What Is WebP? A Complete Guide to Google's Image Format

WebP is an image format Google developed to make images on web pages smaller. It combines JPG-style lossy photo compression, PNG-style lossless compression and transparency, and GIF-style animation in a single file type. Every current browser displays WebP, yet a WebP you download that will not open in older software is still a common annoyance. This article covers how WebP works, how much it actually saves and what to keep in mind when converting it.

A short history of WebP

Google announced WebP on the Chromium blog on 30 September 2010. The first version offered lossy compression only and was based on the intra-frame coding of the VP8 video codec. The format grew over the following years: Google's WebP FAQ lists lossless compression and transparency as supported from Chrome 23 and animation from Chrome 32. For a long time WebP was defined only by Google's own documentation; in November 2024 it was published by the IETF as RFC 9649, an Informational document written by Google engineers J. Zern, P. Massimino and J. Alakuijala, which also registered the image/webp media type.

How WebP works

The RIFF container

According to RFC 9649, WebP is based on RIFF (Resource Interchange File Format). A file starts with a RIFF header and the WEBP signature, and the image data is stored in chunks. This structure lets one format hold different compression types and extra data side by side.

Lossy WebP (VP8)

Lossy WebP stores the image in a VP8 chunk using VP8 intra-frame coding. Like JPEG it works in blocks, but it predicts each block from neighboring pixels and only codes the difference from that prediction; this predictive coding is the main source of its advantage over JPEG. According to Google's FAQ, lossy WebP works with 8-bit, 4:2:0 chroma subsampling (YUV420), so color is kept at half resolution, as with JPEG's common setting.

Lossless WebP (VP8L)

Lossless mode uses an entirely different bitstream, VP8L. RFC 9649 describes it as combining LZ77, prefix coding and a color cache; together with transforms such as predicting color channels from one another, it compresses better than PNG. It works with 8-bit ARGB data per channel.

Transparency and animation

Lossless WebP includes the alpha channel directly. In lossy WebP, transparency is stored in a separate ALPH chunk, so the photo part can be lossy while edges keep full transparency. Animation uses the ANIM and ANMF chunks, which set each frame's position, duration in milliseconds, blending and disposal method. Unlike GIF, frames are not limited to 256 colors.

Limits

Google's FAQ gives the maximum size of a WebP image as 16383 x 16383 pixels. WebP does not offer progressive or interlaced display in the JPEG or PNG sense. Its color depth is limited to 8 bits, which makes it unsuitable for HDR images; that is where AVIF stands out.

How much smaller is WebP really?

According to Google's own measurements, lossy WebP images are 25-34% smaller than comparable JPEG images at an equivalent SSIM quality index, and lossless WebP images are 26% smaller than PNGs. The same Google page says lossless WebP supports transparency at a cost of just 22% additional bytes. These are averages over Google's test sets; your own images may gain more or less.

Real-world web data tells a similar story: the HTTP Archive Web Almanac 2024 puts the median WebP image on mobile at 1.3 bits per pixel, against 2.0 for JPEG and 3.8 for PNG.

Browser and software support

According to Can I use, browsers with full WebP support account for 97.18% of global usage (October 2026). Full support starts with Chrome 32, Firefox 65, Edge 18 and Safari 16, while Safari 14 and 15 offer partial support. MDN notes that on macOS, Safari needs version 14 or later together with macOS Big Sur (11) or newer to display WebP.

Adoption is growing fast but has not reached JPEG or PNG levels. W3Techs data from October 2026 shows WebP on 22.7% of the websites it monitors. According to the Web Almanac 2024, 12% of images on mobile pages are WebP, a share that grew by about three percentage points between 2022 and 2024.

How to serve WebP on a website

Because every current browser displays WebP, using the image directly as .webp is enough for most sites. If you also need to support very old browsers, the HTML <picture> element lets you list WebP first and a JPG fallback after it. The browser picks the first source it understands:

<picture>
  <source srcset="photo.webp" type="image/webp">
  <img src="photo.jpg" alt="Descriptive alt text" width="1200" height="800">
</picture>

Some servers and content delivery networks return WebP or JPG from the same URL, depending on the Accept header the browser sends. That is convenient, but it is also the main reason people end up with an unexpected WebP file when they choose "Save image as".

Common problems

The WebP I downloaded will not open

Many sites automatically serve images as WebP when the browser supports it. When you choose "Save image as", you end up with a .webp file, and older viewers, some office programs, print services and upload forms that accept only JPG or PNG cannot open it. The most practical fix is to convert the file to JPG or PNG.

An animated WebP stopped moving after conversion

JPG and PNG do not carry animation. When an animated WebP is converted to either format, only one frame remains.

Transparency was lost

When you convert a transparent WebP to JPG, transparent areas are filled with a solid color. Convert to PNG if you need to keep the transparency.

The WebP file is bigger than expected

Converting an already well-compressed JPG to WebP does not always save much, and re-encoding also adds a small quality loss. If lossless WebP was selected, the file can be even larger than the source.

Tips for converting WebP

• To open a WebP anywhere: convert WebP to JPG for photos, or WebP to PNG for transparent images and sharp graphics. For animated WebP files only the first frame is converted.
• To shrink your site's images: our JPG to WebP and PNG to WebP converters use quality 80 by default. For most photos that gives a clear size saving with a loss that is hard to see.
• For logos and screenshots, tick "Lossless WebP". Every pixel is kept exactly and transparency stays, but the file is larger than in lossy mode and can even exceed the source.
• To convert several formats at once, use the image converter; you can add up to 50 files in one go and download the results as a ZIP.
• These conversions run in your browser, so your files never leave your device. EXIF and location data are not written to the output.

Frequently Asked Questions

Is WebP lossy or lossless?

Both. WebP has two separate compression modes, lossy (VP8) and lossless (VP8L). The file extension is the same; which mode was used is stored in the chunk inside the file.

Does WebP open in Safari and on iPhone?

Yes. Current Safari versions fully support WebP. According to Can I use, support was partial in Safari 14 and 15, and full support arrived with Safari 16.

Is WebP better quality than JPG?

A format is not "better quality" on its own; WebP usually gives a better image at the same file size, or a smaller file at the same image quality. In Google's measurements that difference is 25-34% at equivalent quality.

Should I use WebP or AVIF?

AVIF usually produces smaller files for photos and supports HDR, but it is slower to encode and its support on older devices is more recent. WebP encodes quickly and its support goes back further. On websites, a common approach is to offer both through the <picture> element and keep JPG as the fallback.

Do WebP images affect SEO?

WebP itself is not a ranking factor, but smaller images help pages load faster. What matters is serving the image at the right size, with descriptive alt text, and quickly.

Can I print or email a WebP file?

You can, but the recipient's software may not open WebP, and print services and some corporate upload forms often accept only JPG, PNG or PDF. Converting photos to JPG and transparent images to PNG before sharing makes sure the file opens everywhere.

Sources

• RFC 9649: WebP Image Format
• Google for Developers: An image format for the Web
• Google for Developers: WebP Frequently Asked Questions
• Google for Developers: WebP Compression Study
• Chromium Blog: WebP, a new image format for the Web (30 September 2010)
• Can I use: WebP image format
• MDN: Image file type and format guide
• W3Techs: Usage statistics of image file formats for websites
• HTTP Archive Web Almanac 2024: Media