Choose the best image file format for the web

When adding an image to a web page, people often overlook the file format. But the format can directly affect image quality, page speed, and even whether the image renders at all. Not every browser supports every image type.

To choose the best image file format, focus on three practical requirements:

- Good visual quality -
- Fast page loading (small file size) -
- Support across the widest range of browsers and devices -

For most websites, the two most common and widely supported formats are JPEG (.jpg) and PNG (.png).

Which one should you use? It depends on the content of the image. If you are working with a photo that contains many colors and smooth gradients (portraits, travel photos, events), JPEG is usually the best choice. It keeps a good balance between quality and file size.

This photo in JPEG format is 148 KB (the same image as PNG would be 1.52 MB - more than 10x larger):

If the image is a document page, a UI screenshot, a diagram, or anything with sharp edges and a limited number of colors, PNG is often a better option. It preserves crisp lines, supports transparency, and can be smaller than JPEG for this type of content.

This PNG image is 41 KB (as JPEG it would be almost twice as large and would lose transparency):

Simple rule of thumb: photos and portraits - JPEG; diagrams, screenshots, documents, logos - PNG.

Here is a portrait photo album example (JPEG), hosted on Photo-Pick: