Extension compatibility and known limitations
Install most standards-based Chrome Web Store extensions, Firefox Add-ons, and Safari Web Extensions on Mac. Compatibility varies where an extension depends on a browser-specific API, a native companion, or an Apple-managed capability.
Start with the full extension and API compatibility matrix for current Bitwarden, LastPass, Dark Reader, uBlock Origin, runtime-type, and namespace-level results. This page explains the platform boundaries behind those statuses.
Extension installation, actions, options, shortcuts, and management are currently available in Crest for Mac. Installations and settings remain per Space and per device.
Crest measures package verification, installation, and runtime startup separately from complete workflow support. A package can load cleanly while an optional feature still needs an API WebKit does not implement.
What Crest supports
- A native permission and compatibility review for signed CRX3 packages from the Chrome Web Store, and for Mozilla-signed add-ons from Firefox Add-ons.
- Per-Space and per-device installation, storage, enablement, permissions, website access, and pinning.
- WebExtension action popups, options pages, and keyboard commands where their APIs are available in WebKit.
- Plain-language Running, Limited compatibility, Needs attention, Off, and blocked states, with JavaScript errors collapsed under Technical Details.
- Known package-specific limits in the pre-install review, the orange post-install result, and the persistent Settings row.
- Load Unpacked… for development and manual testing, without native-messaging access.
- Discovery of ordinary WebExtension resources inside signed Safari apps, without treating Safari native handlers as portable.
- Automatic signed updates for enabled Chrome Web Store installations. Firefox Add-ons can be refreshed from their listing and are verified again before replacement.
See Direct build, App Store, and native companions for the distribution boundary.
Signed-package audit
Validated through August 30, 2026:
| Extension | Version | Startup result | Measured boundary |
|---|---|---|---|
| Dark Reader | 4.9.129 | Loads cleanly | No startup error observed. |
| uBlock Origin Lite | 2026.804.1652 | Loads cleanly | Declarative Net Request package loaded without a startup error. |
| 1Password | 8.12.30.21 | Production-signature gated | Setup, sign-in navigation, BrowserSupport launch, persistent messaging, and browser authorization were verified. The Apple Development build was rejected as BrowserSignatureInvalid; Developer ID pairing and autofill remain. |
| SponsorBlock | 6.1.6 | Loads cleanly | No manifest or startup runtime error observed. |
| Bitwarden | 2026.8.0 | Verified end to end | Device verification, login, vault, relaunch unlock, native popout, page injector, and autofill were verified directly. |
| LastPass | 4.155.1 | Verified end to end | Login, vault, relaunch persistence, matching-item popup, in-field integration, and autofill were verified directly. |
| Grammarly | 14.1319.0 | Partial / experimental | Managed storage, cookie, and telemetry limits are reported. |
| React Developer Tools | 7.0.1 | Partial / experimental | Isolated execution world is unsupported. |
| Tampermonkey | 5.5.0 | Partial / experimental | WebKit rejects tabs.onUpdated startup registration. |
| iCloud Passwords | 3.3.0 | Apple entitlement pending | The worker loads with exact-package compatibility shims, but Apple's password helper rejects browsers without its managed Web Browser Public Key Credential entitlement. Pairing and autofill are blocked in the current build. |
“Loads cleanly” covers verification, installation, WebKit context load, and initial background startup. It does not certify every site, account, popup, update, native-companion authorization, or optional feature.
Firefox add-on audit
Validated on August 13, 2026. Crest verifies each add-on against the checksum, size, and identity Mozilla published for that exact version before installing it.
| Extension | Version | Startup result | Measured boundary |
|---|---|---|---|
| Dark Reader | 4.9.129 | Loads cleanly | No manifest or runtime error observed, and no unsupported API reported. |
| uBlock Origin | 1.73.0 | Partial / engine limited | The MV2 background page, popup controls and statistics, page integration, and child-frame classification work. WebKit does not consume blocking webRequest listener responses, so full request cancellation, redirect, header mutation, and authentication parity remain unavailable. |
| Bitwarden | 2026.7.0 | Partial / experimental | The package and core worker load. Notification-click handling is unsupported. The Firefox build does not request a native companion, so it is not blocked before installation. |
Sidebars, container tabs, extension themes, and blocking webRequest are expected gaps for every Firefox add-on. See Install from Firefox Add-ons.
1Password's measured boundary
The Chrome Web Store package installed as Running, rendered its setup interface, opened my.1password.com in a normal Crest tab, and caused Crest for Mac to launch /Applications/1Password.app/Contents/MacOS/1Password-BrowserSupport.
Crest completed 1Password's additional-browser authorization UI and traced the extension's first account request. The helper rejected the Apple Development signature as BrowserSignatureInvalid. The Developer ID signed and notarized Crest release is required for the next pairing and autofill test. Follow Set up 1Password in Crest.
iCloud Passwords' measured boundary
iCloud Passwords installs and its worker starts after exact-package WebKit compatibility shims. Its native helper is separately protected by Apple: the current Crest signature does not carry the managed browser credential entitlement, so the popup cannot pair and Password AutoFill does not work. Crest has requested the capability. See iCloud Passwords in Crest.
Safari-only formats
Safari content blockers and legacy Safari App Extensions are not WebExtensions and are not supported.
wBlock
wBlock is a hybrid. Its toolbar and userscript portion use Safari Web Extensions, but its primary blocker uses five Safari-only content-blocker extensions. Crest cannot reproduce the core wBlock blocking behavior and does not market wBlock as fully supported.
If an installed extension reports an error or a feature does not respond, continue with Troubleshoot partial compatibility.