For users running macOS 10.10.5 (Yosemite), the most recent and final compatible version of Firefox is Firefox 78.15.0 ESR (Extended Support Release). This version reached its final update on October 5, 2021, and is no longer receiving security patches from Mozilla. Download Instructions

Because standard download pages automatically offer the newest version (which requires macOS 10.15 or later), you must access Mozilla’s archives directly to find the compatible file:

Official Mozilla Archive: You can download the English (US) installer directly from the Mozilla CDN. File Name: Firefox 78.15.0esr.dmg

Other Languages: If you need a different language, navigate to the main directory and select your preferred regional folder. Installation Steps Download the .dmg file from the link above.

Open the file and drag the Firefox icon into your Applications folder.

Launch Firefox. If you previously used a newer version of Firefox on a different OS, you may be prompted to create a new profile because version 78 cannot read data from newer versions (like Firefox 130+). Critical Security & Compatibility Notes

End of Support: Version 78.15.0 ESR has not received security updates since October 2021. Using it for sensitive tasks like banking is not recommended, as it contains known vulnerabilities.

Website Errors: You may encounter "Your connection is not private" or certificate errors on modern websites because the browser's built-in security certificates are outdated.

Upgrade Options: If your hardware allows, upgrading to macOS 10.13 (High Sierra) would let you run Firefox 115 ESR, which is significantly newer and more secure. How to update outdated browser on OS X Yosemite

It looks like you’re trying to find a Firefox download for Mac OS X 10.10.5 (Yosemite).

However, the latest versions of Firefox no longer support OS X 10.10.5. Mozilla ended support for 10.10, 10.11, and 10.12 after Firefox 78 (ESR) and Firefox 79+.

Here’s what you can do:

  1. Use Firefox Extended Support Release (ESR) 78 – this is the last version compatible with 10.10.5.

  2. Or download from Mozilla’s official “Firefox for older Macs” page:

  3. Note: Using Firefox 78 ESR means no new features, and security updates ended in 2021. For better security, consider updating macOS (if your Mac supports it) or switching to a lightweight browser like Pale Moon or Arctic Fox (community-maintained for older macOS).

If you meant macOS 10.15 (Catalina) instead of 10.10.5, let me know and I’ll give you the latest compatible Firefox link.

Firefox Download for Mac 10105: A Step-by-Step Guide

Are you looking to download and install Firefox on your Mac? Look no further! In this post, we'll walk you through the process of downloading and installing Firefox on your Mac, as well as provide some additional information about the browser.

Why Choose Firefox?

Firefox is a popular web browser that offers a range of benefits, including:

  • Speed: Firefox is known for its fast browsing speeds and responsive performance.
  • Security: Firefox has a strong focus on security, with features like tracking protection and regular updates to keep you safe online.
  • Customization: Firefox offers a range of customization options, including themes, extensions, and user interface tweaks.
  • Cross-platform compatibility: Firefox is available on multiple platforms, including Mac, Windows, and Linux.

Downloading and Installing Firefox on Mac

To download and install Firefox on your Mac, follow these steps:

  1. Go to the Firefox website: Open a web browser (such as Safari or another browser of your choice) and navigate to the Firefox website at www.mozilla.org.
  2. Click on the "Download Now" button: In the top right corner of the page, you'll see a button that says "Download Now". Click on this button to begin the download process.
  3. Select the correct version: Make sure you're selecting the correct version of Firefox for your Mac (e.g. macOS 10.12 or later).
  4. Wait for the download to complete: The download process should begin automatically. Depending on your internet connection, this may take a few seconds or a few minutes.
  5. Open the downloaded file: Once the download is complete, open the downloaded file (which should be named "Firefox.dmg").
  6. Drag and drop Firefox into your Applications folder: In the Firefox installer window, drag and drop the Firefox icon into your Applications folder.
  7. Eject the disk image: Once the installation is complete, eject the disk image by clicking on the eject icon in the Finder sidebar.
  8. Launch Firefox: You can now launch Firefox by finding it in your Applications folder and double-clicking on it.

Updating Firefox on Mac

To ensure you have the latest version of Firefox, follow these steps:

  1. Open Firefox: Launch Firefox on your Mac.
  2. Click on the Firefox menu: In the top left corner of the screen, click on the Firefox menu.
  3. Select "About Firefox": From the dropdown menu, select "About Firefox".
  4. Check for updates: In the About Firefox window, click on the "Update Firefox" button to check for any available updates.
  5. Install updates: If an update is available, follow the prompts to install it.

