Chinese Users Unable to Access Ad‑Blocking Extensions on Firefox Add‑ons Store
A recent report shows that mainland Chinese users receive a regional restriction message and HTTP 451 error when trying to access four popular ad‑blocking extensions on the Firefox Add‑ons website, likely due to legal constraints stemming from past lawsuits against Mozilla's Chinese subsidiary.
Recently, a user on the official Mozilla forum reported that when accessing the pages of ad‑blocking extensions such as uBlock Origin, AdGuard AdBlocker, AdBlock for Firefox, and AdNauseam from a mainland China IP address, a notice appears stating "This page is not available in your region."
Testing confirmed that these four extension pages indeed display the restriction message, preventing Chinese users from installing them via the Firefox Add‑ons store.
Further analysis revealed that the website returns an HTTP 451 error code, which typically signifies that the content is unavailable for legal reasons.
Historically, in 2017 and 2018, Beijing Moxie Firefox Information Technology Co., Ltd. (Mozilla's wholly‑owned subsidiary in China) faced lawsuits from several domestic companies over ad‑blocking features; the judgment took effect in 2019. It remains unclear whether the current blockage is related to those legal cases, and Mozilla has not yet responded on its official forum.
Only the four extensions mentioned above are affected; other ad‑blocking plugins such as Adblock Plus and Ghostery are currently not impacted, and all other types of extensions remain accessible and installable.
Because all Firefox versions share the same addons.mozilla.org page, both the domestic and international editions of Firefox are subject to this restriction.
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