Compatibility/Telemetry

Measuring web compatibility

This page tracks the telemetry measurements that the Web Compat team is tracking. See Telemetry for more information.

Bug 1109958 will serve as the meta tracking bug for all telemetry probes.

Q1 probe goals

These are the probes we want to try to land in Q1. Please only add to this list if you're willing to take on the required work.

• WAP (WML or XHTMLMP) content type

We not infrequently receive bugs in Bugzilla about WAP content being sent to Fennec and Firefox OS users (see bug 941241, bug 997668, with dependencies, among others.). We intend to gather telemetry data to understand how common this is for Firefox mobile users. Once we understand the frequency and severity of the problem (measured as WAP vs non-WAP content type responses) we can decide how to proceed. Possible decisions include: support re-parsing of WAP content as HTML, showing an error message in the developer console, WONTFIXing related bugs and continuing to do Tech Evangelism as issues arise.

A telemetry probe (HTTP_WAP_CONTENT_TYPE_RECEIVED histogram) was landed in bug 1121559 on January 21, 2015.

• Media formats (ogg, mp4, h264, m3u8/HLS)
• Media MIME types
  • HTMLMediaElement.canPlayType()
  • MediaSource.isTypeSupported()
  • MediaSource.addSourceBuffer(DOMString type)
• H264
  • H.264 AVC profile info (profile/flags/level)
  • FRext in SPS
  • SPS.max_num_ref_frames (see https://bugzilla.mozilla.org/show_bug.cgi?id=1125340#c19

Idea bucket (sanity not guaranteed)

CSS

• `display: table` with `max-width: 100%` on children (see 434230 and 975632 )

HTTP

• `Server:` name
• Redirection sequences
• Wrong mimetypes for images
• Wrong mimetypes for JSON

JS/DOM

• (When Possible) identify the js lib used against a DB of the latest versions of JS libs. (to understand the use of legacy code)
• Identify, count how many times `navigator.userAgent` is used on the Web and a couple of other related thing.
• WebKitCSSMatrix usage See https://bugzilla.mozilla.org/show_bug.cgi?id=717722
• requestFullScreen vs requestFullscreen. See https://bugzilla.mozilla.org/show_bug.cgi?id=743198#c5
• window.getComputedStyle() see https://bugzilla.mozilla.org/show_bug.cgi?id=548397
• innerText is not available on Gecko but creates Web Compatibility issues such as Techcrunch webcompat

Video

• Ads before video and transition to video
• EME required
• List of video providers (stats for understanding if we need to focus our contacts actions toward some specific people)
• List of JS libraries used for video players
• Flash-only video (perhaps already covered in 1108668)
• Video dimensions
• Compressed video sample sizes
• Frame drops
• Hardware or software decoders
• Playing videos concurrently
• Audio speaker configuration e.g. mono, stereo, 5.1

Related information

h264 rec: http://www.itu.int/rec/T-REC-H.264-201402-I/en