Our currentDepending on user-agent string does not include the word "Firefox"., This can result insome web browsing failures on websites that persist in using to load due to use of UA sniffing (rather than, say, feature detection or defensive programming). Shall we:
1. Keep defacto policy. Drop "Firefox", add "PureBrowser".User-agent is a string of this form: `Mozilla/[version] ([system and browser information]) [platform] ([platform details]) [extensions]`
2. Use IceWeasel-style policy. Keep "Firefox"Options:
* Plain: Include `PureBrowser` in extensions
* Compatibility mode: Include `Firefox` and `PureBrowser` in extensions
* Impersonation: Include `Firefox` in extensions
* Subtle: Include `PureBrowser in browser information, add "PureBrowser".and `Firefox` in extensions
3. Use IceCat- and Tor-style policy. Keep "Firefox", do not addPlain is the default when Firefox is built with "Brand" changed to "PureBrowser".
4. Something else / additional details?Compatibility mode is the style when a rebranded Firefox is runtime-configured with `general.useragent.compatMode.firefox` enabled.
This has been applied to PureBrowser since 52.9.0esr-1pureos2.
Other considerations:Impersonation is practiced e.g. by GNU IceCat fork of Firefox (see https://tracker.pureos.net/w/troubleshooting/firefox_compat_mode/).
* Examples of failures include:
* AMO, wide reach, impacts access to arbitrary add-ons. Even IceCat supports AMO access (they just don't promote it). https://tracker.pureos.net/T202
* Jitsi Meet, lower reach, impacts access but they are willing to accept a patch. https://tracker.pureos.net/T201Subtle is suggested by Mozilla as acceptable for AMO (see T595#11999).
Examples of failures include AMO (see T202) and Jitsi Meet (see T201).
* An idiosyncratic UA string has privacy implications (see https://panopticlick.eff.org -- there are many other tracking signals, but any idiosyncrasy has an impact)
* This would suggest opimpersonation 3mode is preferable.
* We don't want to commit to "keep Panopticlick score as low as possible", Tor is better suited to that use case. This change should not be read as implying that.
* What are the benefits of an idiosyncratic UA? Measuring browser reach globally. Measuring browser reach on our own sites. What value does this have? Any other benefits? If there is value here, we could take the IceWeasel approach.
* Global scale trackers may count us as Firefox if we include "Firefox" in the UA string. Is this good or bad?