Language Reactor for iPhone: What Actually Works

You use Language Reactor on your laptop, you get used to having two subtitle lines, and then you try to take it with you. You search the App Store for "Language Reactor" and get a row of results whose names start with exactly those words — and not one of them is made by the people who make Language Reactor.

So here is the honest version. There is no official Language Reactor app for iPhone or iPad. There is no Safari extension either. What there is instead is one workable route for YouTube, one problem nobody can solve on a phone, and a popular Android workaround that quietly died in early 2025.

Full disclosure before we go further: we make Linglass, which does some of what Language Reactor does and has an iPhone app. We are not affiliated with Language Reactor, and we'll be specific below about the parts we don't cover.

The short answer

One sentence if you remember nothing else: on a phone, YouTube is solvable and Netflix is not — and the reason is the video player, not the browser.

Is there an official Language Reactor iOS app?

No. Language Reactor is distributed as a browser extension through the Chrome Web Store, which also covers Edge. Its own help pages point you there, and its FAQ answers the platform question directly — asked whether it supports "Disney+/Amazon Prime/Android/etc.", the answer is that these platforms aren't supported yet and might be in future. iOS isn't listed at all.

What you find in the App Store instead is a cluster of apps whose display names begin with "Language Reactor" followed by another word. They are separate products from separate developers. Some are decent, some are thin, but none of them is the extension you use on your laptop, and installing one won't give you your saved words or your settings.

This is worth knowing before you pay for anything: an App Store name is a marketing surface, and a familiar name in it doesn't mean a familiar product behind it. Judge these apps — ours included — on what they actually play and what they actually do with the subtitles, not on the name.

Why there isn't one — and why the usual explanation is wrong

The reason you'll see repeated is that Safari on iPhone doesn't allow extensions to inject scripts. That's not true, and it matters, because the real reason is more interesting.

Safari has supported web extensions on iPhone and iPad since iOS 15, in 2021. They're built by developers, shipped through the App Store, and switched on in Safari's settings. So an iOS extension is technically buildable. Language Reactor simply hasn't built one — its extension exists in the Chrome format, and porting it means shipping and maintaining a second product on a platform where the two big use cases behave very differently.

Those two use cases are the actual story:

• YouTube plays in mobile Safari. A page exists, subtitle tracks exist, and something can in principle attach to them.
• Netflix does not play in mobile Safari on an iPhone at all. Open netflix.com on a phone and you get a "Get the App" page instead of a player. There is no web player, so there is nothing for any extension to attach to — not Language Reactor's, not ours, not anyone's.

That single fact is why every honest page ends up at the same conclusion. Netflix dual subtitles on an iPhone aren't blocked by a policy that might change next year; there is no browser video to work with in the first place.

What actually works on iPhone: YouTube, in an app that owns the player

Since the extension route is closed, the working answer on iOS is an app that plays the video itself and draws both subtitle lines over its own player. That's what the Linglass iPhone app does.

You paste a YouTube link or pick something from the built-in catalog, the video plays inside the app, and you get the original subtitle line with your native language underneath — the same two-line arrangement you're used to on a laptop. Tap any word and you get its translation in the context of that sentence, plus pronunciation. Save it and it goes into a spaced-repetition deck you review later.

Two things that come up often, answered honestly:

• Videos with no subtitles at all still work. If a video ships no caption track, the app transcribes the audio and translates it, which is the case Language Reactor can't help with either. On the free plan this is capped by video length rather than switched off.
• The free plan is a real one. Fifteen contextual translations a day, unlimited saved words, unlimited review, and pronunciation on every word — with no trial clock.

And the parts we don't cover, stated plainly: no Netflix on mobile (see above — nobody has it), no Android app yet, and the app is built for iPhone. It installs and runs on an iPad, but it isn't a tablet-optimised layout.

The iPad is a genuinely different case

People assume an iPad behaves like a laptop, and for once that's half right.

Safari on iPadOS is desktop-class: netflix.com does play in the browser on an iPad, unlike on an iPhone. So the structural blocker above doesn't apply there — an iPad running Safari has a real Netflix web player on screen.

