Sorting Formats
You can change the criteria for being considered the best by using -S (--format-sort). The general format for this is --format-sort field1,field2....
Available Sort Fields
The available fields are:
hasvid: Gives priority to formats that have a video streamhasaud: Gives priority to formats that have an audio streamie_pref: The format preferencelang: The language preference as determined by the extractor (e.g. original language preferred over audio description)quality: The quality of the formatsource: The preference of the sourceproto: Protocol used for download (https/ftps>http/ftp>m3u8_native/m3u8>http_dash_segments>websocket_frag>mms/rtsp>f4f/f4m)vcodec: Video Codec (av01>vp9.2>vp9>h265>h264>vp8>h263>theora> other)acodec: Audio Codec (flac/alac>wav/aiff>opus>vorbis>aac>mp4a>mp3>ac4>eac3>ac3>dts> other)codec: Equivalent tovcodec,acodecvext: Video Extension (mp4>mov>webm>flv> other). If--prefer-free-formatsis used,webmis preferred.aext: Audio Extension (m4a>aac>mp3>ogg>opus>webm> other). If--prefer-free-formatsis used, the order changes toogg>opus>webm>mp3>m4a>aacext: Equivalent tovext,aextfilesize: Exact filesize, if known in advancefs_approx: Approximate filesizesize: Exact filesize if available, otherwise approximate filesizeheight: Height of videowidth: Width of videores: Video resolution, calculated as the smallest dimension.fps: Framerate of videohdr: The dynamic range of the video (DV>HDR12>HDR10+>HDR10>HLG>SDR)channels: The number of audio channelstbr: Total average bitrate in kbpsvbr: Average video bitrate in kbpsabr: Average audio bitrate in kbpsbr: Average bitrate in kbps,tbr/vbr/abrasr: Audio sample rate in Hz
Sort Order and Modifiers
All fields, unless specified otherwise, are sorted in descending order. To reverse this, prefix the field with a +. E.g. +res prefers format with the smallest resolution. Additionally, you can suffix a preferred value for the fields, separated by a :. E.g. res:720 prefers larger videos, but no larger than 720p and the smallest video if there are no videos less than 720p.
For codec and ext, you can provide two preferred values, the first for video and the second for audio. E.g. +codec:avc:m4a (equivalent to +vcodec:avc,+acodec:m4a) sets the video codec preference to h264 > h265 > vp9 > vp9.2 > av01 > vp8 > h263 > theora and audio codec preference to mp4a > aac > vorbis > opus > mp3 > ac3 > dts.
You can also make the sorting prefer the nearest values to the provided by using ~ as the delimiter. E.g. filesize~1G prefers the format with filesize closest to 1 GiB.
Priority and Default Order
The fields hasvid and ie_pref are always given highest priority in sorting, irrespective of the user-defined order. This behavior can be changed by using --format-sort-force. Apart from these, the default order used is: lang,quality,res,fps,hdr:12,vcodec,channels,acodec,size,br,asr,proto,ext,hasaud,source,id. The extractors may override this default order, but they cannot override the user-provided order.
Note that the default for hdr is hdr:12; i.e. Dolby Vision is not preferred. This choice was made since DV formats are not yet fully compatible with most devices. This may be changed in the future.
If your format selector is worst, the last item is selected after sorting. This means it will select the format that is worst in all respects. Most of the time, what you actually want is the video with the smallest filesize instead. So it is generally better to use -f best -S +size,+br,+res,+fps.
Tip: You can use the -v -F to see how the formats have been sorted (worst to best).