YouTube upload color space: BT.709 for SDR, and Sume trim output

For SDR uploads YouTube recommends BT.709 as the color space. Sume's trim and probe docs do not describe a color-space setting or report, so tag the file yourself, and confirm the result with ffprobe before you upload.

YouTube facts are from its recommended upload encoding settings page (undated; read 2026-10-01). Sume facts are from the Video trim and Video inspect docs.

What does YouTube recommend for SDR color?

The page recommends BT.709 for SDR, and lists its transfer characteristics, color primaries and matrix coefficients as BT.709 (H.273 value 1). It says YouTube standardizes functionally similar matrices and primaries before processing: BT.601 and BT.709 TRC are identical and unified to BT.709, and BT.601 NTSC and PAL are unified to BT.601 NTSC. If the upload has an unspecified TRC, YouTube assumes BT.709.

What does Sume trim do to color?

Exact mode is a frame-accurate re-encode with libx264 and yuv420p. That is the pixel format; the docs do not say which color tags the output carries. The program table has no color-space field, and the server compiles ffmpeg itself, so raw fields such as vf, filter, codec or crf return ffmpeg_fields_rejected. Keyframe mode is a stream copy, so the source's own tags would stay.

How do I check the tags before uploading?

Download the trim result and read its stream tags. An empty or unknown value means the file leaves the color description unspecified, which is the case where YouTube assumes BT.709 for the transfer function.

ffprobe -v error -select_streams v:0 \
  -show_entries stream=color_space,color_transfer,color_primaries \
  -of default=noprint_wrappers=1 trimmed.mp4

What if my source is HDR or a different standard?

Tone-map before you hand the clip to Sume, since there is no color knob on trim. The page snapshot used here stops after the SDR table, so it does not tell me what YouTube does with other color spaces; read the full page for those rows. A related walk-through is Spotify's HDR upload tone-mapped to SDR.