Free · no signup · never uploaded
Trim Video
Cut a clip down to the part you want — fast, lossless, and never uploaded.
Drop a video here or choose a file
or drop your file here.
MP4 · MOV · MKV — trimmed in your browser, never uploaded
Runs in your browser — your file is never uploaded.
Short answer
To trim a video, drop it below, set a start and end time, and download the cut. It copies the existing streams instead of re-encoding, so it is fast and lossless — and runs entirely in your browser, so nothing is uploaded.
Guides
Why trimming is instant when compressing is slow
Trimming here uses a stream copy: the existing compressed video and audio are copied straight into a new container, and nothing is decoded or re-encoded. That’s why a 300 MB file trims in seconds while compressing the same file takes minutes — and why the trimmed section keeps exactly the original quality, with no generational loss at all.
Why the cut may land slightly off your start time
Video is stored as occasional complete frames (keyframes) plus many frames that only describe what changed since. A stream copy can only start at a keyframe, because a partial frame is meaningless on its own. So your start time snaps to the nearest keyframe before it — usually within a second or two. That is the price of a lossless, instant cut; frame-exact trimming requires a full re-encode.
Video formats to MP4 — what happens to your file
| Input format | Usual codecs inside | Conversion | Max file size |
|---|---|---|---|
| MOV (QuickTime) | H.264 + AAC | Rewrap (lossless) | 500 MB |
| MKV (Matroska) | H.264 + AAC | Rewrap (lossless) | 500 MB |
| WebM | VP8/VP9 + Opus | Re-encode to H.264 | 100 MB |
| AVI | MPEG-4/DivX | Re-encode to H.264 | 100 MB |
| GIF | Animated GIF | Re-encode to H.264 | 200 MB |
A rewrap copies the existing video and audio streams into an MP4 container untouched — it is lossless and finishes in seconds. A re-encode decodes and re-compresses, so it takes longer and loses a little quality. Size caps differ because everything runs on one thread in your browser.
How the trim works
Everything happens locally in your browser with ffmpeg — here is exactly how:
- Load the engine. ffmpeg compiled to WebAssembly loads once from this site — your file is never uploaded.
- Read the duration. your browser reads the clip’s length locally so the start and end times can be validated before any work starts.
- Copy the selected range. ffmpeg seeks to your start point and copies the existing video and audio streams (-c copy) up to your end point, decoding nothing.
- Fix up the container. timestamps are rebased (-avoid_negative_ts make_zero) and the moov atom moved to the front so the trimmed file plays correctly everywhere.
Assumptions
- Everything runs client-side; trimming is fast because no re-encoding happens.
- Cuts land on keyframes, so the start can be up to a couple of seconds early.
- Quality is identical to the source — a stream copy is lossless.
Last reviewed: July 19, 2026
Frequently asked questions
How do I trim a video?+
Drop your video in above, enter the start and end time in seconds, and download the trimmed clip. It runs entirely in your browser and takes only seconds because nothing is re-encoded.
Are my videos uploaded to a server?+
No. Everything runs 100% in your browser using ffmpeg compiled to WebAssembly, so your file never leaves your device. Nothing is uploaded, stored, or sent anywhere — and once the converter has loaded it even works offline.
Does trimming reduce quality?+
No. The tool copies the original compressed streams rather than re-encoding them, so the part you keep is bit-for-bit the same quality as the source.
Why did my clip start a moment earlier than I asked?+
A lossless cut can only begin at a keyframe, so the start snaps back to the nearest one — typically within a second or two. Frame-exact cutting would require re-encoding the whole clip.
Why is the first conversion slower?+
The first time, your browser downloads the ffmpeg engine (about 31 MB) and starts it up. That happens once — later conversions reuse the loaded engine and are much faster.
Can I trim a large file?+
Yes — because trimming does not re-encode, it handles much larger files than the compressor or cropper, up to 500 MB.
Related tools
Video is processed entirely in your browser with ffmpeg and never uploaded.