Key Highlights

• Firefox 149 introduces a native Split View feature for side-by-side browsing in one tab
• Mozilla improves Linux, Windows, and macOS integration with performance and UI upgrades
• New privacy, security, and developer-focused features arrive ahead of the March 24 release
• Firefox 149 rolls out a free VPN and major web standards support updates

Mozilla has released the final builds of the Firefox 149 Web Browser, making the update available for download ahead of its official launch on March 24, 2026. With this release, Mozilla delivers new productivity tools, stronger security controls, and broader platform integration.

More importantly, Firefox 149 focuses on practical improvements. It enhances everyday browsing, boosts performance across devices, and expands support for modern web standards.

What Is New in Firefox 149 Web Browser?

Firefox 149 arrives as a feature-rich update that targets both regular users and developers.

This version introduces Split View browsing, refreshes key interface areas, improves privacy protections, and tightens performance under real-world network conditions. At the same time, Mozilla continues to align Firefox with evolving operating system standards.

How Does Split View Work in Firefox 149?

Split View stands out as the most anticipated feature in Firefox 149 Web Browser.

Users can now open two web pages side-by-side within a single tab. To enable it, users simply right-click a tab or add a split view to a tab group. As a result, comparing content, multitasking, and research workflows become easier.

Unlike extension-based solutions, Firefox builds Split View directly into the browser. Therefore, users experience smoother performance and better stability.

What Interface and Settings Changes Are Included?

Mozilla also refines Firefox’s interface in this release.

Firefox 149 adds a new Profiles section under General Settings, allowing users to manage separate browsing environments more easily. Meanwhile, Mozilla redesigns the Browser Layout and renames Network Settings to Proxy Settings for better clarity.

In addition, the built-in spell-checking feature now makes dictionary management simpler. Consequently, users can customize language support faster without digging through menus.

How Does Firefox 149 Improve Desktop Integration?

Firefox 149 Web Browser strengthens integration across major operating systems.

On Linux, Firefox now defaults to the XDG portal file picker. As a result, file selection works more consistently across desktop environments. On Windows, Mozilla enables the WebRender layer compositor by default, which reduces power usage during full-screen video playback and improves WebGL and WebGPU performance.

Meanwhile, users on macOS and Windows can add a Share button directly to the toolbar. This change allows faster sharing of tabs through native system options.

What Performance and Media Improvements Are Included?

Mozilla also targets performance improvements throughout Firefox 149.

The browser now handles HTTP/3 uploads more reliably on unstable networks. In addition, Firefox loads PDFs faster and lets users download images directly from PDF files using the context menu.

On Android, Firefox 149 supports closing popovers and dialogs using the Back Button. As a result, navigation feels more intuitive on mobile devices.

What New Security and Privacy Features Are Added?

Security remains a central focus in the new browser.

Firefox can now automatically block notifications and permanently revoke permissions for websites flagged as malicious by SafeBrowsing. At the same time, Mozilla tightens requirements for JavaScript files that run in the parent process, reducing exposure to potential attacks.

Additionally, Firefox refreshes its error pages with updated visuals. Mozilla also merges privacy and security indicators into a single TrustPanel, which makes it easier to review page-level protections at a glance.

What’s New for Web Developers?

Firefox 149 introduces several changes aimed at web developers.

The Storage Inspector now includes a toolbar button that deletes all entries of the selected storage. Developers can also jump directly to computed CSS values from the Rules view. Furthermore, Firefox adds support for the HTML attribute popover="hint" and enables the spec-compliant HTMLMediaElement.captureStream() API.

Beyond that, the update supports media pseudo-classes such as :playing and :paused, new CSS shape functions, MathML font improvements, and a new Reporting API for web applications.

When Is Firefox 149 Officially Launching?

Mozilla plans to officially unveil Firefox 149 on March 24, 2026, alongside Firefox 140.9 and Firefox 115.34.0 ESR. However, users can already download source tarballs and binaries for 64-bit, 32-bit, and ARM64 systems from Mozilla’s FTP servers.

Overall, the new release continues Mozilla’s push toward better performance, stronger security, and modern browsing experiences across platforms.