What resizing an image actually changes

The Image Resizer changes the pixel dimensions of a picture with precision. Give it an exact width, an exact height, or both, or scale the whole image by a percentage between 1 and 500. Resampling uses the Lanczos filter, the same method photo editors use for their highest-quality setting, so downscaled images stay crisp instead of turning mushy. Output can be as large as 10000 pixels per side, and transparent PNGs keep their transparency.

When the resize finishes you get a hosted copy with a shareable URL immediately, plus a download button. Percentage scaling accepts anything from 1% to 500%, and any single side is capped at 10,000 pixels.

Pixels or percentage

Use pixel mode when a platform or a person gives you a number: a 1200px-wide blog image, a 400px avatar, an 800px forum limit. Enter one dimension and the other is calculated for you, so a 4000 by 3000 photo set to 1200 wide comes out at exactly 1200 by 900. Use percentage mode when you care about proportion rather than a target: half size for an email attachment, 25 percent for a quick preview, 150 percent for a modest enlargement. Percentage mode is also the fastest way to shrink a whole batch of photos consistently, since the same factor applies sensibly to portrait and landscape shots alike.

The keep-aspect toggle

With keep-aspect on, the image scales uniformly. Enter both a width and a height and the picture is fitted inside that box without stretching, which is what you want almost every time. Turn the toggle off only when you deliberately need the image forced to exact non-proportional dimensions, such as filling a fixed slot in a template, and accept that subjects will look stretched or squashed. If what you actually want is a different shape without distortion, trim the image with the image cropper instead of disabling aspect lock.

When to resize an image

  • Meeting upload limits on forums, marketplaces, and application forms that reject anything over a fixed dimension.
  • Cutting oversized camera photos down to sensible web dimensions before publishing, since no visitor needs a 6000px original.
  • Producing consistent thumbnails or gallery images at one fixed width so a grid lines up cleanly.
  • Shrinking screenshots so they read at a glance in documentation and bug reports.
  • Matching each network's preferred dimensions, listed in the image size cheat sheet for social platforms.

Tips for resizing without softening

  • Downscaling is essentially lossless to the eye; enlarging past the original softens detail. To grow an image convincingly, use the AI image upscaler rather than percentage mode.
  • Resize first, then compress. A 1200px image compressed well beats a 4000px image compressed hard, at a fraction of the weight. The guide to reducing image file size walks through the full order of operations.
  • Keep a full-resolution original. You can always make a big image smaller, but not the reverse without AI help.