Trim Video Online — Cut MP4 & MOV Clips Without Uploading

Near-instant clip trimming and crisp GIF export, entirely in your browser.

Cutting a clip out of an MP4 doesn't have to mean re-encoding it. This tool demuxes the actual container with mp4box, finds the nearest keyframe before your chosen start point, and copies the compressed sample bytes straight through into a new file — a stream-copy trim that finishes in a fraction of a second and loses no quality, with a separate re-encode path reserved for operations that genuinely require decoding every frame.

How to trim a video in your browser

  1. Drop an MP4, MOV or M4V file onto the upload area, or click it to pick one from your device.
  2. Drag the Start and End sliders until the selected duration covers only the part you want to keep.
  3. Pick the export: "Trim MP4" for an instant, keyframe-aligned cut that copies the picture untouched but leaves the sound out, or "Edit MP4" for a frame-exact re-encode that keeps the audio as AAC.
  4. Press the export button and save the finished MP4 with the download link that appears underneath.

Which trim mode keeps the sound

The two MP4 exports treat audio differently, and the button labels say so. "Export trimmed MP4 (no audio)" is the lossless path: it remuxes the video track alone, so the result is silent even when your source has sound. Choose it when you only need the picture and want zero quality loss.

"Export edited MP4" goes through the re-encode pipeline, which decodes the source audio, cuts it to the same start and end, and encodes it again as AAC at 128 kbps before muxing it next to the new H.264 picture. If the file has no readable audio track, or the browser lacks an AudioEncoder, you still get a valid MP4 — just without sound.

Lossless trim means keyframe-aligned, not frame-exact

A compressed video stream can't be cut at an arbitrary frame without decoding, since most frames after the first in a group of pictures are deltas against a preceding keyframe. The lossless path scans the sample table for the nearest sync sample at or before your start time, keeps every sample through the last one before your end time, then rebuilds a standalone MP4 with timing rebased to zero. Your trim's actual start may land slightly earlier than what you dragged to, right at that keyframe — the tradeoff for finishing in milliseconds.

Because this path only copies compressed bytes — never touching a VideoDecoder or VideoEncoder — the kept picture data is bit-for-bit identical to the source. The audio track, when present, isn't part of this path: only video samples are trimmed here, disclosed in the interface rather than silently dropped.

The re-encode path: rotate, filter, caption, keep the audio

Rotating, filtering, or burning in caption text requires decoding real pixels, so the Edit MP4 mode runs through a different pipeline: every sample in range is decoded with WebCodecs' VideoDecoder, each frame is drawn onto an OffscreenCanvas through rotation, filter and caption steps in fixed order, then re-encoded into H.264 at a 6 Mbps target. Only frames that overlap your selected range are written, which is why this export starts exactly where you dragged rather than at a keyframe. The source audio is decoded and re-encoded to AAC alongside the new video track.

The seven pixel filters — grayscale, sepia, brightness, contrast, saturation, a box blur, and a radial vignette — are plain per-pixel math over ImageData, applied in a fixed order so combinations stay predictable.

Trim video formats, file size and free limits

Hardware encode, software encode, or no encode at all

Before showing re-encode controls, the tool probes the browser's WebCodecs implementation with a representative H.264 config — hardware first, then re-probing with a software preference, since a device can fail both and claiming software works without testing it would be a guess dressed up as fact. The result is one of three disclosed states: hardware-accelerated, software-only, or no encode support. With no encoder, lossless trim still works, and GIF export still works as long as the browser can decode video, but the Edit MP4 re-encode is unavailable.

GIF export uses a real two-pass palette, not per-frame guessing

Exporting a GIF decodes every frame in range the same way re-encode does, then hands the RGBA frames to gifenc's two-pass workflow: a first pass samples up to 30 evenly-spaced frames into one shared palette, and a second pass maps every frame onto that fixed palette before streaming to the encoder. One global palette keeps colors from flickering between frames. Palette mode trades quality for size: 256 colors is GIF's own ceiling, while a 64-color mode accepts banding for a smaller file.

A memory ceiling, disclosed up front

Files above roughly 500MB are flagged before you start: in-browser video processing runs into a real ceiling around 2GB of heap, with source, working, and output copies potentially all resident at once — so a file under that size on disk can still exhaust memory mid-operation, especially during re-encode or GIF export.

Your clip is trimmed on this device, not on a server

Many online trimmers ask you to upload the whole recording, wait in a queue, and then trust a promise that the copy gets deleted after a few hours. Here the file is opened straight from your disk, demuxed and cut inside the browser tab, and handed back as a download link, so there is no upload wait, no server copy, and nothing left behind to delete.

When to reach for something else

Questions people ask about Video Trimmer & GIF Maker

Why does my trimmed clip start slightly before the point I selected?
Lossless trim can only cut at a keyframe, since frames in between are stored as deltas against one. The tool finds the nearest keyframe at or before your chosen start point and cuts there, which can be a fraction of a second earlier than the exact point you dragged to — the tradeoff for a trim that finishes instantly with no quality loss.
Why is there no audio on my trimmed video?
You most likely used the lossless "Trim MP4" export, which copies the video track only and is labelled "(no audio)" for that reason. Switch to "Edit MP4" and export again: that path decodes the source audio and re-encodes it to AAC next to the video. A source with no readable audio still comes out silent.
Does the trimmed video have a watermark?
No. Neither the lossless trim, the Edit MP4 re-encode nor the GIF export adds a logo or text of any kind. The only overlay that can appear is caption text you type yourself in the Edit MP4 panel, and the free tier limits clip length, never picture quality.
What video formats can I trim?
The picker accepts MP4, MOV and M4V files. They are parsed as MP4-family containers, so a file in another container such as WebM or MKV cannot be trimmed here. H.264 video is recommended because it is the codec browsers decode most reliably for the re-encode and GIF exports.
Is my video uploaded to a server?
No. The file is read from your disk into the browser tab, cut or re-encoded there, and offered back as a local download link. The page makes no network request carrying your footage, so there is no server copy to wait for or to worry about deleting.
Can I remove a section from the middle of a video?
Not in one step. This tool keeps a single continuous range between the start and end points you set, so removing a middle stretch means exporting the part before it and the part after it as two separate files. It cannot join those two pieces back together.
What is the difference between trimming and cutting a video?
Trimming usually means shortening a clip from its ends, keeping one continuous piece; cutting often means splitting a video or deleting a stretch in the middle. This tool trims: you choose one start and one end, and everything outside that range is left out of the export.
Can I trim a video on my phone?
It depends on the mobile browser rather than the device. The lossless trim only needs the browser to open the MP4 and read its data, while the Edit MP4 re-encode needs WebCodecs video encoding and GIF export needs WebCodecs decoding. The page checks encoding support on load and tells you which exports are available.
What does 'software encoding only' mean and should I worry about it?
It means your browser can encode H.264 via WebCodecs but without hardware acceleration, so re-encoding will work but run slower, and very long clips may take a while. It's determined by an actual encoder probe on page load, not a guess based on your device model.
How big a video file can this handle?
Files above roughly 500MB are flagged as a risk before you proceed, because in-browser video processing has a real memory ceiling near 2GB and multiple copies of frame data can be resident at once during re-encoding. Lossless trim, which never decodes frames, handles larger files more comfortably than re-encode or GIF export do.
Does GIF export produce the same quality as the original video?
No format that caps at 256 simultaneous colors can match full video color depth. The max-quality palette mode uses that full 256-color ceiling — the best GIF itself can do — while the smaller-file mode drops to 64 colors and accepts visible banding for a smaller download.

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Content reviewed 2026-09-27.