Scale a clip to 1080p, 720p, 480p or any exact width and height you type. Lock the aspect ratio so nothing stretches, or fit-and-pad it into a new shape, real FFmpeg re-encoding with a live preview, right in your browser and never uploaded.
GigAI Video Resizer changes a video's frame size in your browser using ffmpeg compiled to WebAssembly, re-encoding to H.264 - nothing installs and nothing uploads. It's the right tool when a platform wants 1080×1920 or a form wants 720p. For file-SIZE reduction at the same dimensions, the Video Compressor does that.
The GigAI Video Resizer runs a full FFmpeg build compiled to WebAssembly directly inside your browser tab, so it can re-scale a video's resolution without ever sending your footage to a server. Downscaling is the everyday job: a 4K phone recording is overkill for a 720p upload cap, a 1080p screen capture is heavier than a support ticket needs, and an old device or embedded player only wants 480p. Drop your file and either tap a preset height (2160p, 1440p, 1080p, 720p, 480p, 360p) or type a custom width and height. Keep 'Lock aspect ratio' on and you only need one dimension: the other is computed for you and the encoder snaps it to an even number so H.264 stays happy. When your target shape differs from the source (say, squeezing a widescreen clip into a square slot), choose a fit mode: Contain letterboxes the whole picture with padding so nothing is cut, Cover fills the frame and trims the overflow, and Stretch forces the exact box even if it distorts. The tool transcodes to a broadly-compatible H.264/AAC MP4 (WebM stays WebM) with faststart for instant web playback, then hands you a preview player and the exact output size before you download. Because everything is client-side there's no upload wait and no privacy tradeoff: personal, confidential or unreleased footage never leaves your machine. Be honest with yourself about the engine: WebAssembly FFmpeg is meaningfully slower than a native app and it is memory-bound, so a short clip is quick while a large 4K source takes real time and a determinate progress bar keeps you posted. Close the tab and every byte is gone.
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Drag an MP4, MOV, WebM, MKV or other common video onto the workspace, or click to browse. It's read locally and you'll see its size, duration and current resolution immediately.
Tap a preset height or type a custom width and height. With the aspect ratio locked you only need one dimension, the other fills in automatically.
If your target isn't the source's shape, pick Contain, Cover or Stretch. The first run loads the FFmpeg engine once, a one-time moment.
Press Resize and watch the determinate progress bar. Play the preview to confirm it looks right, read the output size, then download, or reset and try another target.
Tap a standard height (2160p, 1440p, 1080p, 720p, 480p or 360p) or type your own width and height in pixels when you need to hit a precise box.
Leave the ratio locked and set just one dimension. The other is computed from your source so the picture never looks squashed or stretched. Unlock it only when you deliberately want a new shape.
When the target shape differs, choose Contain (letterbox, keep everything), Cover (fill the frame, trim the edges) or Stretch (force the exact box): each is explained inline so you pick with intent.
A full FFmpeg build compiled to WebAssembly rescales with the same libswscale filters desktop tools use, encodes H.264/AAC and even-snaps dimensions for you. No upload, no account, no install.
The resized result plays right in the page so you can confirm the framing, sharpness and any padding look right before you commit, the check a command line never gives you.
Rescaling happens on your device with a self-hosted engine. Personal recordings, unreleased footage and confidential captures are never uploaded, stored or logged.
Uploaders, ad networks, LMS players and embeds all have a max (or preferred) resolution. Downscale in one pass so your clip is accepted and plays smoothly instead of being rejected or re-encoded badly.
Fewer pixels means fewer bytes. Going 4K → 1080p or 1080p → 720p usually cuts the file size substantially on its own, which is often all you need before an upload or an email.
The aspect lock and the fit modes make distortion a deliberate choice, not a mistake. You always know whether the picture is padded, cropped or forced.
Server resizers make you upload the big file first and trust them with it. Here the video never leaves your browser, so there's no upload bar and nothing to trust.
From quick one-off fixes to daily workflows, see how people put this tool to use.
A shot-in-4K reel or a 1080p promo needs to be 720p for a size cap or a faster upload. Drop to the target height in one pass, aspect intact, and ship it.
