Updated: 25 October 2026. Does normal Firefox work while a web app installed through PWAsForFirefox crashes on launch? A specific compatibility problem is documented for Firefox 158. This guide helps individuals and small IT teams identify that case without prematurely deleting profiles or local app data. [1][2]
What is confirmed, and what is not?
The third-party project released version 2.20.1 on 9 October 2026 to address launch crashes with Firefox 158. Mozilla recommends updating to 2.20.1 or later. Bug 2077967 describes a JavaScript module-loading problem, so an incomplete-installation message does not automatically establish a faulty disk. This advice does not cover every Firefox startup failure. [1][2][3] PWAsForFirefox combines an extension, a native program and its own modified Firefox runtime. App profiles are separate from the normal browser profile. Updating only the main browser, or backing up only its profile, is therefore insufficient as a repair or data-protection measure. [4][5] Important for the current status: the tracker now marks Firefox 158 as fixed; maintainer comments confirm that this particular issue is resolved in 158.0.1. Not every current 158 installation is therefore affected. Check the runtime actually used by the app as well as the project version, and use a current approved maintenance release. The older release note remains useful for historical diagnosis but does not replace this version distinction. [3]
Prepare: protect app data and establish responsibility
Record the operating system, main browser version, PWAsForFirefox extension and native program versions, and affected apps. Establish whether the runtime is managed or manually customized; on work devices, changes belong to the responsible IT team. Save open work. Before repair, close all apps and back up the affected app profiles and associated configuration using the approved procedure. Treat backups as confidential because they may contain sign-in data. Being signed into the normal browser does not prove that unsaved or local-only app data is backed up.
Five steps for safe diagnosis
- Identify the symptom: launch the affected app once and record its message. Then open its known website directly in the normal browser without bypassing security warnings. If the website works but the standalone app exits with an incomplete-installation message, the documented case is plausible. This does not prove the cause; network, account and website problems need separate investigation.
- Check the project version: use the existing official installation or package-management route to update PWAsForFirefox to at least 2.20.1, or a newer approved version. Check the extension and native program separately; an updated extension does not prove the native package was updated. Retry the existing app shortcut. Do not add a parallel installation, downgrade Firefox or bypass organizational policies. [2][4]
- Address the runtime only if the failure persists: in PWAsForFirefox extension settings, select “Reinstall runtime”. This replaces the dedicated runtime with a current Mozilla download, including any manually customized runtime. Project documentation says it does not remove the main browser, profiles or data; a backup is still a prerequisite. Automatic reinstallation is not supported on every platform. If the feature is unavailable or the installation is customized, stop here and involve the package maintainer. [1][5]
- Then run “Patch profiles and runtime”: this applies the currently installed project patches to the runtime and profiles. Mozilla specifies reinstalling the runtime first and patching afterwards. Do not substitute “Update web apps”: that separate operation also reloads app manifests and is not an equivalent runtime repair. Launch the same existing app afterwards rather than installing another instance over it. [1][5]
- Accept the result using harmless data: check startup, expected account, existing local content and a typical permitted workflow. Close the app cleanly and launch it again. Do not use a real purchase, message or production-data change as a test. Record versions and outcome; an open window alone proves neither data completeness nor working synchronization.
Verify success and stop if problems remain
If startup still fails, do not repeat repair indefinitely. Collect the message, time and versions for IT or project support; do not publish profiles, cookies or complete unreviewed logs. Stop immediately if data is missing or a new problem appears, and preserve the backup unchanged. Restoration needs an agreed recovery procedure with a compatible program version, not a blanket overwrite of the active profile. The approved website in a normal browser may provide a temporary alternative after checking the account, required features and data availability. Local changes that have not synchronized may be absent there.
Context and sources
Source-based troubleshooting, not a PWAsForFirefox test performed here. The backup and acceptance sequence is editorial guidance, not a universal platform guarantee. The topic is based on documented vendor and project information, not a claimed search trend. Free software, no purchasing recommendation and no affiliate links.