Browser Video Crop & Time Stretch

Crop, trim and change the speed of any video right in your browser. Drag a crop box, time-stretch with pitch control, rotate, fade and export to MP4, WebM or MOV. 100% private — no uploads, all processing happens on your device.

Overview

This browser-based video editor lets you crop to any aspect ratio, trim with a filmstrip timeline, and time-stretch from 0.25x to 4x — all processed locally using FFmpeg compiled to WebAssembly. Unlike cloud editors, your video file never leaves your device: no upload, no account, no waiting for a server. Pitch preservation keeps voices sounding natural at any speed, and you can rotate, flip, fade, or mute before exporting to MP4, WebM, or MOV.

Key Features

  • Interactive crop box with aspect-ratio presets
  • Filmstrip timeline with trim handles and scrubbing
  • Time-stretch from 0.25x to 4x with pitch control
  • Rotate, flip, mute, volume and fade
  • Export to MP4, WebM or MOV with quality presets
  • 100% client-side processing with FFmpeg WebAssembly

Common Use Cases

  • Reframe for Social Media — Crop landscape footage to 9:16 or 1:1 with locked aspect-ratio presets for Instagram Reels, TikTok, or YouTube Shorts without re-uploading anywhere.
  • Create Slow-Motion Clips — Time-stretch any segment to 0.25x–0.5x with pitch preservation so the audio still sounds natural in your slow-motion highlight reel.
  • Speed Up Tutorials — Stretch a long screen recording to 2x–4x speed to produce a condensed walkthrough, then trim the silent gaps from the filmstrip timeline.
  • Remove Unwanted Portions — Use the trim handles to cut a precise start and end point from a longer video before sharing, keeping only the take you want.
  • Confidential Footage Editing — Edit sensitive HR interviews, medical recordings, or private family videos locally — nothing is transmitted to any server at any point.

How It Works
1

Import Your Video

Drag & drop a video or pick a file. MP4, MOV, WebM, MKV and AVI are supported. Nothing is uploaded — your file stays on your device.

2

Crop, Trim & Adjust Speed

Drag the crop box, set start/end points on the filmstrip timeline, change the playback speed (with optional pitch preservation), then rotate, fade or mute as needed.

3

Export & Download

Pick a format and quality and the edit is rendered locally with FFmpeg WebAssembly. Download the finished video when it's ready.

Frequently Asked Questions

Are my videos uploaded to a server?
No. All editing and exporting runs entirely in your browser using FFmpeg compiled to WebAssembly. Your video never leaves your device, which keeps it completely private.

Which video formats can I import and export?
You can import common formats such as MP4, MOV, WebM, MKV and AVI. Exports are available as MP4 (recommended, fastest and most compatible), WebM and MOV.

How does time-stretching work?
Pick a speed from 0.25x up to 4x, or type a target duration and we calculate the speed for you. By default audio pitch is preserved so voices still sound natural; you can also let the pitch change with the speed for a classic fast/slow effect.

Can I crop to a specific aspect ratio?
Yes. Use the freeform crop box or lock it to presets like 1:1, 4:5, 9:16, 16:9 and 21:9. The output resolution updates live as you resize.

Is there a file size limit?
Because everything runs in your browser's memory, very large files can be slow or run out of memory. We recommend videos up to about 300MB for a smooth experience.

Why is exporting to WebM slower than MP4?
WebM uses the VP9 encoder which is significantly slower in WebAssembly than the H.264 encoder used for MP4. For the fastest exports with the widest device compatibility, choose MP4.

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