Image Compression and Format Choice
Compression re-encodes an image to change its file size. A smaller file is not automatically the better result: compare the format, transparency, and visual quality together.
Compression means re-encoding the original
For web pages or email attachments, a smaller file can reduce transfer size. Re-encoding can also change how the image looks, so inspect the preview alongside the actual output size.
A source that is already efficiently compressed can become larger if you save it at high quality or use a different codec. Compression does not guarantee a smaller result. Check Utilook's size comparison and the downloaded file before deciding which version to use.
When to choose JPEG or WebP
JPEG is worth trying first for photographs and other images with gradual color changes. It cannot preserve transparency. For JPEG output, Utilook fills transparent areas with white before encoding.
Try WebP when a logo or graphic needs a transparent background. WebP can preserve transparency, but it is not always smaller than JPEG: the image and the browser encoder both affect the result. This tool accepts PNG input but does not offer PNG output.
Quality 80 does not mean 80% of the original quality
The quality value is a hint passed to the browser's Canvas encoder. Utilook offers 10–100 and starts at 80. It is not an exact visual-quality percentage or a target file size.
For a web preview or thumbnail, lower the value in small steps and inspect text, edges, and color artifacts. Keep the original if you may edit the image later or need an archival copy.
What Utilook processes
Image Compressor accepts PNG, JPEG, and WebP and uses Canvas to output JPEG or WebP. Input files must be no larger than 10MB, with each side at most 10,000px and no more than 25MP in total.
Encoding and preview happen in your browser; the image file is not uploaded to the server. After a successful result, only a tool-use count request is sent, without image content.