Comment Vibe: on-device check von Kamil Dzieniszewski

Ever hit Post and instantly regretted the tone? Comment Vibe reads your comment as you type and shows you how it sounds — before the internet does.

It runs entirely on your device using Firefox's built-in AI runtime (the experimental WebExtensions AI API, Firefox 134+), and understands comments in ~100 languages. No servers, no account, no data collection.

HOW IT WORKS

Type a comment on LinkedIn, X (Twitter), YouTube, Reddit — any site with a text box.
A small badge appears next to the box showing the detected tone.
Click the badge to see why: the on-device classifier explains which tone it read, and how confident it is.
FOUR CLEAR TONE LABELS 😊 Positive — constructive and friendly 😐 Neutral — balanced and factual 😕 Negative — may come across as harsh or critical 🚫 Toxic — contains aggressive or harmful language

100% PRIVATE, BY DESIGN All analysis happens locally with an on-device multilingual model (about 340 MB, downloaded once from Mozilla/Xenova's model hub — works in English, Polish, and ~100 other languages). Your comments are never sent to any server. No account, no tracking, no analytics — and it keeps working offline once the model is downloaded.

ONE-TIME SETUP Because on-device AI in Firefox is still experimental, you turn it on yourself: • Open the Comment Vibe popup and click "Enable on-device AI" (this grants the optional trialML permission and downloads the model once). • On Firefox 134–139 you may also need to set browser.ml.enable and extensions.ml.enabled to true in about:config (on by default since Firefox 140).

REQUIREMENTS • Firefox 134 or later, on desktop. • Enough free disk/memory for the on-device model.

GOOD TO KNOW This Firefox build focuses on the tone badge and explanation. The kinder-rewrite suggestions and automatic translation available in the Chrome version rely on a generative on-device model that Firefox's AI API does not yet expose — so they are not part of the Firefox build. The tone check itself works the same way.

Comment Vibe is open source. The WebExtensions AI API it depends on is explicitly experimental, so behaviour may change between Firefox versions.