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How to downgrade a Firefox install on old iMac (late 2009) when I can't open browser?

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  • Last reply by cor-el

Ashley KD
Ashley KD
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Hi, the turbotax website forced me to update Firefox and since I did, I am no longer able to open the browser at all. The error message reads, "You can't use this version of the application "Firefox" with this version of OS X. You have OS X 10.11.6. The application requires OS X 10.12 or later." Unfortunately, from what I have read, I can't get that update that on my iMac (21.5inch, late 2009) OS X El Capitan Version 10.11.6. Is there any way to downgrade the Firefox install? I can't even see what previous version of Firefox I had before because I can't open the browser anymore. If anyone can help I would be super grateful. Thanks in advance!

Hi, the turbotax website forced me to update Firefox and since I did, I am no longer able to open the browser at all. The error message reads, "You can't use this version of the application "Firefox" with this version of OS X. You have OS X 10.11.6. The application requires OS X 10.12 or later." Unfortunately, from what I have read, I can't get that update that on my iMac (21.5inch, late 2009) OS X El Capitan Version 10.11.6. Is there any way to downgrade the Firefox install? I can't even see what previous version of Firefox I had before because I can't open the browser anymore. If anyone can help I would be super grateful. Thanks in advance!

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cor-el
cor-el
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Firefox 78.15.0 ESR is the last version for Mac OS X 10.9/10.10/10.11 (distributionID: mozilla-mac-eol-esr1) and you will no longer receive updates.

Firefox 78.15.0 on the Mozilla CDN server:

Mac OS users on OS X 10.12/10.13/10.14 have been moved to the 115 ESR update channel since this platform no longer is supported, current releases require macOS 10.15 as a minimum.