How to Use This Tool
Resizing sounds like the simplest image operation there is, and browsers do it badly enough that most online resizers produce visibly worse results than they need to. This one handles the two things that matter: keeping the aspect ratio honest, and downscaling in stages so large reductions stay sharp.
Three ways to specify the size
Exact pixels with the lock closed means typing a width and having the height follow automatically. Open the lock and you can set both independently — the image will be stretched, which is almost never what you want but is occasionally exactly what you want.
Percentage is the fastest option when you just need "smaller". Half size is a quarter of the pixels and usually about a quarter of the file, which is why 50% is such a common answer.
Fit inside takes a single number for the longest side and works for portrait and landscape together. This is the right mode for batch work: a folder of mixed orientations all constrained to 1600px without you sorting them first.
The stepped downscale, and why it matters
Browsers use a fast bilinear filter that samples only a few neighbouring pixels. Going from 4000px to 400px in one call means most of the source image is never looked at, which produces aliasing — sparkly, broken-looking edges on anything with fine detail. This tool halves repeatedly until it is within a factor of two of the target, then does the final step. Every source pixel ends up contributing, and the result is visibly smoother on text, hair, brickwork and fabric.
Enlarging
Never enlarge beyond the original is ticked by default, and you should usually leave it that way. Scaling up cannot add detail that was never captured; it interpolates, which produces a softer, blurrier version of the same image at a larger file size. If a print shop asks for more pixels than you have, the honest answer is that the source is too small, not that a resizer can fix it.
Format and quality
Keep original preserves PNG transparency and JPEG compatibility. Switching to JPEG flattens any transparency onto white. WebP is the best choice if the destination accepts it — same visual quality, much smaller. Quality 90 is a sensible default after resizing, because a downscaled image has already lost the fine detail that low quality settings damage most.
