How to Install an Older Version of Firefox on Ubuntu

Installing an older version of Firefox on Ubuntu primarily involves manually downloading the desired version's binary, installing necessary dependencies, and configuring it to run on your system. This method bypasses the default package management system, providing direct control over the Firefox version you use.

Why Install an Older Version of Firefox?

There are several reasons why a user might need to install an older version of Firefox:

Compatibility: Some legacy web applications or specific websites might only function correctly with an older browser engine.
Add-on Support: Certain essential add-ons or extensions might not be compatible with newer Firefox releases or might have been discontinued.
Testing: Developers often need older browser versions for testing web applications across different environments.
Performance: In rare cases, an older version might perform better on very old or resource-constrained hardware for specific tasks.

Prerequisites

Before you begin, ensure you have:

Administrator Privileges: You'll need sudo access to install dependencies and move files to system directories.
Desired Firefox Version: You must download the .tar.bz2 archive for the specific older Firefox version you want. You can typically find these on the official Mozilla FTP archives, such as ftp.mozilla.org/pub/firefox/releases/.
Internet Connection: To download the Firefox archive and any required dependencies.

Step-by-Step Installation Guide

Follow these steps carefully to install an older version of Firefox on your Ubuntu system.

Step 1: Download the Older Firefox Version

Navigate to the Mozilla FTP archive and download the specific version you need. For example, to download Firefox 45.0.2 for Linux 64-bit, you might navigate to ftp.mozilla.org/pub/firefox/releases/45.0.2/linux-x86_64/en-US/.

# Example: Download Firefox 45.0.2 (replace with your desired version and architecture)
wget -O ~/Downloads/firefox-45.0.2.tar.bz2 "https://ftp.mozilla.org/pub/firefox/releases/45.0.2/linux-x86_64/en-US/firefox-45.0.2.tar.bz2"

Step 2: Backup or Remove Existing Firefox (Optional but Recommended)

It's crucial to manage your existing Firefox installation to prevent conflicts.

Check for Existing Installation: Determine if a Firefox installation already exists, particularly in the /usr/lib/firefox directory.
```
ls -l /usr/lib/firefox
```
Backup the Existing Installation: If Firefox is present in /usr/lib/firefox, move it to a backup location. This is especially important if you installed Firefox manually before.
```
sudo mv /usr/lib/firefox /usr/lib/firefox_backup
```
Alternatively, if Firefox was installed via apt, you might consider uninstalling it first:
```
sudo apt remove firefox
```

Step 3: Install Essential Dependencies

Older versions of Firefox may rely on specific libraries that are not always present or are different in newer Ubuntu versions. One common dependency is libgtk2.0-0.

sudo apt-get install libgtk2.0-0

Depending on the specific older version and your Ubuntu release, other dependencies might be required. If Firefox fails to launch later, check the terminal for error messages indicating missing libraries.

Step 4: Extract the Downloaded Archive

Navigate to your Downloads directory (or wherever you saved the .tar.bz2 file) and extract the archive.

cd ~/Downloads
tar xvf firefox-45.0.2.tar.bz2 # Replace 45.0.2 with your downloaded version

This command will create a new directory named firefox (or similar) containing the extracted browser files.

Step 5: Move Firefox to the System Directory

For system-wide access and easier management, move the extracted Firefox directory to /usr/lib/.

sudo mv firefox/ /usr/lib/firefox

This command moves the firefox directory from your Downloads folder to /usr/lib/. The new Firefox binary will now be accessible at /usr/lib/firefox/firefox.

Step 6: Create a Symbolic Link and Desktop Launcher (Recommended)

To make launching easier and ensure the system recognizes your new installation, create a symbolic link and a desktop launcher.

Create a Symbolic Link: This allows you to run Firefox by simply typing firefox in the terminal.
```
sudo ln -sf /usr/lib/firefox/firefox /usr/bin/firefox
```

Create a Desktop Launcher: This provides an icon for easy access from your application menu.

Create a file named ~/.local/share/applications/firefox-old.desktop (or /usr/share/applications/firefox-old.desktop for system-wide access) with the following content:

[Desktop Entry]
Name=Firefox (Old Version)
Comment=Web Browser (Older Version)
Exec=/usr/lib/firefox/firefox %u
Terminal=false
Type=Application
Icon=/usr/lib/firefox/browser/chrome/icons/default/default128.png # Path to Firefox icon
Categories=Network;WebBrowser;
MimeType=text/html;text/xml;application/xhtml+xml;application/xml;application/vnd.mozilla.xul+xml;application/rss+xml;application/rdf+xml;image/gif;image/jpeg;image/png;
StartupWMClass=firefox-old

You might need to adjust the Icon path depending on the Firefox version. Find a suitable icon within the /usr/lib/firefox directory structure.

Important Considerations

Security Risks: Running older versions of Firefox can expose you to known security vulnerabilities that have been patched in newer releases. Use older versions only when absolutely necessary and ideally in isolated environments.
Manual Updates: Older Firefox installations using this method will not receive automatic updates. You will need to manually download and replace the files if you wish to update to a newer (but still older than the latest) version.
Profile Management: Firefox profiles store your bookmarks, history, and settings. Newer Firefox versions might not be compatible with profiles created by very old versions, and vice-versa. Consider using a separate profile for your older Firefox installation by launching it with firefox -P.
System Integration: Some system features or extensions expecting the default Firefox installation might not work seamlessly with a manually installed older version.

Summary of Key Commands

The following table summarizes the primary commands used in this process:

Command	Description
`wget -O ~/Downloads/firefox-XX.Y.Z.tar.bz2 URL`	Downloads the specified Firefox archive.
`sudo mv /usr/lib/firefox /usr/lib/firefox_backup`	Backs up an existing Firefox installation.
`sudo apt-get install libgtk2.0-0`	Installs a common dependency for older Firefox versions.
`tar xvf firefox-XX.Y.Z.tar.bz2`	Extracts the downloaded Firefox archive.
`sudo mv firefox/ /usr/lib/firefox`	Moves the extracted Firefox to the system's library directory.
`sudo ln -sf /usr/lib/firefox/firefox /usr/bin/firefox`	Creates a symbolic link for easy execution.

By following these steps, you can successfully install and run an older version of Firefox on your Ubuntu system, enabling compatibility with specific requirements.