WebP, JPEG or PNG? An honest guide to smaller website images.

Three formats, three different jobs

JPEG is familiar and practical for photographs. It uses lossy compression, which is why you can make a photographic image smaller by discarding detail the encoder considers less noticeable. It does not support transparent backgrounds.

PNG is lossless and supports transparency. It can be a good choice for graphics, icons or screenshots where exact edges matter, but photo-sized PNGs can become enormous. WebP supports transparency and can be lossy or lossless; its lossy mode is worth trying when you want a smaller modern web image.

File size has two major levers

First, shrink unnecessary pixel dimensions. If you display an image at 900 pixels wide but upload a 5000-pixel source, you're making users download detail the layout doesn't need. Second, choose encoding settings that preserve enough visible quality while using fewer bytes.

The RezSat Image Compressor offers both choices. You can export a file at its existing dimensions or cap its maximum width or height. Then choose WebP, JPEG or PNG and, for the lossy formats, test a quality setting. The result displays the actual bytes saved or added.

What quality percentage actually means

A quality setting of 80 does not mean the output retains exactly 80 percent of all visual information. It is an instruction to the browser's encoder, and different formats and browser implementations may behave differently. The useful comparison is visual: does the result still show the detail your visitor needs?

Start around the default and inspect fine textures, lettering and faces. If small text in the image becomes difficult to read, raise the quality or use a more suitable format. The number on the slider is not an objective quality score.

Why your compressed image could get bigger

An already optimized JPEG might become larger after being re-encoded. A PNG produced by a browser can be heavier than the original file, especially if that original used a limited color palette. The file size report isn't wrong; the export choice simply didn't save space.

Try a different format or pixel size, and keep the original for comparison. Compression is successful when the result looks appropriate and has a worthwhile size—not because a button happened to say 'Compress'.

Privacy and the hidden cost of uploads

For an everyday picture, sending it to an outside converter may feel harmless. For internal product mockups, unpublished artwork or customer images, it's sensible to know whether the service uploads the file, stores it or processes it locally.

RezSat's current image resizer, compressor and converter operate in the browser. The image data is not intentionally transmitted to RezSat. Your device still needs enough memory to decode and re-encode the picture, so very large files may not work on older phones.

The best final check is an actual page

After replacing an image on a website, test it where it is used. A small thumbnail can look fine in isolation and ugly stretched across a hero. Check mobile and desktop, cropping, the image's displayed dimensions and the network transfer. It's the page experience that counts, not the trophy for the smallest file.