Choosing the right image format helps pages load faster without making images look poor. The best format depends on the image type and browser support you need.
JPEG
JPEG is still useful for photographs. It is widely supported and can be small when compressed carefully, but repeated editing and saving can reduce quality.
PNG
PNG is best for sharp graphics, screenshots, and images needing transparency. It is often too large for full photographic images.
WebP
WebP is a good default for many website images. It supports lossy and lossless compression and can handle transparency.
AVIF
AVIF can produce very small files with good quality, but encoding can be slower and workflows vary. Use fallbacks if your audience includes older browsers.
Do Not Forget Dimensions
Format helps, but oversized dimensions still hurt. Resize images to suit the layout and use responsive image sizes where your CMS supports them.
The best workflow is simple: upload sensible dimensions, compress images, and serve modern formats with fallbacks where needed.
Choose by Image Type
Use JPEG or WebP for photographs where small colour changes are acceptable. PNG suits screenshots, diagrams and transparency when crisp edges matter, although WebP can often provide transparency at lower size. AVIF can compress photographs very well but may take longer to encode and should be tested for browser and tooling support.
Dimensions Matter More Than the Label
A 4,000-pixel image remains wasteful after format conversion if it is displayed at 600 pixels. Generate several widths and use srcset and sizes so the browser selects an appropriate file. Declare width and height to reserve layout space and prevent content shifting.
Measure Visual Quality
Compare files at the size customers will see, especially text, gradients, logos and faces. Avoid repeated lossy conversions from already compressed originals. Keep a high-quality source outside the public website, automate derivatives, lazy-load below-the-fold images and give the main page image appropriate priority.
