Claude for Firefox
Claude in Chrome has no Firefox edition. Browsentic runs the Claude Code CLI you already have against your Firefox tab, on your existing Claude plan.
Firefox 140 and newer
Claude
for
Firefox,
Gemini
for
Firefox
and
Codex
for
Firefox,
in
a
signed
add-on
Anthropic, Google and OpenAI ship their browser agents for Chrome. Browsentic runs their agent CLIs in a Firefox side panel, through an add-on signed by Mozilla.
Pick the agent
Agent CLIs that run in the Firefox side panel
Each of these vendors has a command line tool, and that is the part Browsentic needs. Switching between them is one click in the side panel.
Gemini for Firefox
Gemini in Chrome is part of Chrome. Antigravity, Google’s agent CLI, runs Gemini from your machine, and Browsentic points it at the Firefox tab in front of you.
Codex for Firefox
OpenAI’s own browser agent lives in ChatGPT and a Chrome extension. The Codex CLI drives Firefox here, on the ChatGPT plan you already pay for.
Mistral Vibe
betaMistral’s CLI. Beta while its session handling settles, so expect the odd retry on a long run.
Grok Build
betaxAI’s CLI. Beta, and the least proven: its rules are checked against the real CLI, but no full conversation in the panel has run on it yet.
Cursor CLI
betaCursor’s agent without the editor, on your Firefox tab. Its tool calls, images and approvals were tested against the real CLI. Beta until it has carried long conversations in the panel.
Qwen Code
betaAlibaba’s open source agent CLI, on the model provider you set up for it. Beta; it does not answer until that provider is configured.
OpenCode
betaAn open source agent CLI, OpenCode 1 or 2, that works with most model providers. Beta; sign a provider in first, because the free Zen models refuse a contained run.
What is specific to Firefox
How the Firefox build differs from Chrome
It is signed by Mozilla, stays installed and updates itself. Nine tools that need Chrome’s DevTools Protocol are missing.
It stays installed
Mozilla signs the build, so it survives restarts like any other add-on. A build loaded through about:debugging is removed at the next restart.
It updates itself
Firefox checks the release page for a newer signed build about once a day and installs it. Check for Updates under the gear in about:addons does it immediately.
Nine tools are missing, and the agent is never offered them
The trusted click, both captcha tools, the four diagnostics tools and the two page-code tools are built on Chrome’s DevTools Protocol, which Firefox does not expose. The Firefox build leaves them off the list it publishes, so the agent never plans around them. A stale recording that names one gets UNSUPPORTED with a hint instead of failing quietly.
Your profile, in whatever container the tab is in
It drives the real tab you are looking at, with the cookies, container and two-factor state it already has. Nothing new is launched, so nothing is re-authenticated.
Install
Install the signed Firefox add-on
Release builds of Firefox install only add-ons signed by addons.mozilla.org. Browsentic’s Firefox build is a signed .xpi attached to every GitHub release.
-
01
Run setup for Firefox
It installs Browsentic Bridge, opens the add-on for that exact version in Firefox and waits for it to connect. On a Mac or on Windows, the app does the same from its Get the Firefox add-on button.
shnpx browsentic@latest setup --browser firefox -
02
Add the signed add-on
Accept both prompts: one lets github.com install software, one adds Browsentic, with the permissions it asks for. To install from the file instead, download the .xpi, open about:addons, press the gear and choose Install Add-on From File.
-
03
It pairs by itself
The add-on finds Browsentic Bridge and connects, with no code, and the session key it gets survives restarts. If it asks for a code, enter the one setup printed; run browsentic pair if you need another.
shnpx browsentic pair
Firefox add-on, signed by MozillaIf setup says the file is not attached yet, Mozilla is still signing that version. It usually appears within minutes.
Questions
Questions about Browsentic in Firefox
Is there a Claude extension for Firefox?
Not from Anthropic: Claude in Chrome is Chrome only. Browsentic runs Claude Code, the CLI you already have, against your Firefox tab, through an add-on signed by Mozilla. It uses your existing Claude plan, with no API key.
Can I use Gemini in Firefox?
Through Antigravity, yes. Google’s Gemini in Chrome feature is part of Chrome, but Antigravity is Google’s agent CLI and runs on your machine. Install it, log in once and pick it in the Browsentic side panel, which then runs on Gemini.
Why is the add-on not on addons.mozilla.org?
It is signed by Mozilla on the unlisted channel and attached to each GitHub release instead of being listed in the store, so a release reaches Firefox the day it ships. Firefox still verifies the signature, shows you the permissions and updates it for you.
Which Firefox versions work?
Firefox 140 or newer, on macOS, Windows or Linux. Developer Edition and Nightly can also load the unsigned build from a source checkout, which is for working on Browsentic, not for using it.
What can Firefox not do?
Use nine tools: the trusted click, the two captcha tools, the four diagnostics tools and the two page-code tools, which all need Chrome’s DevTools Protocol. Everything else is the same: reading the page as structure, clicking, typing, navigating, screenshots, tabs, recordings, site maps and WebMCP.
Give your browser a superpower.
Free and open source under Apache 2.0, with no API key, subscription or account. One line installs Browsentic Bridge and opens the extension’s store page. Nothing connects until you pair the two.