What's missing on iPad is the other half: there is no Safari extension for dual subtitles to install. Language Reactor ships Chrome-only, and neither we nor the other tools in this category have shipped a Safari build. So the iPad ends up in an odd position — the only mobile device where Netflix dual subtitles are theoretically reachable, and still nowhere to get them today. For YouTube on an iPad, the app route works fine.

Android: the workaround everyone recommends is dead

If you've searched this before, you've seen the advice: install Kiwi Browser on Android, add Language Reactor from the Chrome Web Store, done. That advice is now stale.

Kiwi Browser was discontinued in January 2025 — its repository was archived and it left the Play Store. Its extension code was contributed to Microsoft Edge, and Edge's Android Canary build can run Chrome extensions, but it's a developer preview, installation means handling extension files by hand, and stability with any given extension is not guaranteed.

Chrome for Android has never had an extension engine at all, and that hasn't changed. Firefox for Android runs a limited approved add-on list, which is the one supported extension-like route left. If you want something reliable on Android right now, the honest answer is a computer — and, in our case, an Android app that isn't out yet.

What about Disney+, Prime Video, Crunchyroll?

Nowhere, on any device, from any of these tools — including on desktop. Language Reactor's FAQ says as much for Disney+ and Prime. We support YouTube, Netflix, iQIYI and Viki in the browser extension, and YouTube in the phone app. Anyone promising dual subtitles on Prime Video on a phone is describing something that doesn't exist.

If you already use Language Reactor on a computer

You don't have to choose sides. A sensible split is: keep whatever you like on your laptop, and put a phone app on the phone, because those are two different problems and no tool spans both.

If you want the phone half to feed the same vocabulary as the computer half, that only happens inside one product — one account, one deck. That's the case for using the same tool in both places, and it's why the pairing we'd suggest is our browser extension on the computer — which does cover Netflix, iQIYI and Viki — plus the iPhone app for everything you watch away from a desk. If you'd rather compare the two tools feature by feature first, we wrote that comparison and a wider list of alternatives.

Getting started on your phone

1. Install the app on your iPhone. It needs iOS 16.4 or later.
2. Create a free account, then pick two languages — the one you're learning and your native one.
3. Paste a YouTube link, or open a video from the built-in catalogue of scored, level-tagged channels.
4. Both subtitle lines appear over the player. Tap a word for its translation in context; save it to review later.

Frequently asked questions

Is there a Language Reactor app for iPhone?

No. Language Reactor is a browser extension distributed through the Chrome Web Store and it runs on desktop Chrome or Edge. There is no official iOS app and no Safari extension. The App Store results whose names start with "Language Reactor" are separate products from other developers, not the extension you use on a computer.

Can I use Language Reactor on Safari?

No. Safari has supported web extensions on iPhone, iPad and Mac since iOS 15, so the platform allows it, but Language Reactor has only ever shipped in the Chrome extension format. Nobody in this category has released a Safari build yet.

Can I get dual subtitles on Netflix on my iPhone?

No, and not from any tool. Netflix doesn't play video in a mobile browser on iPhone — netflix.com sends you to the app — so there is no web player for an extension or app to add a second subtitle line to. Netflix dual subtitles work on a desktop browser with an extension.

Does Language Reactor work on Android?

Not officially. Its FAQ lists Android among the platforms it doesn't support. The old workaround was Kiwi Browser, which was discontinued in January 2025; its extension code went into Microsoft Edge's Android Canary build, which is a developer preview rather than a supported route.

What's the closest thing to Language Reactor on iPhone?

An app that plays the video itself and draws both subtitle lines over its own player, since a phone browser can't be extended. Linglass does this for YouTube on iPhone, with tap-to-translate in context, pronunciation and a spaced-repetition deck, and it can generate subtitles for videos that have none.

Will my saved words sync between my phone and my computer?

In Linglass, yes — one account, and words saved on either device land in the same review deck along with your language settings. Words saved in Language Reactor stay in Language Reactor; there is no import between the two.