What Is WebP? The Modern Image Format Explained and Why It Matters

WebP is an image format developed by Google with lossy and lossless coding, transparency, and animation. Google’s published corpus reported smaller files than JPEG or PNG under specified comparison methods, but that is a benchmark result rather than a promise for every conversion. Current major browsers support WebP; other software and older clients still need checking.

How WebP Came to Exist

Google announced WebP on September 30, 2010, positioning it as a modern replacement for JPEG on the web. The format was born from a video codec: Google had acquired a company called On2 Technologies, which developed the VP8 video format. Google's engineers realized that VP8's compression techniques — designed to shrink video frames — could also produce remarkably small still images.

The early years were slow. Google shipped WebP support in Chrome almost immediately, but other browser vendors were skeptical. Mozilla publicly questioned whether the quality gains justified adopting yet another format. Apple ignored it entirely.

The turning point came gradually:

• 2012 — Chrome’s WebP implementation expanded to lossless and alpha capabilities
• 2014 — WebP support continued spreading through Chromium-based and Android browser paths
• 2019 — Firefox 65 added WebP support
• 2020 — Safari support arrived with the iOS 14 and macOS Big Sur generation
• Today — current major browsers support WebP, while old releases and non-browser consumers still require checking

Safari support removed a major compatibility gap, but “browser support” is not the whole delivery chain. Embedded webviews, email clients, crawlers, editors, native apps, and long-lived devices can follow different timelines.

How WebP Compression Works

WebP offers two compression modes, each suited to different types of images:

Lossy Mode (for Photos)

Lossy WebP uses predictive coding based on VP8 — the encoder analyzes each block of pixels, predicts what it should look like based on surrounding blocks, and then stores only the difference. This technique is particularly effective for photographs with smooth gradients and organic textures.

Google’s comparative study reported lossy WebP files 25–34% smaller than comparable JPEG files at equivalent SSIM for its test corpus. That result is useful context, not a per-file expectation: source history, encoder versions, settings, metadata, and the chosen quality metric change the outcome.

Lossless Mode (for Graphics)

Lossless WebP uses techniques including spatial prediction, color transforms, palette coding, and entropy coding. Decoding can restore the encoded pixel values, while metadata, profiles, and handling of fully transparent RGB values remain separate workflow concerns.

Google’s published corpus reported lossless WebP files about 26% smaller than PNG on average. An individual file can shrink less or even grow. Lossless mode restores pixel values, while metadata and fully transparent RGB handling can still depend on encoder settings.

WebP vs. JPEG vs. PNG: Side-by-Side

WebP combines capabilities that otherwise span JPEG, PNG, and animated formats, but it is not guaranteed to be smaller or more compatible in every workflow. Google documents a maximum WebP canvas dimension of 16,383 × 16,383 pixels for the general bitstream, which is a real constraint for very large images.

Why Modern Websites Use WebP

Image transfer and decoding can affect user experience and Core Web Vitals when images are the bottleneck. A smaller WebP candidate can reduce transfer, but conversion alone does not guarantee a smaller file, faster LCP, or a ranking change. Measure the page and preserve a suitable fallback.

The HTTP Archive can show current format use across its corpus. Many content systems, image libraries, and CDNs can accept or generate WebP, but capabilities and plan terms change. Confirm whether your specific pipeline preserves animation, alpha, profiles, metadata, and cache variation correctly.

For individual site owners and developers, the conversion is straightforward. You can convert JPG to WebP or convert PNG to WebP directly in your browser using Vizua, without installing software or sending selected image contents to Vizua for conversion.

When Not to Use WebP

WebP is excellent for web delivery, but it is not the right choice for every scenario:

• Archival storage — use the format, metadata policy, fixity checks, and redundancy defined by your archive rather than assuming a web-delivery format is archival.
• Print workflows — ask the printer for accepted formats, profiles, resolution, and proofing requirements before delivery.
• Email attachments — JPEG or PNG may be more interoperable with older clients and recipient software; test the actual destination.
• Images above 16,383 pixels in either dimension — the general WebP bitstream limit is 16,383 x 16,383. Use a suitable larger-canvas format, tiling strategy, or pyramid workflow instead.

WebP is a strong web-delivery candidate, not an automatic replacement for the master. Keep a suitable source and generate delivery variants for the web, print, email, or archive according to each destination’s requirements.

Need to go the other direction? Vizua also handles WebP to JPG conversion and WebP compression for files that are already in the format.

WebP and the Future: AVIF Enters the Picture

AVIF is a newer format based on AV1 image coding and can outperform WebP in some benchmark and production comparisons. The margin depends on content, encoders, settings, and quality measurement. Support has expanded in current browsers, while older clients and non-browser software still vary.

AVIF does not make WebP obsolete. Encoding cost, decode behavior, features, tooling, and compatibility differ. A <picture> stack can offer AVIF, WebP, and JPEG candidates, but correct source order does not guarantee the smallest file unless each candidate was generated and tested well.

WebP is often a practical starting candidate because current browser support and tooling are broad. Test AVIF when your build pipeline, quality review, fallbacks, and audience support it.

Frequently Asked Questions