YouTube Bilingual Subtitles — AI by finder

Watch YouTube videos in any language — with real-time AI bilingual subtitles.
This extension automatically layers translated subtitles directly on top of YouTube videos as you watch. Original captions and AI translations appear together, perfectly time-synced.
How to Use
Install the extension
Get a free DeepSeek API key → platform.deepseek.com/api_keys
Open any YouTube video with captions
Click the extension icon → paste your API key → choose target language
Translated subtitles appear automatically on the video
Features
Dual Subtitles: Original text on top, AI translation below
AI-Powered: DeepSeek V4 for fast, accurate translations (~$0.00015 per video)
Three Display Modes: Bilingual / Translation Only / Original Only
Smart Cache: Re-watch a video costs zero API — translations load instantly from local cache
Export SRT: Download bilingual subtitles with timecodes
Customizable Display: Adjust font size, subtitle position, and margins
7 Target Languages: Chinese, English, Japanese, Korean, French, German, Spanish
Lightweight: No account, no tracking, no server — everything runs in your browser
Privacy
Zero data collection — your API key stays in local browser storage only
No server — API calls go directly from your browser to DeepSeek
No tracking — no analytics, no telemetry, no ad networks
Requirements
A free DeepSeek API key
YouTube videos must have captions enabled (auto-generated or manual)