A short history
Google announced WebP in September 2010, shortly after acquiring On2 Technologies and open-sourcing its VP8 video codec. The idea was simple: a single video frame compressed with VP8 was already smaller than a JPEG, so why not turn it into an image format? Lossless compression and alpha transparency were added in 2011–2012, and animation followed. WebP is released under a BSD licence with a royalty-free patent grant, which is why it has been adopted so widely.
How WebP compression works
Lossy WebP borrows the intra-frame coding tools of VP8. The image is split into macroblocks; each block is predicted from already-encoded neighbours using one of several modes, and only the residual difference is transformed (DCT/WHT), quantised and entropy-coded with an adaptive arithmetic coder. A loop filter then smooths block boundaries. JPEG, by contrast, has no prediction and uses a simpler Huffman coder, which is why WebP needs 25–35% fewer bytes for the same quality.
Lossless WebP is a completely different algorithm that uses spatial prediction, colour transforms, a local colour cache and LZ77 with Huffman coding. It is about 26% smaller than PNG on average and, unlike PNG, can be combined with a lossy colour channel plus lossless alpha.
What WebP supports
- Lossy and lossless compression in the same format.
- Alpha transparency (8-bit) in both modes.
- Animation, as a replacement for GIF.
- Metadata: EXIF, XMP and ICC colour profiles.
- Dimensions up to 16,383 × 16,383 pixels.
How much smaller is WebP?
| Compared with | Typical WebP saving |
|---|---|
| JPEG (lossy, same SSIM) | 25–35% smaller |
| PNG (lossless) | ~26% smaller |
| PNG (converted to lossy WebP) | 60–85% smaller |
| GIF (animated) | 50–70% smaller |
Browser support
WebP is supported by every modern browser: Chrome and Opera since 2010, Firefox and Edge since 2019, Safari since macOS 11 Big Sur and iOS 14 (2020). Global coverage exceeds 97% of users. Only Internet Explorer and some legacy email clients lack support, and those are easily handled with a fallback via the <picture> element.
Pros and cons
Advantages
- Much smaller files, therefore faster pages and lower bandwidth bills.
- One format for photos, graphics, transparency and animation.
- Fast encoding: browsers can convert images in milliseconds, which is how this site works.
- Universal support in browsers, CMSs, CDNs and social platforms.
Limitations
- 8-bit colour only (no 10/12-bit HDR like AVIF).
- No progressive rendering mode.
- Maximum dimension of 16,383 px per side.
- Slightly less efficient than AVIF at very low bitrates.
How to convert images to WebP
You do not need any software. Fast WebP Converter runs entirely in your browser: drop a PNG, JPG, GIF, BMP, AVIF or SVG, choose a quality and a maximum width, and download the WebP. Nothing is uploaded. For bulk conversions, PRO handles up to 100 images at a time and packages them as a ZIP.