Image compression without the guesswork
Understand how compression, pixel dimensions and file formats affect KB and MB limits and visible quality.
Reviewed September 20, 2026
Compression reduces the number of bytes an image uses. Resizing is a different step. A large photo can be compressed without changing its dimensions, and a resized photo can still be a big file. Keeping the two ideas apart makes most upload problems much easier to solve.
Open the image compressorStart with the requirement you actually have
A limit such as 500KB is about file size. A requirement such as 1080 × 1080 is about dimensions, the number of pixels across and down.
If a site asks for both, resize or crop first and compress second. That way no bytes are spent on pixels that will never be shown.
Why photos and graphics compress differently
- Photos have smooth tones and irregular detail. Lossy formats such as JPG and WebP handle them well.
- Logos, screenshots and diagrams have flat color, sharp edges and text. PNG keeps them crisp, but the files can be larger.
What happens when you push the target too low
Heavy compression can cause blocky patches, halos around edges, smeared texture and blurry text.
Aim for the smallest file that still looks acceptable where it will be used, not the smallest number possible. Judge the result at the size people will actually see it. Zooming far in exaggerates flaws, and tiny thumbnails can hide real damage.
100KB, 200KB, 500KB or 1MB?
Small targets work for strict forms and thumbnails. Larger targets leave room for detailed photos.
No file size guarantees a particular quality. Two images with the same dimensions can hold very different amounts of detail. A 4000 × 3000 photo of a busy street needs far more bytes than a 1200 × 900 photo of a plain wall.
Keep the original
Treat the compressed file as a delivery copy and keep the original. You can then make a new copy later for print, another platform or a looser limit.