Choosing the wrong image format for your website can silently cost you page speed, Core Web Vitals scores, and bandwidth. Choosing the right one is free — it just requires knowing which format does what.
Here is a practical breakdown of every format you will encounter, when to use each one, and how much file size you can save by switching.
The formats at a glance
| Format | Type | Transparency | Typical size vs JPG | Browser support |
|---|---|---|---|---|
| AVIF | Lossy | Yes | −50% | Chrome 85+, Firefox 93+, Safari 16+ |
| WebP | Lossy/Lossless | Yes | −25–35% | All modern browsers |
| JPG | Lossy | No | baseline | Universal |
| PNG | Lossless | Yes | +20–60% | Universal |
| GIF | Lossless (256 colors) | 1-bit | +200–500% | Universal |
| BMP | Lossless (uncompressed) | No | +500%+ | Universal |
JPG — the reliable default
JPEG (Joint Photographic Experts Group) has been the standard for photographs since the 1990s. It uses lossy compression to achieve good file sizes while maintaining acceptable visual quality for photos.
Use JPG when: You need universal compatibility, you are sharing images with people on old devices or software, or you are uploading to platforms that re-compress images anyway (social media).
Avoid JPG for: Logos, screenshots, text, diagrams, or anything with sharp edges and flat colors — JPEG compression introduces visible artifacts (blurring, "ringing") on hard edges.
PNG — lossless and transparent
PNG (Portable Network Graphics) stores images losslessly — every pixel is preserved exactly. It also supports full alpha-channel transparency. The tradeoff is larger file sizes, especially for photos.
Use PNG when: You have a logo, icon, or screenshot that needs sharp edges. You need transparency (e.g., overlaying an image on a colored background). The image has text or fine detail that must be pixel-perfect.
Avoid PNG for: Photographs. A photo saved as PNG can be 3–5× larger than the same image as a JPG or WebP with no perceptible quality difference.
WebP — the modern default
Developed by Google and released in 2010, WebP supports both lossy and lossless compression, full transparency, and animation. It is supported by all major browsers released since 2019.
A WebP image is typically 25–35% smaller than an equivalent JPEG and 26% smallerthan an equivalent PNG (according to Google's benchmarks).
Use WebP when: You are building a modern website and want the best balance of compression and compatibility. This is the right default choice for 95% of web images today.
AVIF — the best compression available
AVIF (AV1 Image File Format) is based on the AV1 video codec and offers significantly better compression than WebP — typically 40–50% smaller than JPEG at equivalent quality. It supports HDR, wide color gamut, and 12-bit color depth.
Use AVIF when: Your audience uses modern browsers (Chrome, Firefox, Safari 16+). You want the absolute smallest file sizes. This is the format of the future.
Caveats: Encoding is slower than WebP (matters for dynamically generated images). Not supported in Internet Explorer or Safari before version 16. If you must support older browsers, serve WebP as a fallback with <picture> element source sets.
Simple decision guide
Convert between formats in your browser
The 365tools Image Converter supports PNG, JPG, WebP, AVIF, GIF, and BMP. Batch conversion, quality control, ZIP download — 100% client-side, no uploads.
Open Image Converter →Frequently asked questions
Should I convert all my images to WebP?
For web use, yes — WebP is supported by all modern browsers and typically saves 25–35% file size over JPG with equal quality. The main exception is when you need universal compatibility including very old browsers (IE11), in which case JPG/PNG remain safer.
Is AVIF better than WebP?
AVIF generally achieves 20–30% better compression than WebP at the same quality, making it the best format for file size. However, AVIF is not supported in older browsers (pre-2020) and encoding is slower. For maximum compatibility, use WebP; for maximum compression on modern-only audiences, use AVIF.
When should I use PNG instead of WebP?
Use PNG when you need lossless quality — for screenshots, diagrams, logos with sharp edges, or images with text. WebP can also be lossless, but PNG has broader legacy support. For lossy photos, WebP is almost always better than PNG.
Does converting JPG to WebP reduce quality?
Converting from JPG to WebP at a high quality setting (85+) produces results visually indistinguishable from the original. However, every re-encode of a lossy format introduces some loss. To minimise this, start from the highest-quality source you have.
What about GIF vs WebP for animations?
WebP supports animation and is dramatically smaller than GIF — typically 64% smaller than animated GIFs. If you need animation, use animated WebP or consider a short MP4 video, which is even smaller and more compatible.