Just a couple weeks ago, aobaharuki2005 dropped the latest versions of Momiji web browser on GitHub, including an updated Momiji v140.16 (stable version) as well as a rolling build based off of the latest version of FireFox 156.0 – a browser which is also only a few weeks old.

Featuring some recent security fixes, this Core 2 Duo-targeted (Conroe/Merom) 64-Bit browser gifts OS X Lion through macOS Mojave a completely up-to-date, September 2026 browser. This means every OS in this range, including Mountain Lion, Mavericks, Yosemite, El Capitan, Sierra, and High Sierra.

While this is newer version is still a rolling (less stable) build, using this browser in El Capitan over the older FireFox 140.12 is already showing performance improvements, making this 20 year-old Mac feel very usable again. Daily drivable, even!

• See original article: Momiji: A new FireFox browser for OS X Lion – Mojave

On Your Mac

Momiji is available on GitHub and is compiled for two major branches/builds: the Lion thru El Cap version, and the Sierra thru Mojave version. Both have the v140.16 and the new cutting-edge v156.0, so if you still have a 64-Bit Intel Mac from the beginning of the Intel transition.. you’re in luck. All you need is a Core 2 Duo CPU – Core Duo CPUs won’t work as they’re 32-Bit.

1. Download the browser

• GitHub page: https://github.com/aobaharuki2005/momiji-web-browser/releases/tag/stub-v156.0-v140.16.0esr
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• v156.0 for: Sierra, High Sierra and Mojave
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• v156.0 for: Lion, Mountain Lion, Mavericks, Yosemite, and OS X El Capitan
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• v140.16.0 (Stable) for: Sierra, High Sierra, and Mojave
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• v140.16.0 (Stable) for: Lion, Mountain Lion, Mavericks, Yosemite, and OS X El Capitan

2. Place in Applications folder

If you’re swapping out Momiji or any later FireFox for Momiji-Rolling, changing the app name to just “Momiji” preserves app settings, bookmarks, etc;

My experience so far

Since the middle of summer I’ve been daily-driving 140.12 on my own Mac Pro 2,1, and it’s completely changed my perspective of using this Mac in 2026 by bringing modern web browsing back to it.

Now built off an even newer version of FireFox, this latest iteration of Momiji makes early intel-era Mac web browsing feel next level! Graphical elements such as buttons, tabs, dragging windows, going full screen, etc; and those sort of basic functions feel significantly improved.

While Momiji 156.0 may get only a 4.29 on Speedometer 3.1, this number doesn’t accurately illustrate using the browser on a day-to-day on a well configured Core 2 Duo Mac – it looks better in a video.

When my mouse hovers over a tab there’s no delay for the preview, tabs open much quicker, browser animations don’t hang or freeze like they used to, and overall web pages render much faster than before. Moreover, it seems this browser can better handle having many tabs open at once.

What’s new in Momiji since our last article?

Both the new 140 and 156 versions have near-identical, up-to-date, 2026 security updates which come along with FireFox, as well as bug fixes specific to Momiji.

• Security Vulnerabilities fixed in Firefox ESR 140.16
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• Security Vulnerabilities fixed in Firefox 156
• For 140.x:
  • 140.13: security fixes + restored “Set Momiji as default browser”
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  • 140.14: primarily another Firefox ESR security-update rollup.
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  • 140.16: current/final-ish 140 ESR branch, with another security rollup, a real Momiji-specific WhatsApp Web crash fix, and simplified release builds.
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• What’s new in 156?
  • Thanks to the work done by Jazzzny in backporting FireFox 153 ESR, newer versions of Momiji based on the latest FireFox are possible. Right now you can run the latest FireFox Gecko on any Mac running Mac OS X Lion all the way through macOS 10.14 Mojave, and the browser is literally built for Merom/Clovertown-era Early Core 2 Duo Intel Macs!
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  • Same AppleVTEncoder/WhatsApp Web fix as 140.16
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  • Browser now reports 10.15 instead of the actual OS X version.
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  • September 2026 browser security fixes

My thoughts

Thank you so much to everyone involved in this project, for continuously working on a new browser for our aging Macs, so the community can get the most out of their Apple gear. Words don’t describe what it’s like to see a modern, responsive and compatible web browser on this Mac Pro 2,1 – it brings the whole thing together, web browsing and apps included. Suddenly, a DDR2-era Clovertown Xeon Mac feels new again.