Firefox Version 10105: What's New?

Firefox version 10105 is a relatively minor update that includes some bug fixes and performance improvements. Some of the key changes include:

  • Improved performance: Firefox 10105 includes some performance tweaks that should make browsing faster and more responsive.
  • Bug fixes: This update includes fixes for several bugs and issues that were present in previous versions of Firefox.

Conclusion

Downloading and installing Firefox on your Mac is a straightforward process that can be completed in just a few minutes. With its focus on speed, security, and customization, Firefox is a great choice for Mac users looking for an alternative to Safari or other browsers. If you're looking for a reliable and feature-rich browser, Firefox is definitely worth checking out!

For macOS 10.10.5 (Yosemite), the final compatible version of Firefox is Firefox 78.15.0esr. Because modern versions of Firefox require macOS 10.15 or later, you must manually download this specific "Extended Support Release" (ESR) version from Mozilla’s archives. Guide to Downloading Firefox for Mac 10.10.5

Download the Correct Version:Access the official Mozilla archive to download the compatible installer directly: Download Firefox 78.15.0esr (English US).

If you need a different language, navigate the Mozilla FTP directory to find your specific locale folder. Installation Steps:

Locate the downloaded .dmg file in your Downloads folder and double-click it.

A window will appear; drag the Firefox icon into your Applications folder.

Open Firefox from your Applications folder. You may see a security warning since it is an older version; click Open to proceed.

Disable Automatic Updates:To prevent Firefox from trying to update to an incompatible version, you should immediately disable automatic updates:

Click the Firefox menu (three horizontal lines) and select Settings.

In the General panel, scroll to the Firefox Updates section.

Select Check for updates but let you choose to install them and uncheck Use a background service to install updates. Important Considerations

Security Risks: Firefox 78 ESR stopped receiving security updates in October 2021. Using it for sensitive activities like online banking is not recommended as it lacks modern protection against newer threats.

Website Compatibility: Some modern websites may not load correctly or may display formatting issues because this version of Firefox does not support the latest web standards.

Better Alternatives: If your hardware supports it, consider upgrading your OS to macOS 10.11 (El Capitan) or 10.13 (High Sierra) to use slightly newer (though still aging) browsers like Firefox 115 ESR.

How to Download Firefox for Mac OS X 10.10.5 (Yosemite) If you’re still using a classic Mac running OS X 10.10.5 Yosemite

, you may have noticed that many modern browsers no longer support your operating system. However, you can still get a functional and relatively secure version of Firefox to keep your machine surfing the web. The Last Compatible Version: Firefox 78 ESR

For users on Mac OS X 10.10.5, the most up-to-date official version available is Firefox 78 Extended Support Release (ESR)

. This was the final major release to support Yosemite before Mozilla moved its minimum requirements to macOS 10.12 Sierra and later. Firefox 78.15.0esr

This version is no longer receiving security updates as of October 2021. Why use it?

It is generally more compatible with modern websites than the outdated version of Safari that comes with Yosemite. Step-by-Step: How to Download and Install Since the main Firefox Download Page

will automatically try to give you the newest version (which won't open on 10.10.5), you need to follow these steps: Locate the Correct Installer : You can find older versions on the Mozilla CDN server or through reputable archives like Download the DMG : Save the Firefox 78.15.0esr.dmg file to your Downloads folder. : Open the DMG file and drag the Firefox icon into your Applications folder

: Open your Applications folder and double-click Firefox. If you see a warning about an app "downloaded from the internet," click Important Tips for Legacy Users Security Risks

: Because Firefox 78 ESR has not had security patches in years, avoid using it for sensitive tasks like online banking. Website Issues : If a site looks "broken," it might be due to Enhanced Tracking Protection . Click the shield icon

in the address bar to try disabling it for that specific site. Upgrade Options : If your hardware allows it, consider upgrading your OS to 10.11 El Capitan 10.13 High Sierra . High Sierra supports Firefox 115 ESR

, which remained supported with security updates much longer.

