Published: May 2026
Reading Time: 6 minutes
If you’ve searched for “firefox download for mac 10105 upd” , you are likely running an older Mac – specifically one capped at macOS 10.10.5 (Yosemite) or a similar legacy build (e.g., 10.11, 10.12). The “upd” in your query suggests you need the latest possible update for that environment.
Apple no longer supports OS X Yosemite, but Mozilla has historically provided extended support releases (ESR) for older Macs. This article will walk you through exactly how to find, download, install, and troubleshoot Firefox for Mac OS X 10.10.5, ensuring you get the final secure update available.
Mozilla regularly updates Firefox to include new web standards, security protocols, and performance optimizations. However, modern software requires modern operating system foundations.
If you attempt to install a newer Firefox (version 80 or above) on 10.10.5, the installer will fail. You need the legacy build.
If you are still running OS X Yosemite (10.10.5) and trying to get the latest version of Firefox, you have likely hit a wall. Modern software moves fast, and support for older operating systems eventually falls by the wayside.
Here is the breakdown of what version you can run, why you can’t update further, and how to stay safe.
.dmg file.Applications folder.Applications folder and launch Firefox.Summary
Important note
Download & install steps
Security and compatibility tips
If you want, I can draft a short webpage blurb, email, or step-by-step checklist tailored for end users or IT staff.
For users running macOS 10.10.5 (Yosemite), the latest and final compatible version of Firefox is Firefox 78.15.0esr. Summary of Support
Modern versions of Firefox no longer support macOS 10.10. Support for this operating system officially ended on October 5, 2021.
Final Version: Firefox 78.15.0esr (Extended Support Release).
Current Status: This version no longer receives security updates from Mozilla. How to Download
Since the standard Firefox Download Page will typically offer the newest version (which requires macOS 10.15 or later), you must manually download the legacy installer.
Official Mozilla Archive: You can find older versions via the Mozilla Support Forum or directly from the Mozilla FTP Archive.
Third-Party Repositories: Sites like Uptodown and MacUpdate maintain archives of older .dmg files if the official archive is difficult to navigate. Recommendations for Older Macs firefox download for mac 10105 upd
Running an outdated browser on an unsupported OS poses security risks. To use the latest version of Firefox:
Check for OS Updates: See if your Mac can be updated to at least macOS 10.15 (Catalina) or higher.
Use Safari for Downloads: If your current browser is struggling to load modern HTTPS websites, use the native Apple Safari to download the Firefox installer.
Alternative Browsers: If Firefox 78 does not meet your needs, some users on legacy macOS versions look toward community-maintained browsers like Pale Moon or SeaMonkey, though compatibility varies.
If you are looking to update Firefox on Mac OS X 10.10.5 (Yosemite), it is important to note that Mozilla has officially ended support for this operating system.
Here is the information you need regarding the final compatible version and how to download it: The Final Compatible Version
The last version of Firefox that supports Mac OS X 10.10 is Firefox 78.15.0esr (Extended Support Release).
No New Updates: Version 78.15.0esr was the final "end of life" update for Yosemite users. You will not receive new features or security patches beyond this version.
Official Download: You can download this specific legacy version directly from the Mozilla FTP Archive. How to Install
Download the DMG: Click the link above and select the .dmg file. Open the Installer: Double-click the downloaded file.
Drag to Applications: Drag the Firefox icon into your Applications folder.
Confirm Open: Because it is an older version, macOS may ask for confirmation before opening the app for the first time. Security Warning
Using an outdated browser on an unsupported operating system poses security risks. Because Firefox 78.15.0esr no longer receives security updates, your data may be more vulnerable to modern web threats.
If your hardware allows, it is highly recommended to update your macOS to a newer version (10.15 or later) to use the latest, most secure version of Firefox.
For users on Mac OS X 10.10.5 (Yosemite) , the journey to a modern browsing experience has a specific finish line. Since 2021, Mozilla has officially ended support for this operating system version, but there is still a way to get a compatible version running. Apple Support Community The Recommended Version: Firefox 78 ESR
The latest and final version of Firefox that works on Mac OS X 10.10.5 is Firefox 78 Extended Support Release (ESR) Mozilla Support Current Status
: This version is no longer receiving security updates as of October 2021. Functionality
: While it can still browse many websites, some modern features or highly secure sites may encounter compatibility issues. Apple Support Community How to Download and Install The Ultimate Guide: Firefox Download for Mac 10105
Since the main Firefox download page will typically offer the newest version (which requires macOS 10.15 or later), you must use the official archive for the older version. Mozilla Support Download the Installer : Access the Official Mozilla Archive for 78.15.0esr to download the Open the DMG
: Double-click the downloaded file to open the installer window. : Drag the Firefox icon Applications folder
: Open Firefox from your Applications folder. You may need to click "Open" on a security prompt since it is an older software package. Mozilla Support Why You Can't Get Newer Updates
Mozilla moved users on OS X 10.9, 10.10, and 10.11 to the Extended Support Release (ESR) channel to provide a few extra years of security. However, maintaining support for decade-old operating systems became unsustainable as web technologies evolved. Mozilla Support Better Alternatives for Your Mac
If your hardware allows it, experts recommend upgrading your macOS to at least 10.15 Catalina
or higher to use the latest, most secure version of Firefox.
For users still running macOS 10.10.5 (Yosemite), the final supported version of Firefox is Firefox 78.15.0 ESR (Extended Support Release).
Because modern versions of Firefox (version 79 and later) require macOS 10.12 or newer, you must manually download the legacy installer to maintain functionality on Yosemite. Download and Installation Guide Locate the Legacy Installer:
Navigate to the official Mozilla FTP archive or the Mozilla Support page for legacy systems . Download the file named Firefox 78.15.0esr.dmg. Install the Application: Open the downloaded .dmg file from your Downloads folder. Drag the Firefox icon into your Applications folder.
If prompted to replace an existing version, select "Replace" to ensure the older, compatible version is installed. Bypassing Security Warnings:
Upon first launch, you may see a warning that the app was downloaded from the internet. Click Open.
If macOS prevents the app from opening, go to System Preferences > Security & Privacy > General and click Open Anyway. Critical Support Information How to update outdated browser on OS X Yosemite
Report: Firefox Support for macOS 10.10.5 (Yosemite) Executive Summary
Mozilla Firefox no longer officially supports macOS 10.10.5 (Yosemite) with its current releases. The final official version compatible with this operating system is Firefox 78.15.0esr (Extended Support Release)
. Users remaining on this legacy OS face significant security risks as this version ceased receiving critical security updates in October 2021. Technical Findings Last Compatible Version
: Firefox 78.15.0esr is the terminal build for macOS versions 10.9 through 10.11. Security Status
: End-of-life. No further security patches or feature updates are provided, leaving the browser vulnerable to modern exploits. Modern Compatibility
: Current mainstream versions of Firefox (e.g., Firefox 130.0+) require macOS 10.15 (Catalina) or later. Download Resources Why Standard Firefox No Longer Works on 10
For users who must maintain a legacy Yosemite environment, installers can still be sourced from historical archives: How to update outdated browser on OS X Yosemite
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.
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).
Mozilla no longer links old versions directly. Use the official archive:
🔗 Mozilla FTP directory (safe, official):
https://ftp.mozilla.org/pub/firefox/releases/78.15.0esr/mac/
Steps:
en-US (or your locale folder).Firefox%2078.15.0esr.dmg (or similar .dmg file)..dmg → drag Firefox to Applications.✅ Checksum verification (optional but recommended):
SHA256SUMS.