Thought your older Intel Macs running on Lion all the way up through Mojave could no longer have a modern, functional web browser? Named after the “red leaves of autumn” in Japanese and based off of FireFox 140 ESR from June 2025, it’s quite an upgrade.
It is a fork/successor to the FireFox-dynasty project, bringing fully up-to-date web browsing/services, combined with newer security patches unsupported by Apple or Mozilla.
Setting it up
The latest version of Momiji is compiled for several different versions of macOS, so you must download the version which correlates to what you’re running on your Mac. You may download it here or visit the GitHub page.
From our Software Repository:
- OS X Lion 10.7 – Mavericks 10.9: Momiji-Lion.zip (Download, 89.8 MB)
- OS X Yosemite 10.10 – El Capitan 10.11: Momiji-Yosemite.zip (Download, 86.4 MB)
- macOS Sierra 10.12 – Mojave 10.14: Momiji-SierraMojave.zip (Download, 82.6 MB)
From the GitHub page:
What you need to know
- FireFox 140 ESR baseline ends on September 15th, 2026 according to the FireFox release calendar. After this date, new versions of Momiji will be based off of FireFox 153 ESR.
.- There is a new nightly build of Momiji based off the 153 ESR, but it requires a Core 2 Penryn CPU/SSE 4.1 or newer, as well as OS X Mountain Lion and up.
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- There is a new nightly build of Momiji based off the 153 ESR, but it requires a Core 2 Penryn CPU/SSE 4.1 or newer, as well as OS X Mountain Lion and up.
- Graphical Hardware Acceleration may be buggy on some Macs. Fonts may not work correctly in 10.7 and 10.8.
. - DRM-encrypted content (e.g. Spotify, Netflix) does not play by default, and requires a new plugin due to an old unsupported one.
. - Full screen sharing (in Google Meet, Microsoft Teams, etc.) and Translations is unavailable on macOS 10.7.
. - Passkeys may not work as they should (in my own experience)
. - Discord voice, video calls and its Go Live streams are unsupported as they require at least Firefox 142
. - Security Vulnerabilities fixed in Firefox ESR 140.12 – www.mozilla.org
. - Firefox 140 Release Notes – www.firefox.com
My experience so far
This browser is simply remarkable. While there are bugs here and there, it’s remained rather stable, steady, and more importantly, dependable. Using this browser on a Mac running OS X El Capitan makes it feel like you can live on this Mac. YouTube, Social Media, Shopping, etc; and mostly all websites play nice, but where it mattered to me was being able to really use it to not only write this article, but also manage the site.
Since my Mac is on OS X El Capitan, theming the OS becomes more difficult than in Yosemite. OS X 10.11 introduces a dark Menu Bar + Dock, but not a system-wide theme. I’ve always wanted to find a robust way of adding a “Dark Mode” to El Capitan, as it would give my Mac Pro 2,1 a more modern appearance. Momiji allows many themes, but can also bring 10.11 one step closer to feeling like Mojave.
Now instead of just having a classic Mac Pro full of apps parked next to an M4 Mac Mini, it feels more like a choice to use one or the other.