Trim video

Cut a clip without re-encoding it — lossless, and almost instant.

Drop a video here, or click to choose

MP4, MOV, WebM or MKV. The file is read straight from disk a few megabytes at a time, so its size does not really matter — nothing is uploaded and nothing is held whole in memory.

What lossless video trim is

Cutting a clip by copying already-compressed packets into a new container rather than decoding and re-encoding them. No decoder runs, no encoder runs, and the picture that comes out is the picture that went in. The cost is that a copy can only begin at a keyframe.

What this tool does that others do not

  • Nothing is decoded, so nothing is lost

    Most online trimmers decode to pictures, discard the frames outside your range and encode the rest again — which is why they take minutes, why the result is slightly softer, and why trimming twice makes it worse both times. A ten-second cut from a 1080p file here typically finishes in under a second, bounded by disk read speed rather than by encoding.

  • The real start is measured and shown

    Ask for a cut at 10.0 seconds on a file with keyframes every two seconds and the copy has to start at 8.0. Most tools round silently and hand you a clip that begins two seconds early, which reads as a broken trimmer rather than as a property of the format. As you move the start slider this one looks up the last keyframe at or before your point and prints the exact figure.

  • It works without a video encoder

    Because there is no encoder in the path, this runs on machines that have no usable video encoder at all — including browsers where every other video tool here has to refuse.

How to use it

  1. Drop in an MP4, MOV, WebM or MKV

    A QuickTime file comes out as MP4, because both are the same underlying format and MP4 plays everywhere.

  2. Set the range and read the printed start

    If the offset is larger than you can live with, nudge the start forward — a nearer keyframe is usually a fraction of a second away.

  3. Accept keyframe accuracy, or change tool

    If you need the cut frame-exact you need a re-encode, and a proper editor is the right place for that rather than a browser tab.

Worked example

Real input, real figures.

A cut that cannot land on the mark

You give it

Start at 10.0 seconds, keyframes every 2 seconds.

You get

The copy begins at 8.0 seconds and the tool says so before you commit. Sometimes the offset is zero, often a fraction of a second, occasionally the full two — it depends entirely on where the encoder put the keyframes.

Against an online trimmer

AspectThis toolAn uploading trimmer
MethodStream copy, no re-encodeDecode and re-encode
QualityIdentical to the sourceSlightly softer, cumulatively
Time for a 200 MB fileAbout as long as reading itUpload, then encode
Cut accuracyKeyframe, with the real start shownFrame, or rounded silently
Your fileNever sentUploaded and stored

Guide

What it will not do

  • MP4, MOV, WebM and MKV only. AVI, WMV, FLV, MPEG program streams and MXF are refused: the library that would read them is FFmpeg compiled to WebAssembly, whose core is GPL-licensed and whose build is 30.7 MiB — larger than the maximum single file this site’s host will serve.
  • A .mov holding ProRes or DNxHD is refused by name. No browser has ever shipped a decoder for either, so there is no client-side route at all. Export H.264 from your editor first.

Nothing is decoded, so nothing is lost

Most online trimmers decode your video to pictures, throw away the frames outside your range, and encode the rest again. That is why they take minutes, why the result looks slightly softer than the original, and why trimming the same clip twice makes it worse both times.

This one never touches a pixel. A video file is a container holding already-compressed packets, and cutting it to a range is a matter of copying the packets you want into a new container. No decoder runs, no encoder runs, and the picture that comes out is the picture that went in, byte for byte. A ten-second cut from a 1080p file typically finishes in under a second, and the time it takes is bounded by how fast your disk reads rather than by how fast your processor encodes.

A useful side effect: because there is no encoder in the path, this works on machines that have no usable video encoder at all — including Firefox on Android, where every other video tool on this site has to refuse.

The keyframe problem, stated rather than hidden

There is one real cost to the fast path, and it is worth understanding because every lossless trimmer has it. Compressed video is not a sequence of independent pictures. Most frames describe only what changed since the frame before, so they are meaningless without the run of frames that precedes them. Only a keyframe stands alone.

That means a copy can only begin at a keyframe. Ask for a cut at 10.0 seconds on a file with keyframes every two seconds and the copy has to start at 8.0. Most tools round silently and hand you a clip that begins two seconds early, which reads as a broken trimmer rather than as a property of the format.

So this tool asks the file. As you move the start slider it looks up the last keyframe at or before your point and prints the exact figure — sometimes zero, often a fraction of a second, occasionally the full two. Nudging the start forward a little will usually find a closer one. If you need the cut frame-exact, you need a re-encode, and you should reach for a proper editor rather than a browser tab.

Four containers, and why not more

MP4, MOV, WebM and MKV are read; a QuickTime file comes out as MP4, because both are the same underlying format and MP4 is the one that plays everywhere. AVI, WMV, FLV, MPEG program streams and MXF are refused, and the refusal is deliberate rather than a shortcoming waiting to be fixed.

The library that would read everything is FFmpeg compiled to WebAssembly. Its core is GPL-licensed — its build enables x264 and x265, both GPL, and sending that binary to your browser counts as distribution, which would oblige us to publish this entire site under the same terms. It is also 30.7 MiB, which is larger than the maximum single file our host will serve. Neither problem has a workaround, so rather than promise a converter that fails on half of what it is given, the tool takes the formats it can genuinely handle and says so on the page.

A .mov holding ProRes or DNxHD is refused by name for a different reason: no browser has ever shipped a decoder for either, so there is no client-side route at all. Export H.264 from your editor first. More in video & audio tools.