One video in, every social size out. 9:16 for Reels, TikTok and Shorts, plus 4:5, 1:1 and 16:9, with a blurred background, colour bars or a crop you aim yourself. Free, no watermark, nothing uploaded.
A single export almost never fits everywhere. Reels, TikTok and YouTube Shorts want a tall 9:16 frame. An Instagram feed post takes up the most screen at 4:5. Square 1:1 still travels well across older placements and ad sets. YouTube and Facebook video are 16:9. Doing that by hand means loading the same clip into an editor four times and re-exporting four times, which is precisely what the monthly resize tools charge for. This page reads your clip once and writes every size you tick during that same read.
Blurred background keeps every pixel of your original picture and fills the leftover space with a soft, slightly dimmed copy of the frame behind it. Nothing is lost, which makes it the safe choice when captions, a logo or a product sits near the edge of the frame. Colour bars do the same job with a flat colour instead, which looks deliberate when your brand already has a background colour. Crop to fill uses the whole frame with no bars at all, but it discards everything outside the new shape, so you get a nine cell grid to say which part of the picture must survive.
Everything runs inside your browser on your own machine, using the video encoder that is already built into it. The clip is stepped through frame by frame, each frame is drawn into one canvas per output size, and the result is encoded straight to H.264 video with AAC audio in an MP4. The audio is decoded and encoded once and then attached to every file, rather than re-encoded per size. Your video is never uploaded, so there is no queue and no question about where client footage ended up. The one size limit is your own machine: past roughly 700 MB the browser cannot decode the audio track, so a file that large comes out silent and the page warns you before you start. It needs a Chromium browser, meaning Chrome, Edge or Opera, because that is where the browser video encoder is available today.
This is a re-encode, so the output is compressed again from whatever you feed it. Start from the best copy you have rather than a version already squeezed down for WhatsApp. Cropping a wide clip into a tall frame is also an upscale by nature: the narrow strip you keep gets stretched to fill 1080 pixels across, so it will look softer than the original. That is true of every tool that does this, not just this one. Speed depends entirely on your hardware, and this is slow work: the clip is stepped through one frame at a time and every frame is drawn and encoded once per size, so expect several times the length of the clip, not a little over it. A one minute clip at four sizes is a few minutes of work, a ten minute clip is a coffee break. The progress bar shows a live estimate once encoding starts, and Cancel stops the job at the next frame. If your graphics chip refuses to run four encoders at the same time, the tool falls back to running them one after another, which is slower but produces identical files. Platform specs also change, so check the current requirement if a placement really matters to you.