Choosing the wrong image format costs you page speed, user experience, and bandwidth. Here's a practical guide to the four major formats and when each makes sense.
JPEG (JPG) — Still the universal standard
Best for: Photographs, complex images with many colors.
JPEG uses lossy compression that works well for natural scenes. It's supported everywhere. The downsides: no transparency, no animation, and visible artefacts at very low quality settings.
When to use it: Background photos, product images on e-commerce, hero banners. Basically any photograph where file size matters more than perfection.
PNG — For precision
Best for: Screenshots, logos, images with text, graphics with sharp edges.
PNG offers lossless compression with full transparency support. The tradeoff is file size — PNGs are typically 2-5x larger than JPEG for photographs.
When to use it: UI elements, logos, screenshots, infographics. Anything with text or sharp edges where JPEG artefacts would be noticeable.
WebP — The modern default
Best for: Replacing both JPEG and PNG in most cases.
WebP supports both lossy and lossless compression, plus transparency and animation. Lossy WebP is 25-35% smaller than JPEG at the same quality. Lossless WebP is 25-30% smaller than PNG.
When to use it: Everything new. Browser support is 97%+. Convert existing JPEGs and PNGs to WebP for immediate bandwidth savings.
AVIF — The next generation
Best for: Maximum compression, HDR images, wide color gamut.
AVIF is 50-60% smaller than JPEG at the same quality. It supports HDR, 10/12-bit color, and transparency. The tradeoff is slower encoding (2-3x slower than WebP).
When to use it: Hero images, large photos, and when every kilobyte matters. Browser support is at 91% and growing.
Quick decision guide
| Use Case | Best Format | Why |
|---|---|---|
| Photo on a website | WebP or AVIF | 25-60% smaller than JPEG |
| Logo with transparency | PNG or WebP | Needs alpha channel |
| Screenshot | Lossless WebP | Smaller than PNG, same quality |
| Email attachment | JPEG | Universal compatibility |
| E-commerce product photo | WebP | Best size-quality balance |
| Social media image | JPEG or PNG | Platform re-encodes anyway |
| GIF replacement | WebP animated | Smaller than GIF, better quality |
The one tool you need
ToolBox Image lets you convert between all four formats instantly in your browser with no uploads. It also has target-size compression so you can set an exact file size limit. Free, no sign-up.
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