Browser Extension

Capture downloads from Chrome, Edge, Brave, and Firefox and hand them to MacGet with cookies and referrer intact.

The capture extension intercepts downloads as they start in your browser and hands them to MacGet, including the cookies and referrer needed for downloads behind a login.

How it works

Browser download starts
  → extension collects { url, cookies, referrer, user-agent, filename, size }
  → sends it to the native-messaging host (MacgetCaptureHost, bundled in Macget.app)
  → host writes it as JSON into ~/Library/Application Support/Macget/incoming/
  → MacGet ingests it and downloads with its multi-threaded engine

The browser's own download is cancelled only after MacGet acknowledges the handoff. A missing or disabled host can never make a download silently disappear — worst case, the browser downloads it normally.

Everything happens on your machine over local native messaging. The extension contains no code that contacts a remote server. See the privacy policy for the full detail on what it collects and why.

Setup

Enable capture in MacGet

Settings → Browser integration → turn on Auto-capture downloads from the browser extension.

This installs the native-messaging host manifests for every supported browser and starts watching the inbox directory.

Install the extension

Follow the instructions for your browser below.

Keep MacGet at a stable path

The host path is re-stamped each time MacGet launches, so moving the app and relaunching is fine. But the manifests point at wherever MacGet last ran — if you move it and don't relaunch, capture stops working.

Chrome, Edge, and Brave

Install it from the Chrome Web Store. The same listing works on Edge and Brave.

To run it from a clone of the repository instead:

Open chrome://extensions (or edge://extensions, brave://extensions).
Enable Developer mode.
Choose Load unpacked and select the chromium/ folder from the repository.
Confirm the extension ID is knccbiljmilfmhfellkfbdmilpbdkgni.

The ID is not cosmetic

MacGet's native-messaging host manifest trusts exactly two extension IDs and no wildcards: ldmhmgglgemkoogpokfcgplbpfokcejl (the published Web Store build) and knccbiljmilfmhfellkfbdmilpbdkgni (an unpacked clone, pinned by the key field in its manifest). Any other ID is refused — which is the point: it stops another extension on your machine from talking to MacGet.

Firefox

Run ./build.sh once in BrowserExtension/ to sync shared files into firefox/.
Open about:debugging#/runtime/this-firefox.
Choose Load Temporary Add-on and select firefox/manifest.json.

Temporary add-ons are removed when Firefox restarts. Firefox 121 or later is required.

What gets captured

Field	Why it's needed
URL	The file to download
Cookies for that URL	So logged-in downloads work outside the browser
Referrer	Some hosts reject requests without one
User-Agent	Some hosts serve different content per client
Filename	The browser's suggested name
Size and MIME type	Lets MacGet plan chunks before probing

Cookies are read scoped to the download URL specifically — not your whole cookie store.

Media pages

On a recognised media host, the extension can hand over the page URL along with any stream manifests it observed, so MacGet's extractor can resolve formats. This path only does anything when media extraction is enabled in MacGet.

Troubleshooting

Downloads still go to the browser. Check that browser integration is on in MacGet's settings, and that MacGet has been launched at least once since you last moved the app.

Firefox forgets the extension. Temporary add-ons don't survive a restart. That's a Firefox constraint on unsigned add-ons, not a MacGet bug.

The extension ID doesn't match. You likely loaded a copy without the key field from the manifest. Load the chromium/ folder from the repository directly.

Browser Extension

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