A 4K screen capture of a repro is enormous. Scale it to 720p so it drops cleanly into a GitHub issue or a Jira ticket without blowing the attachment limit.
Legacy classroom hardware and embedded LMS players choke on high-res video. Downscale to 480p so it plays smoothly where the big file simply stutters.
Personal, medical or confidential recordings shouldn't be uploaded to a stranger's server just to change resolution. Do it entirely in your browser so nothing ever leaves the device.
Accepts MP4, MOV, WebM, MKV and AVI, and produces MP4 and WebM, all processed locally in your browser.
Compress video in your browser with FFmpeg, shrink MP4, MOV, WebM and MKV files with a simple quality slider, see the exact bytes and percentage saved next to a live preview, then download. Nothing is uploaded.
Crop video online in your browser, drag a box over a live preview or pick an aspect preset (1:1, 9:16, 4:5, 16:9) to reframe the picture, then download the cropped clip. No uploads, no account, no watermark.
Convert video between MP4, WebM, MOV, AVI, MKV and GIF in your browser with FFmpeg. Pick a target format, tune MP4 quality, preview the result and download. Nothing is uploaded.
Cut and trim video online in your browser, drag a visual timeline to set exact start and end points, preview the selection, and download the clip. No uploads, no account, no watermark.
Add a text or logo watermark to a video online, in your browser, position it in any corner or the centre, set the opacity, and download the branded clip. No uploads, no account, no second watermark of ours.
Mute a video online in your browser, remove the audio track, preview the silent result, and download it. MP4, MOV, WebM and MKV, no uploads, no account, no watermark, and the picture stays untouched.
Go deeper on the concepts behind the video resizer.
Hit a snag? Here are quick fixes for the issues people run into most.
That's the Contain fit padding your clip into a target shape that doesn't match the source. Switch to Cover to fill the frame (it trims the overflow instead), or leave the aspect ratio locked and set only one dimension so the output keeps the original shape and needs no padding.
You likely have the aspect lock off with a mismatched width/height, or you chose Stretch. Turn 'Lock aspect ratio' back on and set just one dimension, or pick Contain / Cover so the true proportions are preserved.
Expected. This is FFmpeg compiled to WebAssembly, which is slower than native and memory-bound, and rescaling a high-resolution source is heavy. Keep the tab focused, watch the progress bar, and for very large files trim the clip's length first or choose a smaller target.
WASM has a memory ceiling. Close other heavy tabs and retry. If it still fails the source is likely too large for in-browser encoding: shorten it first or start from a lower-resolution copy. As a loose guide, keep inputs under a few hundred MB.
Downscaling is what you almost always want: set a preset height at or below your source's and let the width follow automatically.
Keep 'Lock aspect ratio' on for the cleanest result. Only turn it off when you truly need to reshape the frame.
Choose Cover when you must fill an exact box and can lose a little from the edges. Choose Contain when nothing may be cut and padding is acceptable.
Upscaling (going higher than the source) won't add real detail. It just enlarges existing pixels, so expect softness.
The FFmpeg engine loads once per session on your first resize. After that, subsequent runs skip straight to encoding.
Recent updates and improvements to the video resizer.
Initial release, in-browser resolution scaling via self-hosted FFmpeg (WebAssembly), standard height presets, custom width/height, an aspect-ratio lock, a preview player and one-click download of a faststart MP4.
Added the three fit modes (Contain / Cover / Stretch) for changing a clip's shape, with inline explanations, plus automatic even-dimension snapping and a clearer one-time engine-loading state.
Refined the presets to compute width from the source when the ratio is locked, improved memory handling and honest guidance for large 4K files, and added drag-and-drop plus reset-and-retry to the workspace.
Your video is read and re-encoded entirely in your browser using a self-hosted FFmpeg (WebAssembly) engine. It is never uploaded to any server. Nothing is stored, logged or transmitted, so you can safely resize personal, confidential or unreleased footage. There's no upload step and no cloud copy. Close the tab and every byte is gone.
Free, private and instant. Video Resizer runs right in your browser.
