Demirline
Dual subtitles
Source + translation, sentence-aligned. Source track is chosen automatically and can be changed per video.
Chrome extension · YouTube language learning
Learn from real video with dual subtitles
Original captions plus AI translation on YouTube. Click words, repeat sentences, and translate paragraphs on any site.
If the Chrome Web Store listing is not live yet, the button stays disabled.
Learning glued to the video
Subtitles, dictionary, and translation in one flow — with your own API key.
Sentence repeat
Press S to re-hear a line; optional auto-pause at sentence boundaries keeps the pace yours.
Word dictionary
Click a caption word or select text on any site (Alt+W). Definitions with pronunciation support.
Translate anywhere
Paragraph (Alt+T) and sentence (Alt+S) translation — bubble or inline insert.
Four AI providers
OpenAI, Anthropic (Claude), Google Gemini, or OpenRouter. Stored only in your browser; sent only to the AI provider you choose.
Multilingual UI
Interface in 10 languages; follows your browser language. Pick target language and models in settings.
See it in action
Settings, quick popup, dual subtitles, and dictionary — real extension UI.
How it works
Three steps. No Demirline account — translation goes to the provider you choose.
Install
Add Demirline from the Chrome Web Store. Permissions for YouTube and AI hosts are listed in the manifest.
Add an API key
Open Settings, pick a provider, paste your key. The key is stored only in the browser and never sent to content scripts.
Watch and learn
Open a captioned video. Read dual lines, look up words, repeat sentences.