Internally, TenFourFox FPR1 is versioned as 45.10.0 to maintain add-on compatibility (but read on for an important caveat), and all FPRs will be based on our fork of Firefox ESR 45, though the About box and the user agent show the current parity release level. This release primarily concentrated on performance and I liberally
Also new in FPR1 is official support for Brotli, a more efficient compression mechanism than the gzip and DEFLATE methods we currently support. Mozilla disabled this in 45 due to bugs; I secretly backported the version from ESR52 with the bugs fixed and made the (small number of) necessary changes to the browser for 45.9, which this version now enables by default. It only operates over HTTPS and on those sites that support it, but this number is expected to grow as Chrome, Firefox, Microsoft Edge and Opera all accept it.
I've also been backporting relevant security patches from 52ESR to 45ESR, and our tree is now able to accept updated TLS root certificates, pinned certificates and HSTS data from 52ESR more or less directly. Eventually I still plan to update to the NSS library in 52ESR so that we can get additional cipher and encryption support, but this suffices for now. Please note that, as
threatened promised, all SHA-1-only certificates are now untrusted. Most of the ESR security patches to date have been applied to the version you will be trying out except for a couple of very large changesets that need a bit more evaluation. We will be at full security parity for all known issues by the date of release.
Speaking of release date, FPR1 will be a bit delayed as I will be taking a brief vacation and I won't be at my G5 for a little while. Mozilla's release schedule has 54/52.2 coming out on June 13, which won't give me enough time to complete my work and do internal testing (hey, I'm entitled to some time off), so my current plan is to release FPR1 on or before June 27 and then catch up for FPR2 with the release of 55/52.3 on August 8. It is possible that I may delay future FPR releases until a couple days after the main ESR is released for testing and backporting reasons, but let's see how close I can adhere to the schedule still.
For builders, now that our Github is off and running, there's no need to continue distributing changesets; future releases at SourceForge will have just a placeholder instead of a zip file for source. Instead, please kindly refer to the updated build instructions.
Oh, one more thing: it looks like someone is working on an Intel version of TenFourFox again (compatible with at least 10.6 and possibly even 10.5). I won't say whom because it may be some time before anything is available, and as I've always said, this is not a release I can personally maintain even though I am happy to support and advise someone willing to, but their early work looks promising and they appear to have sufficient expertise to make it happen. Once their changes make it back into the TenFourFox github we can consider it "officially a thing." Meanwhile, although the development is occurring more or less in the open and you can probably find it without much effort, please don't pester me or them about it since it hasn't gotten off the ground yet.
Post observations in the comments and feel free to star or watch the Github repo for updates.