Mozilla shipped Firefox 153 on July 21–24, 2026, alongside the concurrent 153 ESR build. It's a feature-dense release — the kind that usually marks a new direction rather than routine maintenance. The headline items are a rebuilt profile management system, a native split-view mode, and on-device AI capabilities for enterprise deployments.
Profiles, finally done right
Firefox has had profile support for years, but it was always a power-user feature buried in about:profiles and not integrated into normal browser use. Firefox 153 changes that. The new profile management system gives each profile its own tabs, bookmarks, history, passwords, and extensions — all visible and switchable from the main UI. This mirrors what Chrome has offered for years and what Safari added more recently. For users who want to separate work, personal, and side-project browsing without running multiple browser windows, this is a meaningful quality-of-life upgrade.
Split view and HDR
The split-view feature lets you tile two web pages side by side in a single window — a surprisingly long-requested feature that third-party extensions have been providing for years. Mozilla's release notes don't specify keyboard shortcuts yet (they're listed in the release candidate documentation), but the feature is tab-based: you select a tab and choose to split it against another open tab.
HDR video playback arrives on Windows 153, which brings Firefox in line with Chrome and Edge for high-dynamic-range content on compatible displays. For users with HDR monitors who have been watching HDR content in a non-HDR browser, this one will be immediately noticeable on the right hardware.
On-device AI and PDF improvements
The enterprise-focused on-device AI features let organizations deploy Firefox with a local AI model for tasks like text summarization and composition — without routing data to external servers. Mozilla has been careful to frame this as an opt-in, organizationally controlled feature rather than a default consumer toggle.
On the PDF side, Firefox 153 adds the ability to merge multiple PDFs and insert images directly into PDF documents from within the built-in PDF viewer. These were common reasons users reached for external tools, and folding them into the browser removes one more reason to leave.
The two-week release cadence shift
Perhaps the most structurally significant announcement bundled with this release: starting September 2026, Firefox will move to a two-week release cadence, down from the current four-week cycle. Mozilla frames this as a response to the pace of web platform development — new CSS features, browser APIs, and security patches are moving faster than a monthly cadence can comfortably track. The ESR channel will remain on its longer cycle for enterprise deployments that need stability over freshness.
Firefox 153 is available now via the standard update mechanism.