Firefox WebRTC 2025
In an increasingly siloed internet landscape, WebRTC directly connects human voices and faces. The technology powers Audio/Video calling, conferencing, live streaming, telehealth, and more. We strive to make Firefox the client that best serves humans during those experiences.
Expanding Simulcast Support
Simulcast allows a single WebRTC video to be simultaneously transmitted at differing qualities. Some codecs can efficiently encode the streams simultaneously. Each viewer can receive the video stream that gives them the best experience for their viewing situation, whether that be using a phone with a small screen and shaky cellular link, or a desktop with a large screen and wired broadband connection. While Firefox has supported a more limited set of simulcast scenarios for some time, this year we put a lot of effort into making sure that even more of our users using even more services can get those great experiences.
We have added simulcast capabilities for H.264 and AV1. This along with adding support for the dependency descriptor header (and H.264 support), increases the number of services that can take advantage of simulcast while using Firefox.
Codec Support
Dovetailing the simulcast support, we now support more codecs doing more things on more platforms! This includes turning on AV1 support by default, and adding temporal layer support for H.264. Additionally there were a number of behind the scenes changes made. For our users, this means that they have a more uniform experience across devices.
Media Capture
We have improved camera resolution and frame-rate adaptation on all platforms, as well as OS-integrated improved screen capture on macOS. Users will have a smoother experience when joining calls with streams that are better suited to their devices. This means having smoother video and a consistent aspect ratio.
DataChannel
Improving reliability, performance, and compatibility of our DataChannel implementation has been a focus this year. DataChannels can now be run on workers keeping data processing off of the main thread. This was enabled by a major refactoring effort, migrating our implementation to dcsctp.
Web Compatibility
We targeted a number of areas where we could improve compatibility with the broad web of services that our users rely on.
Bug 1329847 Implement RTCDegradationPreference related functions
Bug 1894137 Implement RTCRtpEncodingParameters.codec
Bug 1371391 Implement remaining mandatory fields in RTCIceCandidatePairStats
Bug 1525241 Implement RTCCertificate.getFingerprints method
Bug 1835077 Support RTCEncodedAudioFrameMetadata.contributingSources
Bug 1972657 SendKeyFrameRequest Should Not Reject Based on Transceiver State
Summary
2025 has been an exciting and busy year for WebRTC in Firefox. We have broadly improved web compatibility throughout the WebRTC technology stack, and we are looking forward to another impactful year in 2026.
