Selenium IDE works with all Firefox versions, but 47.0.1 & above is recommended to use as they have better stability. Remember that Selenium IDE is no longer compatible with Firefox 55 and above.
You can download selenium IDE using the following steps:
- Launch the Firefox and navigate to https://addons.mozilla.org/en-US/firefox/addon/selenium-ide/. Then click on Add to Firefox
- Wait until the download is done, then click "Install"
- Wait until the installation is completed. In the pop-up window, click "Restart Now"
After Firefox has restarted, launch Selenium IDE using either by pressing Ctrl+Alt+S or by clicking on the Firefox menu button> Developer>Selenium IDE
Selenium IDE should launch.