Sakutto

Sakutto is an unofficial extension for Chrome and Firefox that translates web pages on your device. It runs PLaMo 3 Translate through a pinned wllama build. Every translated line is written by PLaMo: a page waiting for the model keeps its source text rather than showing a draft from another engine. On Chrome, Chrome's Translator API is used only for the language pairs PLaMo does not support. Firefox uses PLaMo only. Not affiliated with Preferred Networks, Inc. Built with PLaMo.

The extension is free and open source (MIT). It has no ads and no paid features. The model weights are not in this repository or in the extension package.

Install

Install Sakutto from the Chrome Web Store:

https://chrome.google.com/webstore/detail/mhlbjjijfkoghmcjndgdimhdlfkhadfl

To build and load it yourself instead:

1. Install Node.js 24 and pnpm 12.
2. Clone this repository and run pnpm install.
3. Build the translation runtime and the extension (see Build).
4. Chrome: open chrome://extensions, turn on Developer mode, choose Load unpacked, and select .output/chrome-mv3.
5. Firefox 153 or later (Windows first): open about:debugging, choose This Firefox, Load Temporary Add-on, and select .output/firefox-mv3/manifest.json. See docs/FIREFOX.md.

Shortcuts

Action	Windows / Linux	Mac
Translate the page, or restore the original	Alt+A (Firefox: Alt+Shift+A)	Option (⌥)+A (Firefox: Alt+Shift+A)
Switch between replaced text and bilingual text	Alt+B (Firefox: Alt+Shift+B)	Option (⌥)+B (Firefox: Alt+Shift+B)
Translate the selection	Alt+S (Firefox: Alt+Shift+S)	Option (⌥)+S (Firefox: Alt+Shift+S)
Translate the text you are writing	Alt+T (Firefox: Alt+Shift+T)	Option (⌥)+T (Firefox: Alt+Shift+T)
Translate typed text (on the typed text page)	Ctrl+Enter	⌘+Enter

The same actions are in the toolbar popup and the right-click menu. Chrome keeps these keys, so you change them in Chrome's own editor: the settings page has a Keyboard shortcuts panel, and the popup has a Change shortcuts link, both of which open chrome://extensions/shortcuts. Firefox uses Alt+Shift+letter by default so the Windows menu bar is not taken, and Change shortcuts opens Firefox's own editor. The key list in the popup and the hint on the translate button follow whatever you bind there. A key Chrome has assigned is delivered as an extension command even while a text field is focused, so the page still translates. If Chrome never assigned a command, the default is handled on the page instead: the keydown does reach the page (including in a textarea), and Sakutto leaves it unprevented there so Option+letter can type a character. That in-page default does not run on chrome:// pages or in the PDF viewer, where the content script is not injected. A key you cleared in Chrome's editor stays off; an old install that never received a key still gets the in-page default. Chrome reads Alt in an extension shortcut as Option on a Mac, so the keys are the same letters. Reloading an unpacked build from the same folder can keep a previously cleared binding in Chrome's editor. Alt+D is not a default, because Chrome on Windows and Linux uses it for the address bar.

Typed text

While a message box, a textarea, or another editable field is focused, Alt+T (Option+T on a Mac; Alt+Shift+T on Firefox) or the あA button next to the field previews an on-device translation of what you are typing. Press the same shortcut again, or Ctrl+Enter (⌘+Enter on a Mac), to replace; Restore original puts the draft back. The preview has a language menu, and settings can skip the preview so one shortcut press translates and replaces. Japanese drafts go to English (or to your saved target if that is not Japanese); other drafts use the saved target, until you pick another language. Password fields and sites set to never translate are left alone. You can hide the あA button in settings. A Chrome-assigned page shortcut still translates the page from a field (onCommand). An unassigned default's keydown still reaches the field; Sakutto does not prevent it, so Option+letter can type. Compose keeps its shortcut in the field. The same PLaMo model as page translation is used; the built-in translator is not.

