Sada

Sada

Arabic subtitles for English YouTube, translated on your device.

A Chrome extension that renders Arabic subtitles over English YouTube videos by translating the video's own captions entirely in the browser, using a bundled NLLB-200 model. No account, no cloud translation service, and caption text never leaves the machine.

Role

Solo

Year

2026

Status

Live

type

Extensions

Built with

JavaScriptManifest V3transformers.jsNLLB-200WebGPUWASM

Where to find it

Source

projects/sada-logo.png2400×1350

What it is

Auto-translated captions on YouTube mean your viewing history goes to a translation service. Sada does the same job without that: the model and runtime download once at install, and after that the engine runs with remote models disabled.

At runtime the only network traffic is YouTube itself, meaning the video and its caption cues fetched same-origin, plus extension-local asset loads. Any request to a third-party origin would be a bug, and the privacy claim is written to be falsifiable rather than reassuring.

Challenges

A line taken out, a line put in. The problem first, then what actually replaced it.

A translation model in a browser tab

NLLB-200 is not a small model, and running it in the page means competing with the video for memory and compute on the same machine that is decoding 1080p.

The distilled 600M variant runs through transformers.js on WebGPU where available and falls back to WASM otherwise. Assets are fetched once at install rather than per session, so the cost is paid one time.

Subtitles have to keep up with the video

Translation takes time, and a subtitle that arrives after the line has been spoken is worse than none. The viewer reads one sentence while hearing the next.

Cues are translated ahead of the playhead rather than on demand, so the work happens during the gap before the line is needed instead of after it has passed.

What it is

Challenges

A translation model in a browser tab

Subtitles have to keep up with the video

Results

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