Rasp

File format

WebP

Smaller than JPG, transparent like PNG, supported by every current browser — and still refused by a surprising amount of desktop software.

What is a WebP file?

WebP is an image format Google published in 2010 to make web pages lighter. It compresses better than JPG, supports transparency like PNG, and does both in one format. Every current browser displays it. Outside the browser, support is patchy — which is why downloaded WebP files often refuse to open.

The facts

Full nameWebP
File extensions.webp
MIME typeimage/webp
Introduced2010
Created byGoogle
CompressionLossy and lossless
TransparencySupported
SpecificationWebP — an image format for the web

Why Google made a new image format

By 2010, images were the bulk of what a web page downloaded, and the formats doing the work were from 1992 and 1996. WebP was Google’s attempt to replace both at once.

It borrows its compression from VP8, a video codec, applying the prediction techniques video coding had developed to still images. The same idea appeared later, more aggressively, in AVIF.

Crucially it also merged two roles. Before WebP you chose between JPG’s compression and PNG’s transparency. WebP does both, including the previously impossible combination of lossy compression with an alpha channel.

What the saving actually is

Measured on the fixed test image used throughout this site, from the same source:

  • 375 KB as JPG
  • 247 KB as WebP — about 40% smaller
  • 109 KB as AVIF

Your own images will differ. Photographs with heavy fine texture narrow the gap; images with large areas of flat colour widen it.

The compatibility asymmetry

This is the thing to understand about WebP, and it explains almost every problem people have with it.

In browsers, WebP is universal. Chrome, Edge, Firefox, Opera and Safari all render it, and have since Safari joined in 2020.

Outside browsers, it is patchy. Many desktop photo viewers, plenty of older editors, most print workflows and a long tail of upload forms still reject it.

So a format designed to be served by websites is served by websites — and the moment you save one of those images to your disk, you are outside the environment it was designed for. That mismatch is why “how do I open a WebP file” is such a common question.

Practical rules

  • Publishing to a site you control — use WebP. The bandwidth saving is real and every visitor’s browser can read it.
  • Sending a file to a person — convert to JPG. You cannot predict their software.
  • Editing — convert to PNG if your editor refuses WebP, accepting that it will be much larger.
  • Squeezing further — convert to AVIF, if your audience is current.

Converting into WebP

From JPG, PNG, HEIC or AVIF.

If you are converting iPhone photos for a website, go directly from HEIC rather than via JPG — two lossy steps discard more than one.

Convert WEBP files

From WEBP

To WEBP

Questions

Why did my download save as a WebP?
Because the site served one. WebP is smaller than JPG, so sites use it to save bandwidth, and saving an image from a modern web page gives you whatever the browser was sent — often a WebP even when the original upload was a JPG.
How do I open a WebP file?
Any current web browser will display one: drag the file into a browser tab. For editing, either use software with WebP support or convert it to JPG or PNG first.
Is WebP better than JPG?
On file size, clearly. On our fixed test image, converting the same source produced a 375 KB JPG and a 247 KB WebP — around 40% smaller. WebP also supports transparency, which JPG cannot. JPG wins only on universality, and that is not a small thing.
Does WebP support transparency?
Yes, including partial transparency, in both its lossy and lossless modes. Lossy-with-alpha is a genuinely useful combination that neither JPG nor PNG offers.
Is WebP lossy or lossless?
Both, depending on how it is encoded. Lossy WebP is the common case and where the size savings come from. Lossless WebP exists and typically beats PNG, but is much less widely used.
Do all browsers support WebP?
Every current one, including Safari since 2020. On the web it is effectively universal now. The gaps are in desktop applications, print workflows and upload forms.
Should I use WebP or AVIF?
AVIF compresses harder — 109 KB against WebP's 247 KB on our test image. WebP encodes far faster and is accepted by slightly more software. Serving both from a picture element avoids choosing.
Can I email a WebP?
You can, but do not. Whether it opens depends entirely on the recipient's software, and you cannot know that. Convert to JPG for anything you send to a person.

Sources