The popup has a Translate typed text button, and the options page has the same button. It opens a small extension page with a source box and a result box, so you can type or paste a paragraph and translate it without touching a page. It uses the same PLaMo model, the same licence consent, and the same load flow as page translation, and the direction follows the same target-language setting. The built-in translator is not used there: typed text is translated by PLaMo only, and a language PLaMo does not support is refused in the page rather than quietly handed to Chrome. The result has a Copy button.

Languages

PLaMo 3 Translate supports 53 languages in either direction. The source language is detected from the page. The default target language is the browser UI language, or English when that language is not one of the 53. The popup can set a different target language for the current site.

Eleven further languages (cs, da, el, fi, kn, no, pt, ro, sv, tr, uk) are translated only by Chrome's built-in translator, and only in Chrome. Firefox hides those targets. Languages that PLaMo supports stay untranslated until the model is ready.

The interface itself is translated into 14 languages: English, Japanese, Korean, Chinese (Simplified and Traditional), Spanish, Portuguese (Brazil), French, German, Italian, Russian, Vietnamese, Thai, and Indonesian. Chrome picks the catalog that matches the browser UI language and falls back to English. To add one, see docs/TRANSLATING.md.

Privacy

Translation runs on your device by default. The extension does not send page text, selections, your glossary, or translations to the developer. There is no account, ads, or telemetry. The built-in engine's own network request is the model download from Hugging Face. If you turn on the experimental local server in Settings (mlx_lm.server, LM Studio, or another OpenAI-compatible process on this computer), the text to translate is sent only to the address you set — not to the developer. Accuracy is not guaranteed. Read the policy at PRIVACY.md or https://jammaru.com/sakutto/privacy/.

Local server (experimental)

The default engine is the packaged wllama runtime (WebGPU or CPU). Settings can point PLaMo requests at an OpenAI-compatible server on this machine instead. That path is experimental: accuracy is not guaranteed, and translations can differ from the built-in engine, including mistranslations. A Mac check of MLX 4bit, 8bit, and bf16 showed errors the built-in engine did not; the difference comes from quantization numerics, not from a different request. Use raw /v1/completions with Sakutto's PFML3 prompt; chat completions are not used. Recipes:

• mlx_lm.server — default http://127.0.0.1:8080/v1, PLaMo MLX-4bit weights from the PLaMo 3 Translate collection
• LM Studio — default http://127.0.0.1:1234/v1

In LM Studio, set the server-side sampler to temperature 0 / greedy. Prompt parity is measured against mlx_lm.server and PLaMo's serve.py; LM Studio's BOS handling is unverified.

Design, model pins, and what was not measured on Linux: docs/design/mlx-backend.md. Mac timings: bench/README.md.

Build

pnpm install
pnpm build:wllama   # once, with Docker; see docs/BUILDING.md
pnpm verify:wllama
pnpm build          # production build in .output/chrome-mv3
pnpm build:firefox  # Firefox 153+ MV3 in .output/firefox-mv3
pnpm zip            # Chrome Web Store zip in .output
pnpm zip:firefox    # Firefox zip in .output; then pnpm source:firefox for the AMO source zip

pnpm build:wllama compiles the pinned wllama commit d275dac inside the emscripten/emsdk:4.0.20 container. The wasm, workers, and model weights are not committed. pnpm build and pnpm zip refuse to run until that build has been verified. pnpm zip also checks that the package contains the runtime and the license texts, and that it does not contain model weights, source maps, or install-time host permissions.

pnpm dev            # development build
pnpm lint
pnpm typecheck
pnpm test
pnpm test:e2e       # local fixtures; does not download the model

pnpm test:e2e builds a test package that translates inside the page. That package is not the release build. The release build does not include the test translator.

