sizeunder

Compress an image

Get any photo under a size limit without sending it anywhere. Pick a target in kilobytes, drop one image or a batch, and download smaller files that never leave your device.

Files never leave your device Free · No signup · No watermark JPG · PNG · WebP

Compress to a target size

JPG, PNG, or WebP · processed on your device

Drop images hereor click to browse. Batch supported.JPG · PNG · WebPChoose imagesUp to 50 files · 50MB each · nothing is uploaded
Output format

How to compress an image

  1. Add your image Drop a file, choose one from your device, or paste from the clipboard.
  2. Set a target size Use the preset or enter your own limit in kilobytes.
  3. Download the result The tool returns the best quality that fits under the limit.

Compress to a size, not just a quality guess

Most compressors ask you to move a quality slider and hope for the best. SizeUnder works backwards from the result: enter 100KB, 200KB, 500KB, or any custom target, and the tool searches for the best quality that still fits.

If quality alone cannot get there, it reduces the dimensions step by step. You get a file that is actually under the limit, plus a clear message if the target is too small to reach without turning the image into a thumbnail.

One image or a whole batch

Drop a single file when you are in a hurry, or select a folder of images when a form only accepts small uploads. Each file is processed in the browser, with per-file status and a single ZIP download when the batch is done.

  • JPG, PNG, and WebP input
  • Keep the original format or switch to JPG/WebP
  • Transparent PNGs keep their transparency unless you choose JPG
  • No account, no queue, and no upload wait

Which output format should you choose?

For photographs, JPG or WebP usually gives the smallest file. WebP often saves another 20–35% at similar quality and is supported by every current browser. PNG is the right choice for logos, screenshots, and anything with transparency, but it does not compress photos as efficiently.

Frequently asked questions

Is SizeUnder really free?

Yes. There is no account, no payment, and no watermark. The tool runs in your browser, so there are no server costs to pass on.

Are my images uploaded to a server?

No. Your browser decodes, resizes, and encodes the image locally. The file is not sent to SizeUnder or to a third-party processing service.

Can I compress multiple images at once?

Yes. Select or drop several files, set one target for the batch, and download the successful results as a ZIP.

What happens if my target size is impossible?

The tool stops at a sensible minimum dimension and tells you the smallest size it could reach. It will not silently give you a file that is still over the limit.

Last updated: November 12, 2026