For macOS 10.10.5 (Yosemite), the final supported version of Firefox is Firefox 78 ESR. You can still find this legacy installer through official Mozilla Support channels or verified archives like Macintosh Repository. The Ghost in the Machine: A Yosemite Elegy

There is a particular kind of stubbornness required to maintain a Mac running OS X 10.10.5 Yosemite. In the fast-paced timeline of Silicon Valley, a decade-old operating system is effectively a fossil. Yet, for those of us still clutching our 2012 MacBooks, Yosemite isn't just software; it's a preserved ecosystem, a digital time capsule of flat icons and translucent sidebars that marked the transition into Apple's modern aesthetic.

The challenge of living in this past is the narrowing window to the present: the web browser. As security protocols evolve, the modern web slowly "blinds" older machines. This is where Firefox 78 ESR (Extended Support Release) enters the story as a loyal companion. It was the final version to keep the lights on for Yosemite before the support bridge was officially dismantled in October 2021.

Downloading Firefox 78 for an aging Mac is an act of digital preservation. It allows an old friend to continue "buying cat food and banking," as one archivist poignantly put it. It is the difference between a functional tool and a beautiful aluminum brick. We keep these machines not because we can't afford the new, but because the old still works, its keys worn smooth by years of shared history. In a world of planned obsolescence, choosing to find that one compatible installer is a small, quiet rebellion—a way of saying that even in the digital age, some things are worth keeping around.

It is important to note that Firefox no longer supports macOS 10.10.5. The current version of Firefox requires macOS 10.15 (Catalina) or newer.

However, you can still install a working version of Firefox on your Mac, but you must install an older version (Firefox 78.15.0 ESR).

Problem: Profile from newer Firefox won’t load

Solution: Firefox 78 ESR cannot read profiles from Firefox 90+. Create a fresh profile:
/Applications/Firefox.app/Contents/MacOS/firefox-bin -P

1. Understanding “Firefox Download for Mac 10105 upd” – What Does It Mean?

Before downloading, let’s break down the keyword:

  • Mac 10105 → Mac running OS X version 10.10.5 (build 14F27 or similar). This is Yosemite’s final point release.
  • Upd → “Update” – You want the newest Firefox version that still works on 10.10.5, not an ancient original release.

Critical fact: Mainstream Firefox (Versions 78+) dropped support for OS X 10.10 and 10.11 in mid-2021. The last compatible series is Firefox 78 ESR (Extended Support Release). However, a later ESR – Firefox 91 ESR – initially required macOS 10.12+. But community reports indicate Firefox 78.15.0esr is the final official build for 10.10.5.

If you try to install a newer Firefox (version 100+), the installer will fail with an error: “You cannot use this version of Firefox with this version of macOS.”

Thus, firefox download for mac 10105 upd effectively means: Get the latest Firefox 78.x ESR update.

9. Frequently Asked Questions

Q: Can I get Firefox 91 ESR on 10.10.5?
A: No, it requires macOS 10.12+. No reliable upd exists.

Q: Is there a “firefox download for mac 10105 upd” that is 115 ESR?
A: Absolutely not. Firefox 115 ESR requires macOS 10.15+.

Q: How can I tell my exact macOS version?
A: Apple menu → About This Mac. Look for “Version 10.10.5”.

Q: What if my download fails?
A: Use curl in Terminal:
curl -O https://archive.mozilla.org/pub/firefox/releases/78.15.0esr/mac/en-US/Firefox%2078.15.0esr.dmg

Q: Will my bookmarks sync?
A: Yes – Firefox Sync works on 78 ESR (sign in with a Mozilla account).

Step 1: Uninstall any broken or partial Firefox versions

Before installing the legacy version, open your Applications folder. If you see a greyed-out Firefox icon with a "no entry" sign, drag it to Trash. Also empty your Trash to avoid permission conflicts.

7. Security Warning for Legacy Macs

Running Firefox 78.15 in 2026 means no new security patches for Firefox-specific vulnerabilities (CVEs after Nov 2021 are unpatched). However:

  • macOS 10.10.5 itself has unpatched kernel exploits – use common sense: avoid untrusted sites, use uBlock Origin, disable JavaScript on unknown sites.
  • For banking or sensitive work, consider upgrading your Mac (or using a lightweight Linux distro like Linux Mint Xfce on the same hardware).

Firefox download for mac 10105 upd gives you the best available browser, but not a perfect shield.