Image guide · Updated October 7, 2026
Resize or compress: which change do you need?
Pixel dimensions describe the image grid. File size describes the bytes used to store it. They solve different problems.
Start with the practical decision
Choose the grid before chasing the bytes
The same photo has 2976 × 3968 pixels at original size and 1488 × 1984 at 50%. The resized, target-200-KB result is 181,937 bytes; it is not a same-dimension quality comparison because both settings changed. At 10%, a separate 20 KB case becomes only 298 × 397.
- Find the destination’s display size or stated minimum dimensions.
- Keep Original dimensions for printing or a minimum-grid requirement; fit or scale only when fewer pixels are appropriate.
- Compare the resized download at its intended display size. Keep the original for larger uses.
Compression keeps the grid unless you ask otherwise
With Original dimensions selected, a 1200 × 800 input keeps that pixel grid. A lossy JPEG, WebP, or AVIF output can use fewer bytes by representing detail less precisely. Inspect edges, skin, and gradients in Compare. PNG optimization instead tries to represent the same prepared pixels more efficiently.
Resizing removes pixels
Changing a 1200 × 800 image to 50% produces 600 × 400: half the width and height, but one quarter of the pixels. This does not promise a fourfold reduction in bytes; format, detail, and metadata also matter. Once detail has been removed, enlarging the smaller file cannot restore it.
Fit within a box without stretching
Choose Fit within dimensions and keep the aspect-ratio lock on. A landscape image fits inside both maxima; it does not necessarily fill the box. For example, 1200 × 800 fitted inside 500 × 500 becomes 500 × 333 after rounding. The app does not crop it into a square or enlarge a smaller source to fill the box.
A practical order for web images
First choose dimensions that suit where the image will be displayed. Then choose the destination’s supported format. Finally reduce quality or set a file-size limit and inspect the result. For a high-density display, a 400 CSS-pixel placement may benefit from an 800-pixel source. That is a display choice, not a rule every upload needs.
When preserving dimensions matters
An ID form, print workflow, or marketplace can require minimum dimensions even when it also imposes a byte limit. Start with compression alone in those cases. If the target fails, do not resize below the receiving service’s stated minimum. Our examples compare identical source pixels with explicit scale changes so you can see what each control did.
Try it with a reproducible example
Open the source files, measured outputs, and settings. Use the same source for each comparison and inspect the actual result.