Accuracy and Disclaimer

Last updated 2026-08-13.

Use the results, but check them

KBSize is built to be accurate and is tested against known reference values. It is still software written by people, running in a browser we do not control, on input we cannot see. Treat every result as a well-informed starting point rather than an authority.

Before you rely on a result for anything that matters — money owed to someone, a legal or tax position, a medical decision, a machined part, a navigational fix — check it against a second source.

Specific limits of this site

Compression is lossy. Detail removed to reach a size target cannot be recovered from the result, so keep your original file. The site never touches it — the download is a new file made in your browser.

A size target is treated as a ceiling. The tool searches for the highest quality that still lands under the number you gave, so results are normally a little under it, never over.

Some targets are unreachable at the original dimensions. When that happens the tool says so and offers to reduce the dimensions instead of quietly handing back a file that the form you are fighting will reject again.

PNG is lossless and has no quality dial to trade against file size, so anything given a size target is re-encoded as JPEG. Transparency is flattened onto white in the process, which changes how the image looks on a coloured background.

Which files an upload form accepts, and how it measures their size, is decided by that form. Some count kilobytes as 1000 bytes rather than 1024; if a result is refused by a whisker, aim a little lower.

Not professional advice

Nothing on this site is legal, financial, medical or other professional advice, and using the image compressor does not create a professional relationship of any kind. If a decision has real consequences, ask somebody qualified and accountable.

Liability

Our liability for the results this site produces is limited as described in the Terms of Service. In short: the site is free, it is provided as-is, and we cannot accept responsibility for losses caused by relying on it without checking.