What does an image resizer change?

An image resizer changes pixel dimensions rather than merely altering how large an image appears in CSS. Reducing width and height can lower transfer and storage cost, while an aspect-ratio lock prevents stretching by calculating one dimension from the other.

The browser uses createImageBitmap and Canvas locally, exporting PNG for PNG input and JPEG at quality 0.92 otherwise. Upscaling cannot create missing detail and may look soft, while converting other formats to JPEG can remove transparency. Enter positive dimensions and keep the original for future sizes.