I believe you'll have to redownload the stable version of Firefox (I don't think it's possible to switch directly from ESR to stable).

However, you shouldn't see much of a performance difference between the two versions (the main difference is that ESR is updated with new features less often). I would take a look at Quick fixes if your Firefox slows down for some basic troubleshooting steps you can take for performance issues.

Support for Windows 7, 8, 1.8 and macOS 10.12, 10.13, 10.14 OS have been dropped as of Firefox 116 and later as to why you were served the Firefox 115.1.0 ESR.

Since you have Windows 10 yo can install the 116.0 Release from https://www.mozilla.org/firefox/all/#product-desktop-release as this will give you the full offline setup and not the small online stub installer.

However, you shouldn't see much of a performance difference between the two versions (the main difference is that ESR is updated with new features less often).

To be more accurate, the ESR channel does not see any new features until the next major version based on a Firefox Release. The Fx 115 ESR is based on the Fx 115 Release and ESR only gets security and stability updates.

If you are on Windows 10 then you can uninstall the Firefox 115 ESR and download and install the current release.

You can find the full installer of the current Firefox release (116.0) in all languages and all operating systems here:

• https://www.mozilla.org/en-US/firefox/all/#product-desktop-release
• https://www.mozilla.org/en-US/firefox/116.0/releasenotes/

It might be a good idea to create a new profile to ensure no remnants of using Windows 7 are left.

See "Creating a profile":

• https://support.mozilla.org/en-US/kb/profile-manager-create-remove-switch-firefox-profiles

If the new profile works, you can transfer files from a previously used profile to the new profile, but be cautious not to copy corrupted files to avoid carrying over problems.

• https://support.mozilla.org/en-US/kb/recovering-important-data-from-an-old-profile
• https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data

• bookmarks and history: places.sqlite
• favicons: favicons.sqlite
• bookmark backups: compressed .jsonlz4 JSON backups in the bookmarkbackups folder
• cookies.sqlite for the Cookies
• formhistory.sqlite for saved autocomplete Form Data
• logins.json (encrypted logins) and key4.db (encryption key and primary password) for logins saved in the Password Manager
• cert9.db for certificates stored in the Certificate Manager
• persdict.dat for words added to the spell checker dictionary
• permissions.sqlite for Permissions and possibly content-prefs.sqlite for other website specific data (Site Preferences)
• sessionstore.jsonlz4 for open tabs and pinned tabs (see also the sessionstore-backups folder)