YouTube AI Subtitle Translator

Translate YouTube captions with AI, right on the watch page. FEATURES • Transcript panel — timestamped list or paragraph view of translated captions, synced with playback. Click any line to seek. • On-video subtitle overlay — translated subtitles rendered over the video (replace or bilingual mode, adjustable font size). Works in theater and fullscreen mode. • AI video summaries — TL;DR plus a clickable timeline of sections, with three detail levels (brief / standard / detailed). • Manual or automatic translation — by default, nothing is translated until you click the Translate button, so you stay in control of API usage. • Smart caching — translations and summaries are cached locally per video, so revisits are instant. Built-in cache manager with search and filters. TRANSLATION ENGINES (bring your own) 1) Claude CLI — runs through a small local server included in the project (requires the Claude Code CLI and a Claude subscription). Nothing is sent anywhere except to Anthropic via your own CLI. 2) Gemini API — uses your own Gemini API key. For summaries, only the video URL is sent so Gemini can analyze the video directly. PRIVACY • No analytics, no tracking, no third-party servers. • Your API key is stored only in Chrome's local extension storage and is sent only to Google's Gemini API. • Caption text is sent only to the translation engine you configure.