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Ad-filtering Firefox add-ons (uBlock Origin, AdBlock, etc.) are blocked in China on addons.mozilla.org
Firefox starts blocking uBlock Origin and other ad-blocking add-ons in China on addons.mozilla.org ?
Recently , some users reported that uBlock Origin , AdGuard AdBlocker , AdBlock For Firefox , and AdNauseam  were restricted from being accessed by users in mainland China.
When users in mainland China try to access the above ad-filtering add-ons on addons.mozilla.org, the website returns 451 Unavailable For Legal Reasons instead of the normal 200 OK response, and the body of the page states "This page is not available in your region".
The facts can be validated by reproducing the test results below.
By the way, this has nothing to do with China's "great firewall". This action of blocking was performed by Firefox in China. Firefox in China has a long history of arbitrarily blocking websites even for non-political or legal reasons and was found guilty by the Court in China back in 2018 for several such cases.
Sources and evidences:  According to Blocky's test logs, restricted access initially began no earlier than March 8, 2022 and no later than March 19, 2022. Users report: https://bgme.me/@bgme/107986773834355287
The same testing results can be reproduced by testing the below URLs from a China mainland IP address or blocky.greatfire.org which uses multiple China mainland IP addresses in different cities.
Affected add-ons:  https://addons.mozilla.org/zh-CN/firefox/addon/ublock-origin/  https://addons.mozilla.org/zh-CN/firefox/addon/adguard-adblocker/  https://addons.mozilla.org/zh-CN/firefox/addon/adblock-for-firefox/  https://addons.mozilla.org/zh-CN/firefox/addon/adnauseam/
Court cases: （2017）京0101民初4609号 （2018）京73民终433号 （2017）京0101民初4608号 （2018）京73民终397号
All Replies (5)
Note that these add-ons are blocked on the addons.mozilla.org site which returns a 451 error code, so this issue is affecting all Firefox versions, even including Firefox international versions, for users who are accessing addons.mozilla.org from a mainland China IP address.
More user reports:
https://www.v2ex.com/t/841567 (Chinese thread)
https://bgme.me/@bgme/1079867 (Chinese thread)
Okulungisiwe ngu Johnny Yao
I am looking into this matter and will respond soon with a more complete answer.
I've seen on twitter that some chinese ad companies sued Mozilla Online about it and we've - surprisingly - lost.
I am sorry for the delay in responding. I have a response from Mozilla staff:
- Mozilla has geo-restricted certain content blocking add-ons for users in China because adblockers are illegal in China.
- Mozilla did participate in litigation in 2018 arguing for the position that adblockers shouldn't be banned under China’s anticompetition law, but Mozilla lost that litigation.
I hope that this helps clarify matters.
Are adblockers illegal in China? In fact many browsers born in China (mostly based on Chromium and owned by big companies) allow using adblock (some even bundle one), but unfortunately the companies themselves love to inject ads into the browser (for example, the infamous 360 Safe Explorer)
Microsoft Edge, which serves Chinese users as well, didn't set such restrictions.
And what's worse, according to the signing policy of WebExtensions, even sideloading those extensions becomes difficult.
So, it's absolutely an unbelievable faliure on our way to an open Internet - and we can do almost nothing about it.
Okulungisiwe ngu ZeroAurora