pnpm bench loads the built extension in headless Chromium (Playwright's Chrome for Testing build, because branded Chrome refuses --load-extension) and translates four fixed local pages with the real 0.8B model: a long article, a news article, a docs page, and a client-rendered page. It also runs a short engine probe for time to first token and output speed. Pass --pages-only, --engine-only, or --sweep (thread, context, and batch sizes). The model is cached under bench/.cache/ after a SHA-256 check. Build with SAKUTTO_E2E_REAL=1 pnpm build first so the harness can script the local pages. Results are written to bench/results/.

pnpm bench:mock and pnpm bench:live measure whole pages the way a reader experiences them, on eight fixtures in bench/pages that each isolate a different cost (a long article, a short lead with a long tail, many short cards, one very long paragraph, a sidebar, mixed UI, a headline inside the article header, and late-mounted content). Every run appends to bench/history/pages.jsonl, so a later commit can be diffed against an earlier one on the same pages. pnpm bench:serve opens those fixtures in your own browser. See bench/README.md for the metrics, the mock-versus-live distinction, and how to add a fixture.

pnpm icons regenerates the PNG icons from scripts/generate-icons.mjs.

pnpm i18n:check compares every catalog in public/_locales against English for missing keys, placeholder tokens, and empty messages. pnpm i18n:draft <catalog> <language> drafts a catalog from English with the same PLaMo model the extension ships. Both are described in docs/TRANSLATING.md.

Permissions

Permission	Why it is requested
storage	Saves the target language, reading style, and other settings.
unlimitedStorage	Keeps the downloaded model and the translation cache on the device.
offscreen	Runs the translation runtime in a document whose workers outlive the service worker.
activeTab	Reads the current page after you open the popup or use a command.
scripting	Injects the content script into the active tab after you ask for a translation.
contextMenus	Adds Translate page and Translate selection to the right-click menu.

Optional host permissions (https://*/* and http://*/*) are requested only when you turn on automatic translation for a site. Nothing is requested for every site at install time.

Support

There is no monetisation point in Sakutto. It is completely free, with no ads and no paid features.

I started it because I wanted a translation extension like this myself, and I published it because it turned out to be needed by more people than I expected. I have no plans to charge for it or to add ads.

Continuing development still takes time and money, so I opened GitHub Sponsors. If you like Sakutto, I would be glad of your support.

• $5 a month (Supporter): a plan for cheering on Sakutto's ongoing development.
• $10 a month (Backer): for anyone who wants to back it further. The amount changes nothing about the software.
• One-time: any amount, once, if a subscription is more than you need.

Neither tier adds limited features or priority support. The money goes towards new features, translation quality and speed, and ongoing maintenance. Whether you sponsor or not, Sakutto stays completely free and open source. https://github.com/sponsors/jammaru

Contributing

Open an Issue first, then a pull request for that Issue if you can. That path is fully welcome. A PR is very much wanted; an Issue by itself is also enough. Please use the issue forms, and do not paste private page content. Questions are often faster in Discord.

• CONTRIBUTING.md (日本語: CONTRIBUTING.ja.md)
• Code of Conduct
• SECURITY.md

Licenses

• Project code: MIT. See LICENSE. Copyright 2026 jammaru.
• PLaMo 3 Translate: PLaMo Community License. The texts are in licenses/PLaMo-Community-License-ja.txt and licenses/PLaMo-Community-License-en.txt, and the same copies are packed into the extension. Personal and academic use needs no registration. Under Article 3 the model's license allows commercial use only with prior registration on PFN's form (https://forms.gle/mTL8tBLrMYXKNZD56) and income or sales for you or your affiliates of no more than 1 billion yen in the most recent fiscal year; otherwise commercial use needs a separate commercial license from PFN. This repository's MIT license covers Sakutto's own code, not the model weights.
• llama.cpp, wllama, the Emscripten runtime, the Dawn WebGPU library, and Svelte: see NOTICE and THIRD_PARTY_NOTICES.md.
• scripts/bench/fixtures/kyoto.html is a CC BY-SA 4.0 Wikipedia derivative. It is not covered by the MIT license and is not part of the extension package.

Japanese documentation: README.ja.md.