Firefox 151 is now available for Windows, macOS, Linux, and Android, bringing a mix of privacy upgrades, PDF tools, VPN improvements, and security fixes. The update also arrives for Firefox ESR versions, which is important for people and organizations that stay on long term support releases instead of moving to every main Firefox version.
The biggest security point is that Firefox 151 fixes more than 30 vulnerabilities. Mozilla’s advisory lists four externally reported flaws as high risk, including one issue that could allow a possible escape from the browser sandbox. Eleven more vulnerabilities are rated medium risk, while the rest are considered low risk. Mozilla also fixed internally discovered memory management problems, which are often important because they can lead to crashes or possible exploitation if left unresolved.
Firefox 151 improves private browsing and adds a useful PDF merge tool
The privacy improvements are one of the main reasons to install this release. Firefox 151 adds stronger tracking protection that Mozilla says can reduce the number of people advertisers can identify through common fingerprinting methods by 14 percent overall. On macOS, the reduction can be as high as 50 percent. Fingerprinting is harder to notice than cookies because it uses details about your browser, device, and system to recognize you across websites.
Private browsing also gets a small but useful change. You can now clear an entire private session with one button click without closing the browser window. This starts a fresh private session with no history, which is more convenient if you want to reset your private browsing activity quickly.
| Firefox 151 change | What it means |
|---|---|
| More than 30 security fixes | Reduces risk from browser vulnerabilities |
| Stronger fingerprinting protection | Makes tracking harder for advertisers |
| One click private session clearing | Resets private browsing without closing the window |
| PDF merging | Combines multiple PDF files inside Firefox |
| VPN location selection | Adds supported location choices in selected countries |
| Linux profile backup | Allows local profile backup and cross platform restore |
Firefox’s built in PDF viewer and editor also gains a practical new feature. It can now merge several PDF files into one document. That makes Firefox more useful for simple document work because you do not need a separate app just to combine PDFs.
Mozilla is also expanding the free VPN feature that was introduced in Firefox 149. Firefox 151 adds location choices for supported regions, including the US, Canada, the UK, France, and Germany. The VPN feature requires a free Mozilla account and includes 50GB of monthly VPN traffic. The location selection is rolling out gradually, so it may not appear for everyone at the same time.
The New Tab page has also been refreshed with more background images and is being prepared for additional features ahead of Firefox 152, which is expected on June 16. The translation page, found at about:translations, can now be opened through the menu under More Tools. Linux users also get the option to back up Firefox profiles locally and restore them across platforms.
Firefox ESR 140.11.0 and 115.36.0 are also available. Firefox ESR 115 remains available for older systems such as Windows 7, Windows 8.1, and macOS 10.12 to 10.14, with security updates planned until August 2026. Thunderbird updates based on the same Firefox codebase are also expected, with security fixes inherited from the browser.
For most people, Firefox 151 is worth installing as soon as it appears. It improves privacy, adds a genuinely useful PDF feature, and fixes several security issues that could matter in daily browsing.
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