PNG is lossless, so there is no quality dial like JPG has. Screenshots and logos with flat colour compress very well. Photos saved as PNG are large, and the honest answer for those is to switch format.
Choose PNG as the output. PNG output is always lossless: every pixel stays exactly the same and transparency is kept, and the quality slider does not change PNG output. To make a PNG smaller, use the resize option, or set a target size and let the tool reduce the pixel size in steps.
If a PNG is a photograph and does not need transparency, converting to JPG or WebP usually gives a far smaller file. If it needs transparency, WebP supports it and is usually smaller than PNG. See how to convert PNG to WebP.
Animated PNGs are not supported and only the first frame is read. Metadata is removed. Check the result before replacing an original, especially for logos you need exact.
The free Image Compressor handles 25 images at a time, with no signup and no upload.
Open the free Image Compressor