YT Transcript Summarizer

Extract transcripts from YouTube videos and summarize them with any AI — Claude, ChatGPT, Gemini, OpenRouter, or a local model.

The project ships as two complementary clients that share the same transcript-extraction logic and prompt presets:

Client	Best for	Folder
Browser extension (Chrome / Firefox)	Desktop, power users, batch processing	web_extension/ — Install on Firefox ↗
Progressive web app	Mobile, quick one-off summaries	web_app/

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How it works

1. A YouTube URL is submitted.
2. The transcript is extracted using multiple strategies with automatic fallback (6 server-side strategies in the web app, 4 in the extension).
3. If the video has no captions in the requested language, YouTube's auto-translate (tlang) is used automatically.
4. A prompt is assembled (provider, language, length, and format are all configurable).
5. The result is either sent directly to an AI API, or copied so you can paste it into any chat UI.

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Features by client

Feature	Extension	Web app
AI providers	Claude, OpenAI, Gemini, OpenRouter, Custom	Claude, OpenAI, Gemini
Web mode (open chat UI + copy)	✅	✅
API mode (call AI directly)	✅	—
Transcript download (.txt)	✅	✅
Extraction log export (copy)	—	✅
Batch queue	✅	—
Per-video settings	✅	—
Thinking mode (Claude)	✅	—
Auto-paste / auto-submit	✅	—
Text-to-Speech	✅	—
7-day transcript cache (localStorage)	—	✅
Clear cache button	—	✅
Strategy badge (shows which method succeeded)	—	✅
Share to app (Web Share API, bypasses Android clipboard limit)	—	✅
Video history	✅ (No limit)	✅ (No limit)
Dark / light theme	✅	✅
Languages	15 languages + auto-translate	15 languages + auto-translate

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Language support

Web app

The Language selector includes 15 languages: Italian, English, Spanish, French, German, Portuguese, Chinese, Japanese, Korean, Arabic, Russian, Dutch, Polish, Turkish, and Hindi.

Full native prompts are provided for Italian, English, Spanish, French, German, and Portuguese. Other languages fall back to the English prompt — the AI infers the correct output language from the transcript.

When a video has no captions in the requested language the app automatically uses YouTube's tlang auto-translate parameter, so you can always get a transcript in your chosen language as long as the video has any captions at all.

Extension

Same 15 languages as the Web app.

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Shared logic

Both clients use the same:

• Transcript extraction strategies (Android Player API, get_transcript endpoint, Timedtext API)
• Provider configuration (names, models, default models, API endpoints)
• Prompt presets (Italian, English, Spanish, French, German, Portuguese; three lengths; two formats)

The extension is plain JavaScript (ES modules, Manifest V3); the web app is TypeScript (Next.js, React, Tailwind CSS 4). The shared configuration is kept in sync between web_extension/modules/config.js and web_app/src/lib/config.ts.

The web app also has two additional server-side-only strategies (Supadata API and Piped/Invidious instance rotator) that require server-side fetch and cannot run in a browser extension.

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Repository structure

YT-Transcript-Summarizer/
├── web_extension/          Chrome / Firefox extension (Manifest V3)
│   ├── manifest.json
│   ├── background.js       Service worker: extraction, API calls, TTS
│   ├── popup.html/css      Extension popup UI
│   ├── popup.js            Popup orchestrator: init, port, job CRUD, batch
│   ├── *_paste.js          Content scripts for Claude, ChatGPT, Gemini
│   ├── tts_offscreen.*     Offscreen document for Web Speech API
│   └── modules/
│       ├── config.js           Providers, prompts, YouTube API config
│       ├── llm-api.js          AI provider integrations
│       ├── youtube-api.js      Transcript extraction strategies
│       ├── popup-state.js      Shared mutable state object
│       ├── popup-history.js    History panel
│       ├── popup-tts.js        TTS panel
│       ├── popup-render.js     Job rendering, chips, per-job settings
│       ├── popup-settings.js   Provider/settings panel
│       ├── ui-utils.js
│       └── utils.js
│
└── web_app/                Next.js PWA (mobile-first)
    ├── src/
    │   ├── app/
    │   │   ├── page.tsx        Main UI (form, prompt editor, cache, history)
    │   │   ├── layout.tsx
    │   │   ├── globals.css
    │   │   └── api/transcript/ Server-side extraction endpoint (6 strategies)
    │   ├── components/
    │   │   ├── TranscriptForm.tsx
    │   │   └── ActionButtons.tsx
    │   └── lib/
    │       ├── config.ts       Providers, prompts, language list, YouTube API config
    │       ├── youtube-api.ts  Transcript extraction strategies + auto-translate
    │       └── utils.ts
    └── public/manifest.json    PWA manifest

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Quick start

Extension

Firefox users can install directly from the Firefox Add-ons page.

For Chrome or manual Firefox installation see web_extension/README.md.

Web app

cd web_app
npm install
npm run dev

Open http://localhost:3000. For production deployment see web_app/README.md.

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License

MIT