How to Reduce Image Size Without Losing Quality
Four simple levers that shrink an image file: dimensions, compression quality, format and cropping, and the order to use them in.
An image file is large for a few simple reasons: it has many pixels, it stores a lot of detail for each one, and it may be saved in a format that does not compress well. Once you know which of these is the problem, shrinking the file is easy and you can keep it looking good.
The four levers
- Dimensions. A photo from a phone camera has far more pixels than any form or web page can show. Reducing the width and height is the biggest saving and costs almost nothing in visible quality on a normal screen. Use the resize tool.
- Compression quality. JPG files can be saved at different quality levels. A small drop in quality can cut the file size a lot while looking almost the same. The compress tool finds the highest quality that fits your limit.
- Format. JPG is usually the smallest choice for photos. PNG is better for logos and text but is much larger for photos. See JPG vs PNG.
- Cropping. Fewer pixels means a smaller file. Cut away empty space around the subject before anything else.
A good order to work in
- Start from the original photo, never from a copy that was already compressed.
- Crop to the part you really need.
- Resize to the dimensions you actually need.
- Compress to the target size.
Why quality drops
JPG compression throws away fine detail that the eye notices least. Every time you save a JPG again, a little more is thrown away, so repeated saving makes images look worse. That is why you should always go back to the original.
Plain backgrounds and smooth areas compress very well. Busy textures, such as leaves or fabric, take more space for the same quality, so they hit a size limit sooner.
Try it
If you need a specific size, pick it here: 50 KB, 100 KB, 200 KB or 500 KB.