The selected image is decoded and rendered to an HTML canvas in the browser. Resizing uses high-quality browser interpolation, and JPEG or WebP quality controls the encoder setting used for the downloaded file.
JPEG cannot preserve transparency, so transparent pixels receive a white background. File size depends on image detail, dimensions, format, and encoder implementation.
Questions
Image Compressor FAQ
What does the quality slider change?
For JPEG and WebP it adjusts lossy encoding quality. Lower settings usually create smaller files with more visible artifacts.
Why might a PNG not become smaller?
PNG is lossless and does not use the same quality setting. Converting a photographic PNG to WebP or JPEG can reduce size substantially.
