Browser Video Crop & Time Stretch

Overview

Crop a video to any aspect ratio, trim it on a filmstrip timeline, and speed it up or slow it down from 0.25x to 4x. Pitch stays natural at any speed, and you can rotate, flip, fade or mute before exporting to MP4, WebM or MOV. FFmpeg runs in your browser, so your video never leaves your computer.

Reframe for social mediaCrop landscape footage to 9:16 or 1:1 for Reels, TikTok or YouTube Shorts.
Make slow-motion clipsSlow a moment down to 0.25x–0.5x while the audio still sounds natural.
Speed up tutorialsPlay a long screen recording at 2x–4x and trim the dead time.
Cut out the extrasSet an exact start and end so only the take you want is left.
Private footageEdit HR interviews, medical recordings or family videos without sending them anywhere.

Key features

Crop box with aspect-ratio presets
Filmstrip timeline with trim handles
Speed from 0.25x to 4x, with pitch control
Rotate, flip, mute, volume and fade
Export to MP4, WebM or MOV
Runs locally with FFmpeg WebAssembly

Guides

01 How to trim, crop or change the speed of a video

Set

Video Tools 08

Neighbours

01 Extract Audio from Video 02 Compress Video 03 HLS Stream Generator 04 Video & Audio Viewer 05 Photobooth 06 Screen Recorder

Specification

Command: video.video_crop_time_stretch
Set: Video
Input: MIXED
Output: MIXED
Max file: 300MB
Batch: single file

MP4 QUICKTIME WEBM X-MATROSKA X-MSVIDEO

Runtime

Engine: ffmpeg-wasm 0.12
Threads: — workers
Isolated: —
WebGPU: —
Memory: —

Transport 0 B

Your file is opened, worked on and saved inside this tab. This tool has no upload step, so your file has nowhere else to go.

Keys

Search: ⌘K
Panels: ⌘1 · ⌘2
Full width: F
All keys: ⌘/

How it works

Open your video

Drop a video or pick a file. MP4, MOV, WebM and MKV open right away; formats your browser can't play, like AVI or WMV, get a quick preview copy first.

Crop, trim and set speed

Drag the crop box, set start and end on the timeline, pick a speed, then rotate, fade or mute if you need to.

Export

Choose a format and quality, and FFmpeg renders the video on your computer.

Frequently asked

Are my videos uploaded to a server?

No. Editing and exporting run in your browser with FFmpeg compiled to WebAssembly, so your video never leaves your device.

Which video formats can I import and export?

You can open MP4, MOV, WebM, MKV, AVI, WMV, FLV, MPEG-TS, MPG, OGV, MXF and most other formats. If your browser can't play one, the tool makes a preview copy, but the export always uses your original file. You can export to MP4 (fastest and most compatible), WebM or MOV.

How does time-stretching work?

Pick a speed from 0.25x to 4x, or type the length you want and the tool works out the speed. Pitch is kept by default so voices sound natural, or you can let it change with the speed.

Can I crop to a specific aspect ratio?

Yes. Crop freely or lock the box to 1:1, 4:5, 9:16, 16:9 or 21:9. The output resolution updates as you resize.

Is there a file size limit?

Everything runs in your browser's memory, so very large files can be slow or fail. Videos up to about 300 MB work best.

Why is exporting to WebM slower than MP4?

WebM uses the VP8 encoder, which is slower in WebAssembly than the H.264 encoder behind MP4. Choose MP4 for the fastest export that plays everywhere.

Keys

Search: ⌘K
Panels: ⌘1 · ⌘2
Full width: F
All keys: ⌘/