Language Reactor for Firefox: What Actually Works Instead
Language Reactor does not have a Firefox version. It was built for Chrome and other Chromium browsers and has stayed there, which is a real problem if Firefox is your daily browser. This page lays out what actually exists for Firefox users in 2026, compares the options honestly — including LangKey — and tells you when staying on Chrome is the better call.
| Feature | LangKey | Language Reactor |
|---|---|---|
| Firefox extension | ||
| Chrome / Edge extension | ||
| Official store listing | Chrome, Edge and Firefox | Chrome Web Store only |
| Dual subtitles on Firefox | ||
| Click-to-translate on Firefox | ||
| Dictation, shadowing, AI conversation | ||
| SRS review and Anki export | Basic saved-items review | |
| Bilibili and TED | ||
| Open source | ||
| Browser you must switch to | None — it works on your browser | Chrome, Edge or another Chromium browser |
Why People Still Look for It on Firefox
- Its Netflix integration and phrase catalog are mature after years of polish — if you already use it on Chrome, nothing about that changes.
- A large community means more third-party tutorials, subtitle packs and forum answers than newer tools have.
- If your study happens entirely in Chrome, it remains a proven free option for Netflix and YouTube dual subtitles.
Why LangKey Works Where Language Reactor Does Not
- A real Firefox build on addons.mozilla.org — not an unofficial port, and not a Chromium wrapper.
- The same feature set across Chrome, Edge and Firefox: dual subtitles, click-to-translate, 7 practice modes and SRS review.
- Bilibili support on Firefox too — useful if you study Mandarin or Japanese through Bilibili and browse with Firefox.
- Free core and open source, with no browser lock-in: switching between Chrome and Firefox does not cost you your vocabulary.
The Verdict
There is no official Language Reactor for Firefox, and none appears to be coming — it was built for Chromium and stays there. If dual subtitles are all you need and you can use Chrome, it is still a fine tool. But if Firefox is your daily browser, you need something built for it. LangKey ships native Firefox support with the same practice modes and vocabulary review it offers on Chrome, costs nothing to start, and lets you keep the browser you already use.
Frequently Asked Questions
Does Language Reactor work on Firefox?
No. Language Reactor is built for Chrome and other Chromium browsers, and it does not ship a Firefox extension. Listings sometimes seen on Firefox Add-ons under that name are unofficial uploads rather than releases from the original developer, and installing one means trusting an unknown party with your browsing data.
What is the best language learning extension for Firefox?
It depends on what you watch. LangKey covers YouTube, Bilibili, TED and Netflix on Firefox with dual subtitles, click-to-translate and 7 practice modes, and the core is free. Trancy also ships an official Firefox extension and leans on AI-generated subtitles. asbplayer is open source and unmatched for local video files and Anki mining, but it expects you to supply your own subtitle files.
Is the LangKey Firefox version missing features compared with Chrome?
No. It is the same extension across Chrome, Edge and Firefox — dual subtitles, word lookup, dictation, shadowing, AI conversation and SRS review all work on Firefox. Vocabulary and progress sync by account, so moving between browsers does not cost you your saved words.
Can I run Language Reactor on Firefox with a workaround?
There is no reliable one. Some Chromium-based browsers can load Chrome extensions, but that depends on several moving parts staying compatible at once and tends to break whenever any of them updates. A native Firefox extension is the stable route.
Do I have to pay for a language learning extension on Firefox?
No. The LangKey core features — bilingual subtitles, click-to-translate, all 7 practice modes and SRS review — are free on Firefox, and the source code is public on GitHub. Several alternatives keep free tiers too, though most reserve word saving or AI features for paying subscribers.