VideoTrim
Trim, mute or take the sound out of a video
The picture is never re-encoded. The frames you keep are copied across exactly as they were, so a trimmed clip is not a lower-quality copy of your video — it is the same frames in a smaller file. MP4 and MOV, in the tab you are looking at.
MP4 and MOV only. WebM and Matroska store their index in a different format entirely and are refused by name rather than failing oddly.
Cut, mute or extract the audio from an MP4 or MOV without re-encoding it. Turning a clip into a GIF is the one thing this page cannot do, because that genuinely needs decoding — it is not offered rather than offered badly.