Mozilla-Tabstack: share of top websites blocking it

On 26 October 2026, 4.5% of the readable top 10k websites fully blocked Mozilla-Tabstack in robots.txt (bounds 3.6% to 23.8% over all 8,220 websites, 1,659 of them unreadable); 3.9% blocked it partly and 0.2% named it.

Last verified 2026-10-26 21:13 UTC (daily run of 2026-10-26). Proof for that day.

Operator
Mozilla that performs programmatic, AI-driven interactions with web content through Tabstack
What it is
AI Data Providers
Description
Mozilla-Tabstack is an AI agent operated by Mozilla that performs programmatic, AI-driven interactions with web content through Tabstack. More info can be found at https://knownagents.com/agents/mozilla-tabstack
robots.txt token
User-agent: Mozilla-Tabstack
Listed since
2026-10-26 (in this ledger's registry)

Fully blocks

4.5%

294 sites; bounds 3.6% to 23.8%

Partly blocks

3.9%

258 sites

Name it explicitly

0.2%

16 sites; unreadable: 3,439

Over time

Share of panel sites blocking Mozilla-Tabstack4 lines, 2016-09-05 to 2026-10-26; values between 2.39 and 5.53 %; latest 4.48 %.2.143.053.964.885.79Sep 2016Mar 2019Sep 2021Apr 2024Oct 2026blocks, reconstructed (Common Crawl): 2016-09-05 UTC: 3.14 %blocks, reconstructed (Common Crawl): 2017-09-25 UTC: 3.51 %blocks, reconstructed (Common Crawl): 2018-09-24 UTC: 3.61 %blocks, reconstructed (Common Crawl): 2019-09-23 UTC: 2.80 %blocks, reconstructed (Common Crawl): 2020-09-28 UTC: 2.52 %blocks, reconstructed (Common Crawl): 2021-09-27 UTC: 2.61 %blocks, reconstructed (Common Crawl): 2022-10-03 UTC: 2.55 %blocks, reconstructed (Common Crawl): 2024-09-16 UTC: 2.39 %blocks, reconstructed (Common Crawl): 2026-09-21 UTC: 2.77 %partly blocks, reconstructed (Common Crawl): 2016-09-05 UTC: 5.04 %partly blocks, reconstructed (Common Crawl): 2017-09-25 UTC: 4.91 %partly blocks, reconstructed (Common Crawl): 2018-09-24 UTC: 4.82 %partly blocks, reconstructed (Common Crawl): 2019-09-23 UTC: 4.76 %partly blocks, reconstructed (Common Crawl): 2020-09-28 UTC: 4.82 %partly blocks, reconstructed (Common Crawl): 2021-09-27 UTC: 4.98 %partly blocks, reconstructed (Common Crawl): 2022-10-03 UTC: 4.91 %partly blocks, reconstructed (Common Crawl): 2024-09-16 UTC: 5.10 %partly blocks, reconstructed (Common Crawl): 2026-09-21 UTC: 5.53 %blocks, daily observation: 2026-10-26 UTC: 4.48 %partly blocks, daily observation: 2026-10-26 UTC: 3.93 %

"Partly blocks" counts every robots.txt whose rules for Mozilla-Tabstack disallow some paths, including generic rules for all crawlers (for example /search); it is not a measure of targeted AI policy. Shares are of the readable websites (W − U: 8,220 websites, 1,659 unreadable); the bounds assume none / all of the unreadable sites block. Solid: daily first-party observations (top 10k of the Tranco list W3ZV9, one fixed cohort). Dashed: reconstructed from Common Crawl (top 10k, sites readable in every crawl), a separate series.

Reconstructed values per crawl
CrawlDateBlocksSites read
CC-MAIN-2016-362016-09-053.1%3,216
CC-MAIN-2017-392017-09-253.5%3,216
CC-MAIN-2018-392018-09-243.6%3,216
CC-MAIN-2019-392019-09-232.8%3,216
CC-MAIN-2020-402020-09-282.5%3,216
CC-MAIN-2021-392021-09-272.6%3,216
CC-MAIN-2022-402022-10-032.5%3,216
CC-MAIN-2024-382024-09-162.4%3,216
CC-MAIN-2026-392026-09-212.8%3,216

Recent blockers

Sites that started fully blocking Mozilla-Tabstack since 2026-07-28, highest-ranked first.

DateSiteWhat changed
No changes recorded yet. The first daily run is the baseline; changes appear from the second day on.

Recent unblockers

DateSiteWhat changed
No changes recorded yet. The first daily run is the baseline; changes appear from the second day on.

Sites blocking Mozilla-Tabstack now

facebook.com (*) · fbcdn.net (*) · instagram.com (*) · twitter.com (*) · googlevideo.com (*) · netflix.com (*) · x.com (*) · pinterest.com (*) · baidu.com (*) · reddit.com (*) · skybridge.click (*) · registrar-servers.com (*) · flickr.com (*) · meraki.com (*) · t.co (*) · linktr.ee (*) · imdb.com (*) · reuters.com (*) · demdex.net (*) · weibo.com (*) · naver.com (*) · trustpilot.com (*) · netflix.net (*) · nflxvideo.net (*) · wsj.com (*) · cookiedatabase.org (*) · gcdn.co (*) · kwai.net (*) · edgecdn.ru (*) · sohu.com (*) · threads.com (*) · netcraze.io (*) · sharethrough.com (*) · hstgr.net (*) · lemonde.fr · imgsmail.ru (*) · fb.com (*) · hihonorcloud.com (*) · pinimg.com (*) · quantserve.com (*) · creativecdn.com (*) · crwdcntrl.net (*) · vkontakte.ru (*) · disneyplus.com (*) · sentinelone.net (*) · adform.net (*) · academia.edu (*) · daum.net (*) · tiktokw.us (*) · xiaohongshu.com (*) · mailchi.mp (*) · btloader.com (*) · namecheaphosting.com (*) · jamfcloud.com (*) · rocketmoney.dev (*) · ouest-france.fr (*) · namu.wiki (*) · theconversation.com · fmkorea.com (*) · amap.com (*)

(*) blocked through the * group, not by name. Full list in current.csv.

Cite this

InfraRabbit AI Crawl Ledger, "Share of top websites blocking Mozilla-Tabstack", https://infrarabbit.com/crawlers/bot/Mozilla-Tabstack, retrieved 2026-10-26. CC BY 4.0.