Version 128 can translate text selections and hyperlinked text to other languages from the context menu."

It also has a simpler and more unified dialogue for clearing user data. In addition to streamlining data categories, the new dialogue provides insights into the site data size corresponding to the selected time range.

On macOS, microphone capture through getUserMedia will now use system-provided voice processing when applicable, improving audio quality."

The most important feature of version 128 is that it is the newest ESR (Extended Support Release), which is the browser of choice for many Linux distributions (including Debian), which is important for the Linux community.

Many downstream projects (like Thunderbird or KAiOS) use Firefox ESR as their base, so whatever is included in version 128 will determine their capabilities for the next year.

Many ISVs (software makers), both big and small, test and certify their software only against the ESR version of Firefox. For users of such software, the new ESR is essential.

Many companies and individuals value the stability of the UI/Workflow over new features, so ESR is important to them.

When an OS is discontinued, Mozilla lets the ESR be the last browser on the platform, extending the support window beyond what companies like Alphabet, Apple, or Microsoft offer. So, for people on older OSs, ESR is important.