How to reduce an image’s file size

Open Image Compressor

Application forms often ask for a photo under 100 KB or a scan under 500 KB, while a photo from a phone can be 3 MB or more. You can usually get under the limit and still have a clear picture.

What makes an image file big

Three things decide the size:

Dimensions: how many pixels wide and tall the image is. A phone photo may be 4,000 pixels wide, far more than a form needs.
Quality: how much detail the file keeps. Lowering it a little saves a lot, and is hard to see.
Format: JPG and WebP suit photos. PNG keeps every pixel, so a photo saved as PNG is much larger.

Get an image under a size limit

Open Image Compressor.
Choose Target file size, type the number and pick KB or MB.
Add your images and press the button to compress them.
Download the result and check it looks right.

Each image is saved at the highest quality that stays under your limit. Forms don’t agree on whether a kilobyte is 1,000 or 1,024 bytes, so 25 KB here means at most 25,000 bytes, which passes either way.

If the image comes out smaller than you expected

When a limit is tight, lowering the quality further would make the picture blocky, so the tool scales it down instead and tells you the new size. If a form asks for exact dimensions as well as a file size, such as 413 by 531 pixels, set those first in Image Resizer, then compress the result.

Which format should you choose?

Leave it on Best for each image unless the form names a format. If it asks for JPG, choose JPG: it’s accepted everywhere. WebP is smaller and keeps see-through areas, and every current browser shows it, but some forms still don’t accept it.

To keep a logo or screenshot as a PNG, choose PNG (fewer colours). The image is reduced to 256 colours, which usually makes it several times smaller and keeps its transparency. Photos with smooth skies or shadows can show faint bands this way, so use it for flat graphics.

Scans and photos of documents

Before you compress, crop away the desk or background around the page with Crop Image. There’s less to store, and the page itself keeps more quality at the same file size. Then zoom in on the result and make sure small print is still readable.

A bonus: location details are removed

Phone photos can carry hidden details such as where they were taken and which camera took them. Compressed files don’t include these details. If an image was already under your limit, the original is kept unchanged, and so are its details. To see what a photo holds, use Image Metadata Viewer.