Private video resizer
Private Video Resizer that runs on your laptop, not in the cloud
Resizing video usually means picking up a file, sending it to a cloud service for re-encoding, and waiting for it to come back. That model treats your footage as a payload to ship. For sensitive content this is the wrong shape: anything sent for re-encoding sits, however briefly, on someone else's infrastructure.
Try it now
The resize tool runs the same browser-local engine described on this page.
Why this matters
The Resize tool here re-encodes inside the browser tab. The browser reads the source bytes off your disk, FFmpeg compiled to WebAssembly produces the new dimensions, and the result is written back to your downloads folder. The intermediate frames stay in browser memory and clear when you close the tab.
The practical effect is that the privacy concern goes away because the transfer goes away. Not "encrypted in transit, deleted within 24 hours", but the much simpler "never transferred."
What you actually get
No upload of the source file
The video stays in browser memory throughout the resize operation. The Network tab of DevTools shows zero outbound requests for your media.
Any aspect ratio, no menu of approved sizes
Width and height can be anything FFmpeg accepts. Standard social presets are available; arbitrary custom sizes work too. No server-side aspect-ratio whitelist.
No watermark on the output
The free tier is the only tier. The resized MP4 contains your video at the new dimensions and nothing else.
Letterbox and crop modes
Choose how the resize handles aspect-ratio mismatches: letterbox to preserve content, or crop to fill the frame. Both run locally.
How to resize a video privately
01 Open the Resize tool
Click the Open button below. The Resize page loads with FFmpeg WebAssembly ready in your browser.
02 Drop your video
Drag the source file onto the upload area. The browser reads the bytes locally; nothing uploads.
03 Pick a target size
Choose a platform preset (TikTok, Reels, Shorts, etc.) or type a custom width and height.
04 Download the result
Click Resize and wait for the local re-encode. The new MP4 lands in your downloads folder.
Frequently asked questions
How does private resizing differ from a normal online resizer?
Normal online resizers upload the file to a server, re-encode it there, and send the result back. This page does the re-encoding in your browser tab against FFmpeg WebAssembly, so the upload step is skipped. The same H.264 MP4 comes out at the end, just without ever leaving your machine.
Are there file-size limits?
No imposed cap. The practical limit is your device memory and how long you are willing to wait. A modern laptop handles 1080p resize jobs up to about an hour comfortably; 4K starts to feel slow above ten minutes of input.
Does it support the same aspect ratios as the platform presets?
Yes. TikTok, Reels, Shorts, LinkedIn, and the rest are all available as one-click presets. Custom dimensions work for anything those presets do not cover.
Will the output play on every platform?
The encoder uses H.264 video and AAC audio inside an MP4 container, which is the combination that uploads cleanly to every social platform and plays on every modern device.
What happens to the source file when I close the tab?
Nothing persists past the tab session. The browser releases the in-memory buffers and the temporary OPFS scratch space (if any was used for large files) clears on the next browser cache cleanup.
Related Tools and Resources
Resize Video
The actual resize tool, with all platform presets.
Resize, No Upload
Same architecture, framed for the no-upload angle.
Offline Video Resizer
Same architecture, framed for the offline-after-first-load angle.
Private Video Editor
Full editor with the same browser-local model.