What the result must satisfy
A successful result has an encoded file size no greater than the selected limit in bytes. The tool does not pad a smaller file to make its size look exact. A result below the limit can be correct even when it is several kilobytes smaller than your target. Always check the success message and exact byte count rather than only a rounded size.
Decode, resize, then search
JPG, PNG and WebP inputs use the browser’s image decoder. HEIC/HEIF uses an additional decoder loaded when needed. The image is drawn onto a canvas and encoded as the selected output format. Large images can be resized before the quality search: the implementation applies a 24-megapixel ceiling, a target-dependent pixel budget, and any dimension cap you select. The automatic setting therefore does not guarantee that original dimensions will remain unchanged.
For JPG and WebP, the tool probes encoder quality settings from approximately 0.08 to 0.95. It keeps a fitting result and narrows the search, with additional refinement. If the image still cannot fit, it reduces dimensions and tries again. This is the best result found by a bounded search, not proof of the mathematically optimal encoding. Different browsers can produce different bytes from the same input.
What “quality 68%” means
That number describes an encoder setting. It is not a measurement showing that 68% of visual detail survived. Inspect edges, small lettering and smooth backgrounds at a sensible viewing size. Read dimensions alongside quality: a sharp thumbnail and a larger low-quality image solve different problems.
PNG and transparency
PNG output has no JPEG-style quality slider. To reduce its size, the tool changes dimensions. PNG and WebP can preserve transparency; JPG cannot, so transparent areas are placed on white for JPG output. Re-encoding is not an archive of the original file. Keep your original separately.
When a target cannot be met
The tool has a limited number of resize attempts. A “Could not fit” result must not be treated as success. Use a larger allowed budget, prepare a tighter crop in an image editor, or choose another permitted format. The tool does not crop a face or enforce minimum photo dimensions.
Try the compressor, then compare measured quality examples and the upload troubleshooting checklist.
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