BelliedMonkey Translator — bilingual pages, dual video subtitles, and review cards from what you actually read.
It is a free, open source browser extension that shows web pages and video subtitles in two languages at once, and can turn the sentences you actually read into review cards. It runs in Safari on iPhone, iPad and Mac, and in Chrome and Firefox. You bring your own translation engine, or use a free channel that works with no setup.
It is free with no ads, no paid tier and no in-app purchase, and the source code is public. The cost that does exist is the translation itself: if you plug in your own AI service key, you pay that provider directly at their prices, and the extension neither marks that up nor takes a cut. The free channel costs nothing but is a general-purpose machine translation rather than an AI model.
Four things decide whether you keep using one. Where the text goes — whether requests reach the translation provider directly or pass through the tool maker's servers. Whether you can use your own key and your own model, or are locked to whatever the tool ships. Whether video subtitles are translated sentence by sentence or cue by cue, because cue-by-cue produces fragments. And whether it works on the device you actually read on, which for most people includes a phone.
If you turn learning on, sentences you genuinely stopped and read — not ones you scrolled past — are saved together with the page they came from, and come back on a forgetting curve. Reviews rotate between reading, listening and writing, with sentence notes and read-aloud, and each grade tells you when that sentence is due again. It is off by default, and turning it off leaves translation exactly as it was.
The text you asked to translate goes to the translation provider you chose, sent directly by your browser using your key. Nothing else leaves unless you deliberately switch sync on and sign in, in which case your saved sentences and translations, the URL and title of the page they came from, and your review times are stored for your account so another of your devices can read them. There is no tracking, no telemetry and no advertising.
A free channel needs no key and no account. Beyond that you can enter the key for your own AI service, or the address of any compatible endpoint — a company gateway, a proxy, or a model you host yourself. The current list of built-in providers lives in the source repository rather than in marketing copy, so it is always the list the software actually ships with.
Built-in translation replaces the page: the original is gone, so you cannot check a sentence you doubt, and you learn nothing from reading it. This keeps both languages on screen, lets you choose the engine doing the work, and can turn what you read into review material. If you only want to skim a page once in a language you do not care about, the built-in one is fine and faster to reach.
Yes, the whole thing — extension, host app and the site — is public at github.com/belliedmonkey/belliedmonkey-translator. The package the website offers for direct install is built from the same source that is submitted to the stores, so you can read exactly what you are running rather than take a privacy claim on trust.
Everything is on your device unless you turned sync on, so deleting the app takes it with you. If you did sync, deleting a source or your account removes it from every device. You can also export your saved sentences at any time, so leaving does not mean losing what you collected.
Installed it? Turn it on →See also: YouTube dual subtitles · translating pages in Safari on iPhone