Sidebery manages Firefox tabs and bookmarks in a sidebar through a browser extension.
Open source
24 alternativesSine
Sine manages themes for Firefox-based browsers, according to its project description.
About Sine
Sine is an open-source mod and theme manager for Firefox-based browsers. It injects itself into the browser settings page, where a built-in marketplace lets users browse and install Sine-compatible mods; mods can also be installed from the project's website. Developers publish mods by opening an issue from a template, and Sine pulls updates directly from the mod's repository so users do not have to be told to update. Unpublished mods with a valid format can be added by entering the repository name. Installation is handled by automatic installers for macOS, Linux, and Windows on both x64 and ARM CPUs, with a manual guide in the documentation. Pricing is not stated in the repository.
Key features
- Built-in marketplace inside the browser settings page
- Mod installation from the project website as well
- Updates pulled directly from each mod's repository
- Per-mod update toggle and auto-update on browser start
- Supports userChrome, userContent, Zen chrome format, metadata-less mods
- Automatic installers for macOS, Linux, Windows on x64 and ARM
Best for: Users of Firefox-based browsers who want to install and manage community mods and themes without manual setup.
Good for
- Open-source repository with installation documentation
- Compatibility with several mod formats, including userChrome, userContent and Zen chrome
- Automatic installers cover macOS, Linux and Windows on x64 and ARM
Watch out for
- macOS installation requires terminal commands to unquarantine and codesign the installer
- A browser restart is needed to complete setup
- No pricing information is published in the repository
Sine at a glance
- Website
- github.com/CosmoCreeper/Sine
- Category
- Software & Utilities › Firefox Extensions
- Type
- Open-source project
- Pricing
- Not confirmed. Check the site
- Open source
- Yes · Source code
- Language
- English
- Last checked
- Oct 6, 2026 · Online when checked
- Listed
- Oct 5, 2026
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Sine FAQ
How is Sine installed?
Automatic installers are provided for macOS, Linux and Windows on x64 and ARM, with a manual installation guide in the documentation. On macOS the downloaded file must be unquarantined and codesigned via terminal before running.
How do mods receive updates?
Sine pulls updates straight from each mod's repository rather than requiring update requests. Updating can be turned on or off for individual mods, and auto-updating on browser start is available.
Can mods be installed outside the built-in marketplace?
Yes. Sine supports installing mods from the project website, and unpublished mods with a valid format can be added by typing the repository name.
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