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YouTube subtitle translator — paste a link, tap a word

Paste any YouTube link into CIRCØ and tap any caption word — or select a phrase — to translate it instantly while the video plays. No account, no install, no download. Includes background audio playback (available on Android), an OLED Pocket Mode with Screen Wake Lock, and works with both auto-generated and manual captions, with De-forced language handling and a YT pill for YouTube-native languages.

How it works

1. Open circ0.com and click Open YouTube Video on the main button (or paste a YouTube link directly).
2. Paste any YouTube URL — youtube.com/watch?v=, youtu.be/, youtube.com/shorts/, or music.youtube.com — and press Open.
3. Captions load automatically via YouTube. If the video has only one language (e.g. Russian auto-generated), the Source language (FROM) auto-switches to it. If multiple tracks exist, a bottom toast says “Multiple subtitles available — select your source language in the dropdown” and the FROM dropdown shows the YouTube options with a YT pill.
4. Set the To language (your target), then tap any caption word or select a phrase to translate it on the fly. The video pauses, the popover appears, and the word is saved to your vocabulary.

Player features for YouTube

• Tap-to-translate caption overlay — native YouTube captions are suppressed in favor of CIRCØ's interactive overlay; tap a single word or expand to phrase/sentence.
• Background audio playback (Android only) — keep listening to videos, lectures, and foreign language podcasts in the background on Android devices with notification shade controls, thumbnail artwork, elapsed time scrubber, and Bluetooth / earbuds play/pause support via the Media Session API.
• OLED Pocket Mode & touch lock — tap the headphones icon in the player toolbar to engage Screen Wake Lock with a pure-black (#000) screen. Slide your phone into your pocket without accidental touches; hold for 2 seconds (or press Esc) to unlock. Available on Android and on iPhone with iOS 16.4+ (older iOS versions show a “not supported” notice, since Apple added the Screen Wake Lock API in 16.4). It stops accidental pocket touches from pausing or seeking the video.
• De-forced translation — captions are fetched for your FROM language via &tlang and LibreTranslate batch fallback, so Spanish → English and English → Spanish (and Russian → English) stay in sync even when YouTube only has one track.
• Auto-switch source — opening a Russian video after a Spanish one flips FROM from es to ru automatically when only Russian is available.
• Keyboard shortcuts — J previous caption, K next caption, L replay, [/] sync ∓0.2s, ←/→ seek or caption-scrub when translating, Space play/pause, ↑/↓ volume — works even when the YouTube iframe would otherwise steal focus.
• Read Along & timing — active cue highlighted, click a cue in the sidebar to jump, shift sync if captions are out of time.
• Local & private — video streams from YouTube, captions are fetched server-side; only the text you tap is sent for translation.

Background playback & Pocket Mode — how it works on mobile

If you use CIRCØ to listen to long-form YouTube podcasts, interviews, or lectures in a foreign language on your phone, you can take playback on the go:

• Android (Background listening & Lock Screen): Android Chrome and Chromium browsers support true background playback. When you background the browser or switch to another app, CIRCØ keeps audio playing continuously and displays the YouTube video title, thumbnail artwork, elapsed time scrubber, and playback controls in your notification shade and lock screen.
• Pocket Mode (Android & iPhone on iOS 16.4+): Tap the headphones icon next to the mode selector in the player toolbar. The screen immediately blacks out (turning off pixels on OLED displays to save battery) and locks all touch gestures so fabric contact in your pocket won't pause or seek. To exit, press and hold for 2 seconds or press Esc on a keyboard. On older iOS versions without the Screen Wake Lock API, tapping the icon shows a “not supported” notice instead.
• Why YouTube background audio is Android-only: On iPhone (iOS), Apple's WebKit browser engine automatically freezes and suspends embedded YouTube iframes the moment Safari or the PWA is backgrounded, regardless of web page code. On iOS, Pocket Mode provides the seamless alternative — keeping the display awake under an OLED black touch-shield so playback continues without interruption in your pocket.

Great for language learning from YouTube

Watch in your target language and translate only the words you don't know, building vocabulary in context. Every tap is saved to your history and powers the Vocabulary Quest spaced-repetition review. It works for vlogs, language lessons, news, and even auto-generated captions — the same tap-to-translate you use for local video files.

Can I listen to YouTube in the background or with the screen off?

On Android: Yes! CIRCØ supports true background audio playback and notification shade controls via the Media Session API. You can switch apps or lock your phone, and playback continues with full play/pause and scrub controls.

On iPhone (iOS): Background audio playback for YouTube is currently not supported due to iOS WebKit platform limitations (Apple freezes iframe media processes when Safari is backgrounded). However, iPhone users on iOS 16.4+ can use CIRCØ's Pocket Mode (the headphones button) to listen on the go: it keeps the screen awake while rendering a pitch-black (#000) OLED touch-shield, allowing you to pocket your phone without accidental taps or playback interruption.

Playback paused when I switched apps — how do I resume?

Some Android phones pause background media aggressively when you leave the browser (Pixel battery optimization is a known case). If CIRCØ pauses, swipe down and tap play on the media tile — playback resumes from the same position. If it happens every time: set Chrome's battery usage to Unrestricted (Settings → Apps → Chrome → Battery), and for screen-off listening use Pocket Mode (the headphones icon), which also suspends auto-pause at subtitles.

What is tap-to-translate for YouTube captions?

YouTube's own captions are not interactive. CIRCØ replaces them with an interactive overlay: each caption is tokenized into tappable words. Tapping a word pauses the video, shows the translation, an example sentence, and (for single words) a generated scene image. Selecting a phrase translates the whole selection. This is the same experience as reading an EPUB or PDF in CIRCØ, but for video.

How is this different from YouTube's auto-translate?

YouTube can auto-translate captions in its own player, but it translates the entire track at once and you can't look up a single word in context. CIRCØ keeps the original captions and translates only the word you tap, with dictionary context, pronunciation, and vocabulary saving. It also lets you keep the FROM language as the original (e.g. Russian) while translating to your TO language (e.g. English), rather than replacing the whole track.

Which languages are supported?

20 built-in languages — English, Spanish, French, German, Japanese, Chinese, Russian, Portuguese, Italian, Korean, and 10 more — plus any additional language YouTube itself provides for that specific video. Extra YouTube-native languages appear in the FROM dropdown with a YT pill (e.g. Ukrainian). You can translate between any pair; if YouTube has no direct track, CIRCØ renders an auto-translated one via &tlang.

Do I need to download the video or install an extension?

No. The video streams from YouTube via the YouTube IFrame API — no file download, no Chrome extension, no desktop app. It works in Chrome, Firefox, Safari, and Edge on desktop and mobile. For local files, use the video subtitle translator instead.

Is it free and private?

Yes. CIRCØ is free, no account. The YouTube video is not uploaded anywhere; captions are fetched server-side. Only the caption text you tap is sent for translation. Your watch position and vocabulary stay in your browser (localStorage/IndexedDB). See privacy and terms.

Questions? Email circ0@circ0.com. See our privacy policy and terms of use.