this shows which paths it requested most, which is the quickest way to see whether your Disallow lines are being respected:

grep -iE "yacy" /var/log/nginx/access.log \
  | awk '{print $7}' | sort | uniq -c | sort -rn | head -20

Check the requests are genuine

Anyone can send the yacy user-agent, so confirm the source before acting on a match:

  • yacy: we hold no published IP list, so use reverse DNS where the operator documents a hostname and treat an unverifiable yacy request with caution.

Frequently Asked Questions

What is the official user-agent string for yacy?
The official user-agent string for yacy is: yacy. This is the exact string you must use in robots.txt, Nginx, Apache, or Cloudflare firewall rules to target this bot. User-agent matching in robots.txt is case-insensitive, but the string must be spelled correctly. You can verify that a request genuinely comes from yacy by performing a reverse-DNS lookup on the source IP - legitimate bots resolve back to their operator's domain.
Is yacy safe?
Yes, yacy is a safe and legitimate crawler. It is operated by YaCy Community, which publicly documents its crawler at an official URL and follows the Robots Exclusion Protocol (RFC 9309). The user-agent string yacy is verifiable via reverse-DNS lookup on the crawling IP addresses. You can safely allow it unless you have a specific reason to block (e.g., AI training opt-out or SEO tool visibility).
Will blocking yacy hurt my SEO?
✅ Minimal Impact - Blocking yacy has no meaningful effect on your search engine rankings or organic traffic.
How do I block yacy in robots.txt?
Add the following lines to your /robots.txt file:
User-agent: yacy
Disallow: /

This instructs yacy not to crawl any path on your site. The Disallow: / directive covers the entire domain including subfolders. To only block specific sections, replace / with the path (e.g., Disallow: /blog/). Note: robots.txt is publicly readable - any bot or human can inspect it at yourdomain.com/robots.txt.
Does yacy respect robots.txt?
Yes - yacy is a well-behaved bot operated by YaCy Community. It fetches and parses /robots.txt before crawling any page, following RFC 9309.
How do I verify if yacy is crawling my site?
Search your web server access logs for the string yacy (case-insensitive grep: grep -i "yacy" /var/log/nginx/access.log). You can also check Google Search Console → Coverage → Crawl Stats for Googlebot variants. For yacy specifically, filter by user-agent in your log analysis tool (GoAccess, AWStats, etc.).
What is the crawl frequency of yacy?
yacy crawls at a moderate rate. If you notice excessive traffic in your logs, you can add a Crawl-delay directive: 
User-agent: yacy
Crawl-delay: 10
(10 second delay between requests).
Can I block yacy from specific pages only?
Yes. Instead of a global Disallow: / you can restrict yacy to specific paths:
User-agent: yacy
Disallow: /private/
Disallow: /staging/
Allow: /

This allows yacy everywhere except the listed paths. Path matching in robots.txt uses prefix matching - Disallow: /private/ blocks /private/page.html but NOT /public/private/.
Is yacy causing high server load?
If yacy is generating excessive requests, you can:
1. Add Crawl-delay: 30 below the User-agent directive in robots.txt.
2. Rate-limit the user-agent via Nginx's limit_req_zone or Apache's mod_ratelimit.
3. Block it outright at Cloudflare WAF with rule: http.user_agent contains "yacy".
4. Use fail2ban to auto-block IPs exceeding request thresholds.

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