Trim a video online: keep one part, drop the rest

How to trim a video in your browser

1. 01

   Open the file

   Drag an MP4, MOV, MKV, WebM or AVI onto the drop zone above, or click it and pick the file. It is read straight off your disk into the browser tab; nothing is transmitted.

2. 02

   Mark the part you want to keep

   Scrub to where the good part starts, right-click the timeline and add an edit, then drag the handles until the band covers exactly the section you are keeping. With the band active, press I to set its start to the playhead and O to set its end.

3. 03

   Press "Keep only this part"

   Every edit card has this button. It turns your marked range into two cuts — one covering everything before it, one covering everything after — so the range you marked is the only thing that survives.

4. 04

   Check the estimated duration

   The readout below the timeline shows the source length and the length after the trim. It should read the length of the section you kept.

5. 05

   Press Apply All Edits

   Both cuts become one filter graph and the video is encoded once. The first run downloads the ~32 MB engine, which is cached afterwards. The finished file appears as a download link.

The manual way: two cuts

"Keep only this part" is a shortcut for something you can also do by hand, and it helps to know what it produces. The editor's basic operation is a cut — a range that is removed. Keeping one section is therefore two cuts: one from 0 to the start of your section, one from the end of your section to the end of the timeline. Add them yourself and the result is identical; the button just saves you setting four handles instead of two and guarantees the two cuts butt up against your range exactly.

Either way, what you press at the end is Apply All Edits. Everything on the timeline is turned into a single FFmpeg filter graph and the video is encoded once, no matter how many cuts are stacked.

Trimming the start, the end, or both

Setting in and out points precisely

Three ways to place a boundary, from coarse to fine. Drag the band's handles on the timeline for a rough placement. Type a value into the Start or End field on the edit card for an exact one — seconds with decimals are accepted. Or use the keyboard the way an editing application does: park the playhead where the boundary belongs, using the player's own controls to step to the right moment, and press I to move the active range's start there or O to move its end.

As the handles move, the estimated duration below the timeline updates — source length on the left, finished length on the right, with the number of edits it accounts for. It is an estimate because it is computed from timestamps rather than by encoding, but for cuts it is accurate to a frame.

Frame accuracy versus keyframe snapping

There are two ways to trim a video, and they trade against each other. A lossless trim copies the compressed stream without decoding it, which means it can only start at a keyframe — the self-contained frames the encoder writes every second or two, or on a screen recording every ten seconds or more. Ask for 1:23.4 and you get the nearest keyframe, which may be several seconds off.

A frame-accurate trim, which is what this page does, decodes the video, keeps exactly the frames you asked for with FFmpeg's trim filter, and re-encodes the result with libx264 at the ultrafast preset and CRF 28. It lands where you put it, and it costs one generation of lossy compression — not visible on ordinary footage, but real. Trimming without losing quality works through that trade, and the FFmpeg guide has the -c copy command for when a keyframe cut is good enough and you have FFmpeg installed. How it works covers the full pipeline.

Trim, cut, or trim to a length?

Three pages on this site do closely related things with the same timeline, and the difference is what you are working towards.

• This page — keep one section

  You know which part is good. Mark it, keep it, drop the rest.

• Cut a section out — remove the middle

  You know which part is bad. Mark it, remove it, and the parts on either side are joined together. Stack as many as you need.

• Trim to a length — hit a number

  You are working towards a duration limit rather than a feel. Uses the estimated-duration readout as the target, and covers speeding a passage up when there is nothing left to cut.

They are all the same tool underneath. Whatever page you start on, the full editor is there, and speed changes, muting, a resolution cap and a container change can all ride along in the same encode.

Trimming MP4, MOV, MKV, WebM and AVI

FFmpeg demuxes all five, so a trim works the same on an iPhone MOV, an OBS MKV and an old AVI. The one difference is the preview: the scrubbable player is your browser's own video element, and browsers generally will not play MKV or AVI. On those files the trim still works — you place the boundaries with the time fields instead of by eye, or convert to MP4 first and trim the copy. The output container is your choice; MP4 with H.264 and AAC is the right default, and the formats page explains the others.

Questions about trimming video online