Name the extension’s job

Write down the extension name and version, Firefox’s running version, the intended action, the website or harmless example, and whether the window is private. Use the developer’s instructions to define what should happen. “Installed” only describes one part of that task.

If the website itself fails even without the extension, start with the one-site guide. This guide follows the extension’s own function.

Check installed and enabled state

Open about:addons and choose Extensions. Find the named extension and read its status and any error. If absent, use Mozilla’s installation-error guidance for the exact message. If disabled, establish whether you intentionally disabled it or Firefox reports a compatibility, verification or blocking condition.

For an ordinary extension you trust that you intentionally disabled, enable it and retry its documented function. Keep notes before reinstalling: removal can affect extension-specific settings. A toolbar icon alone does not verify that the task works.

If it works normally but not in a private window

Firefox requires permission for eligible extensions to run in private windows; some extensions cannot be allowed there. In the extension’s details, check Run in Private Windows. Grant access only if you want that extension to access the private context, then repeat its intended action. Extensions in Private Browsing

Bitwarden documents this private-window permission for its own Firefox extension. That is a developer-documented example of a condition to check, not a hands-on test of a password manager or a recommendation to change access for every extension. Bitwarden: Firefox private windows

Match access to the documented task

For Manifest V3 website-access notifications, open the extensions toolbar panel, find the named extension’s notification and use its menu to review access. Mozilla documents this condition separately from private-window permission. Compare the request with the developer’s explanation, grant only intended access, and retry. Manage extensions with the toolbar button

Use harmless data when testing. A page, account state, private window or unsupported feature can change the outcome. Avoid a blanket “allow everything” fix; the useful question is which documented condition the intended function needs.

Treat verification and blocking messages separately

Use Firefox’s exact message and the current developer or Mozilla instructions. Add-on signing in Firefox explains signature verification. Look for a legitimate supported update from the developer or Mozilla’s add-on listing. Do not switch off verification, bypass a block, or download arbitrary older packages as a troubleshooting shortcut.

If the supported task still fails

Check the developer’s supported Firefox versions and relevant issue or release notes. A reported fix needs a matching shipped extension version before it answers your case. If another extension may interfere, make one reversible comparison and restore changes that did not help. Troubleshoot extensions and themes

Troubleshoot Mode disables extensions, so it cannot demonstrate that the extension itself performs its function in that mode. Use the method comparison to interpret what such a test can establish.

Finish with the function, or a useful report

Success means the intended action works in the recorded supported context. Check it again after restoring unrelated test changes. If unresolved, record the exact extension and Firefox versions, enabled state, window context, expected action, one change, retest result and reversal. Share that minimal record with the developer’s support channel; omit private account data.

The support-record tool can capture a sequence of comparisons. A generated record is a handoff, not evidence that the problem is fixed.

What was verified for this guide

The linked Mozilla and Bitwarden documentation was checked on 8 October 2026. This guide does not report a new graphical Firefox experiment, a real extension defect, measured recurrence or search demand. The existing synthetic extension example on the website guide tests a different task: a page deliberately broken by a temporary test extension.

Sources & scope

Source checks are dated individually below. Interface labels and availability may vary by version and platform. This guide is based on checked product documentation.

Source review: Firefox Updates Verification Desk, an automated editorial role. Read the AI and verification disclosure.