Troubleshooting

Work top to bottom. The order is cheapest check first.

The add-on is reported as corrupt

"Corrupt" from the legacy add-on path almost always means the loader never ran, not a broken XPI. The fastest fix is to let the installer put the files in the right place; if you prefer to do it by hand, follow the manual path below.

Use the installer

1. Open the browser with the "corrupt" add-on.
2. Download and run the installer for your OS from the latest release.
3. In the tab it opens, pick the browser and the components to install (configuration files and/or utils), and complete the install.
4. Restart the browser.

Install by hand

1. Check about:config for xpinstall.signatures.required. It must exist and be locked (bold, with a lock icon). If it is not locked, config.js is not being read.
2. Check the file locations against Installation → by hand: config.js next to the browser binary, config-prefs.js in defaults/pref/, and the utils unpacked directly into <profile>/chrome/utils/.
3. Restart the browser fully (quit it, do not just close the window).

The preferences are not locked

config.js is loaded by Firefox's AutoConfig mechanism, which only runs when the enabling preferences are in defaults/pref/. Check, in order:

1. config-prefs.js is in <FIREFOX ROOT>/defaults/pref/: the file name and the .js extension matter, and this directory is the one Firefox itself reads preferences from.

2. The contents are exactly:

   pref("general.config.obscure_value", 0);
   pref("general.config.filename", "config.js");
   pref("general.config.sandbox_enabled", false);

3. config.js is next to the browser binary, and starts with the // skip 1st line comment (AutoConfig ignores the first line, so the preferences on the second line are the first statements that execute).

Details: Configuration files (config.js).

The scripts were working and now they are not

A browser update is the usual cause: either it broke a legacy add-on, or it invalidated the startup cache.

1. Open the updater from the browser menu and install any available update.
2. In about:support, click Clear startup cache….
3. Restart the browser.

If the updater tab itself will not open, install by hand from the Download page.

My .uc.js script does not run

1. Is the file in the profile's chrome/ directory (not chrome/utils/, and not in a subfolder)? The loader scans the top level only.
2. Does the extension end in .uc.js?
3. Is the header block complete (// ==UserScript== … // ==/UserScript==)?
4. Does @include match the window you are testing in? With no @include, the script runs only in the browser window.
5. Is the file listed in the userChromeJS.scriptsDisabled preference?
6. Clear the startup cache (about:support → Clear startup cache…) after every edit.

For a working example, read restart.uc.js in the repository, and see Writing your own .uc.js for how to read the loader's own state from the Browser Console.

An update is offered every day and I want to stay on the current version

Use the updater tab's own choices, explained in Installer and auto-updater: Remind me Tomorrow to skip that day, or Don't show again for this update to permanently skip that package. Both are per-package, and can be reverted by clearing the skip preference in about:config (extensions.firefox-scripts.skippedHash.<package>).

The installer does not see my browser

Detection needs a running browser: it inspects running processes and lock files. Start the browser first, then run the installer.

If the browser runs from an unusual location (a portable build, an extracted archive), install by hand instead. Installation → by hand uses the paths from about:support, so it works regardless of where the browser lives.

The installer tab shows a network error

The installer performs no network I/O of its own. The tab it opens is the component that downloads the packages. A network error banner means that tab could not reach the release host. Check for a proxy, an extension blocking requests, or a firewall rule for the browser, and try again.

Windows: the installer will not start

• SmartScreen shows "Windows protected your PC" → More info → Run anyway.
• A UAC prompt appears → approve it: it is one elevation for the copy into the installation directory, performed by a checksum-verified helper.
• The file may have been blocked after download → right-click → Properties → Unblock.

Getting help

Collect this before opening an issue:

• browser name and version (about:support → Application Basics),
• the Profile Folder and Application Binary paths,
• whether the preferences in about:config are locked,
• any error text from the Browser Console.

A quick diagnostic

about:support → Extensions lists the legacy add-ons the loader found. If TabMixPlus is not listed there, the loader did not run. Go back to the first two sections.