What Is Firefox and How Do You Use It?

Firefox is a free, open-source web browser you can install on Windows, macOS, Linux, Android, and iOS. It is developed by Mozilla and is best known for its privacy protections, tab management, and support for add-ons. Use it if you want a browser you can customize heavily, sync across devices, and inspect or modify at the source-code level. The steps below cover installing it, setting it as your default, adding extensions, and fixing the most common problems.

What Firefox Is and Who Makes It

Firefox is a browser built and maintained by Mozilla, a organization that develops open-source software. Because its source code is publicly available, anyone can review how it works, report bugs, or contribute improvements — the same open-source model described by communities like MyBrowserAddon, which hosts documentation, tutorials, and bug-report forms for free browser-based projects.

That openness matters for two practical reasons:

Transparency: you or a security researcher can inspect the code rather than trusting a closed binary.
Choice: independent developers can build add-ons, forks, and alternative implementations on top of it.

Firefox is not the only browser, and it is not automatically the right pick for everyone. If you rely on a specific site or internal tool that only supports another browser, that constraint should decide your choice before any feature comparison does.

Key Features You Will Actually Use

Feature	What it does	When it helps
Tab management	Handles many open tabs, with grouping and pinning	Research sessions, dozens of open pages
Privacy protections	Blocks known trackers and third-party cookies by default	Everyday browsing on ad-heavy sites
Sync	Shares bookmarks, history, passwords, and open tabs across signed-in devices	Moving between desktop and phone
Add-ons	Installs extensions from the official add-ons site	Ad blocking, password managers, developer tools
Open source	Source code is public and modifiable	Users who want to verify or customize behavior

Privacy protections reduce tracking but do not make you anonymous. They are a default, not a guarantee, and some sites may break until you adjust the protection level for that site.

How to Install Firefox

On desktop (Windows, macOS, Linux)

Go to the official Mozilla website and download the installer for your operating system.
Run the installer and follow the prompts. On Linux you can also install it through your distribution's package manager.
Open Firefox. On first launch it offers to import bookmarks and settings from another browser — accept if you want your existing data carried over.
Sign in to a Mozilla account if you want Sync. This is optional; the browser works fully without it.

Expected result: Firefox opens to a start page, and your imported bookmarks appear in the bookmarks menu.

On mobile (Android, iOS)

Install Firefox from the Google Play Store or the Apple App Store.
Open the app and optionally sign in with the same Mozilla account you used on desktop.
If you signed in, your synced tabs and bookmarks appear within a few moments.

Setting Firefox as your default browser

Windows: Settings → Apps → Default apps → choose Firefox.
macOS: System Settings → Desktop & Dock → Default web browser → choose Firefox.
Android: Settings → Apps → Default apps → Browser app → choose Firefox.
iOS: Settings → Firefox → Default Browser App → choose Firefox.

Menu names shift between operating-system versions, so if a path does not match, search your system settings for "default browser."

How to Find and Install Add-ons

Open the official Firefox add-ons site (addons.mozilla.org) or go to the Add-ons manager inside the browser.
Search for the extension by name.
Check the developer, the number of users, the rating, and the permissions the extension requests before installing.
Click Add to Firefox, then confirm the permissions prompt.

Expected result: the extension's icon appears in the toolbar, and it is listed in the Add-ons manager where you can disable or remove it.

Install only from the official add-ons site or a source you trust. An extension that asks for permission to read data on all websites can see everything you do in the browser, so match the permissions to what the extension is supposed to do. If you are unsure whether a plugin or extension is safe, treat the permission list as the deciding factor.

Common Problems and Fixes

Pages load slowly or the browser feels sluggish

Close unused tabs, or use the browser's task manager to find the tab consuming the most memory.
Disable extensions one at a time to identify a heavy one.
Clear the cache if a specific site keeps loading stale content.

A page will not load at all

Try the page in a private window. If it works there, an extension or cached data is the likely cause.
Turn off tracking protection for that specific site if the site depends on blocked scripts.
Check whether the site requires a browser or plugin you do not have.

Sync is not updating

Confirm you are signed in with the same account on both devices.
Check that Sync is enabled for the specific data types you expect (bookmarks, tabs, passwords).
Sign out and back in if changes still do not appear.

An extension stopped working

Check the Add-ons manager for a pending update.
Confirm the extension is still compatible with your browser version; some are abandoned by their developers.

Who Should Use Firefox

Choose Firefox if you want an open-source browser with strong default privacy protections, deep add-on customization, and cross-device sync. Consider a different browser if a site or tool you depend on only supports another engine, or if you need a feature that Firefox does not offer. The open-source model means you can verify how it works and contribute fixes — but it also means support for any given add-on depends on its individual developer, not on Mozilla.