When connecting to a remote server, Firefox uses TLS (transport layer security) protocol to encrypt the data transfer. There are many versions of TLS in use but the older versions are now considered weak and are being gradually abandoned both by the web browsers and the web hosting providers.
With the release of version 74.0 of Firefox web browser, Mozilla has decided to disable older deprecated versions of the TLS protocol namely TLS 1.0 and TLS 1.1. From now on you will be able to access only the websites that have support for TLS 1.2 and TLS 1.3. But if you want to access some website that has not been upgraded to a later version of TLS, you can still enable the older versions of TLS in Firefox.
Here is how you can enable TLS 1.0 and TLS 1.1 in Firefox browser once again:
- Type about:config in the Firefox address bar and press Enter.
- Type tls.version in the search box to find the settings we want to change.
- Double-click on a setting named security.tls.version.enable-deprecated to change its value to true.
- All done. Now Firefox once again supports older TLS versions.
In order to check which versions of TLS your web browser supports, you can visit https://browserleaks.com/ssl and it will automatically examine your browser before displaying the results. Before making the above changes, it will display that TLS 1.0 and TLS 1.1 are disabled. After the changes, it will display that these older versions of TLS are enabled but with a warning that these versions of TLS are weak. This is the main reason why Mozilla has decided to disable them by default.
You should enable TLS 1.0 and TLS 1.1 only and only in emergency situations when you want to access a known safe website that does not support TLS 1.2 or later versions. This should not be made a permanent change as it will weaken the security of your Firefox web browser. Website owners should also switch to the web servers that support TLS 1.2 and TLS 1.3 as soon as possible.