Kokoro TTS Engine Privacy-friendly offline TTS engine (82M param and open-weights)
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The "Kokoro TTS Engine" extension adds around ten new English text-to-speech voices to your browser. It downloads the required model data once (based on your preferences) and stores it in the browser cache for future use. All speech synthesis is performed fully offline, ensuring maximum privacy—your text is never sent to external servers, unlike most built-in "natural-sounding" browser TTS engines. The extension has no interface. Configuration is done via the options page, after which it can be used seamlessly in any extension or web page that relies on the Speech Synthesis API.

Features

FAQs

  1. What is "Kokoro TTS Engine" extension?

    Recent advances in large language models (LLMs) have enabled the creation of highly natural-sounding voices. Kokoro is one such solution, built on an 82M-parameter model that generates speech directly from text input.

    This extension runs the Kokoro model locally inside a background worker, converting text to speech without any server interaction. Unlike most browser-based TTS engines, which transmit your data to external servers, Kokoro operates entirely offline—making it a privacy-friendly alternative.

    The extension supports multiple processing backends: CPU, GPU (WebGPU), and WASM. For best performance, we recommend using WebGPU mode. If your browser does not support WebGPU, you can fall back to the WASM engine.

    Please note that text-to-speech conversion is CPU-intensive. For smooth performance, a high-performance device is recommended. If you notice delays between sentences, try switching engines or lowering the data type precision. Once you've tuned your settings for optimal performance, it is advisable to reset the extension to clear old cached data.

  2. recommended "Libre Email Client" extension for Chrome, and Edge browsers.

    "Libre Email Client" is a full-featured IMAP email client that runs entirely in your browser, syncing mail from any IMAP server to a local Maildir store (in browser storage or a chosen directory) via a compiled WASM core with native TLS. It supports multiple accounts, server-side search, conversation threading, automatic and manual sync, message filters with move/stop actions, and an optional native client for local file operations like Spam/Archive/Trash overrides.

  3. Does this extension come with training data, or does it fetch them from a remote server?

    The extension does not include training data upon installation. The first time you use a Kokoro TTS engine, it automatically downloads the required data from the web. For your convenience, a progress window will open showing the download status and resource URLs. Please keep this window open until the process completes; it will close automatically once all resources are fetched.

    If you change the precision settings in the options page, new training data will be downloaded the next time you use the engine. All downloaded data is stored in the extension's internal cache. If you've tested multiple precision modes, it is recommended to use the Factory Reset button to clear redundant cached data.

  4. What's new in this version?

    Please check the Logs section.

  5. How can I use this extension?

    Unlike most extensions, this one does not include a standalone user interface. Instead, it integrates its TTS engines directly into the browser's default voice list via the Speech Synthesis API. Any web page or extension that relies on this API will automatically have access to these additional voices.

    Currently, the following new TTS voices are appended to your browser's default list:

    • Kokoro Heart
    • Kokoro Alloy
    • Kokoro Aoede
    • Kokoro Bella
    • Kokoro Jessica
    • Kokoro Kore
    • Kokoro Nicole
    • Kokoro Nova
    • Kokoro River
    • Kokoro Sarah
    • Kokoro Sky
    • Kokoro Adam
    • Kokoro Echo
    • Kokoro Eric
    • Kokoro Fenrir
    • Kokoro Liam
    • Kokoro Michael
    • Kokoro Onyx
    • Kokoro Puck
    • Kokoro Santa
    • Kokoro Emma
    • Kokoro Isabella
    • Kokoro George
    • Kokoro Lewis
    • Kokoro Alice
    • Kokoro Lily
    • Kokoro Daniel
    • Kokoro Fable

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What's new in this version

Version--
Published--/--/--		Change Logs:
    Last 10 commits on GitHub
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    Need help?

    If you have questions about the extension, or ideas on how to improve it, please post them on the  support site. Don't forget to search through the bug reports first as most likely your question/bug report has already been reported or there is a workaround posted for it.

    Open IssuesIssuesForks

    Permissions are explained

    PermissionDescription
    storageTo keep user preferences
    unlimitedStorageTo keep training data on the cache storage. It requires around 300M bytes max
    ttsEngineTo extend the built-in TTS engine of the browser
    offscreenTo play audio results in the background page

    Recent Blog Posts