Browsers expose three separate APIs for codec support, and they return different answers for the same codec on the same device. One says yes, another says no, a third says yes but not efficiently. Media servers like Jellyfin, Plex, and Emby pick one of these APIs to decide whether to direct-play or transcode — and often pick wrong.
CodecProbe tests 77 codecs (HEVC, AV1, Dolby Vision, VP9) against all three APIs and shows the results side-by-side. When the badges disagree, you've found the gap between what your device reports and what it can actually do.
Each codec card includes education content explaining what a string like hvc1.2.4.L153.B0 actually means, field by field, with spec references.
Zero runtime dependencies, entirely client-side, works offline as a PWA.
The test matrix is validated by codec-resolve [1], a companion Python tool that resolves, decodes, and cross-validates codec strings for 6 video codec families (HEVC, AV1, VP9, AVC/H.264, VP8, Dolby Vision). 180 tests, zero dependencies.
Both projects are AGPL-3.0. Looking for contributors — especially for VVC/H.266, audio codecs (AAC, Opus, DTS, Dolby), and platform-specific quirks on webOS, Tizen, or Roku.