It works well, but unsurprisingly, they screwed up privacy once again by sending data to some company ( https://www.adjust.com ) in the background: http://www.theregister.co.uk/2016/11/17/mozilla_launches_pri... Doesn't seem to be possible to turn it off (the instructions at https://support.mozilla.org/en-US/kb/send-anonymous-usage-da... : do not work, there is no such settings menu for "Klar by Firefox"?). Perhaps I…
> For a new install, the application sends an anonymous "attribution" request to the adjust servers. This request describes how the application was downloaded, for example, whether it was downloaded directly via the App Store or through a marketing campaign link. The data includes an advertising ID, IP address, timestamp, country, language/locale, operating system and app version.
> Firefox for iOS, Firefox Focus, Firefox Klar and Android will also occasionally send anonymous summaries about how often the application has been used. These summaries only include information regarding whether the app has been in active use recently and when.
> Additionally, Firefox Focus and Firefox Klar will also report what features of the application are being used. It will send an anonymous report containing the specific filters being selected and count how many times the search, browse and erase button is pressed.
(also from https://support.mozilla.org/en-US/kb/send-anonymous-usage-da...)
Per the instructions at the bottom: "If you are in the browser you may have to hit the Erase button first" - did you do this when looking for the settings?