.WEBP

WebP image

Introduction

WebP is an image format released by Google in 2010 to make web pages lighter. Its lossy mode is based on the intra-frame coding of the VP8 video codec; a separate lossless mode followed. WebP supports alpha transparency in both modes and animation, so it can stand in for JPEG, PNG and GIF.

All current web browsers display WebP. The format was published by the IETF as RFC 9649 in 2024.

Software

Structure

A WebP file is a RIFF container: the bytes RIFF, a 4-byte little-endian size of the rest of the file and the form type WEBP. One or more chunks follow, each a 4-character ID, a little-endian size and the data, padded to an even length.

A simple lossy image has a single VP8 chunk (with a trailing space), and a simple lossless image a single VP8L chunk. The extended format starts with a VP8X chunk of flags and the canvas size, and may add ICCP (colour profile), ALPH (alpha for a lossy image), ANIM and ANMF (animation and its frames), EXIF and XMP .

  1. 0RIFF header, size, form type WEBP12 bytes
    1. 12VP8X flags and canvas size, extended format only18 bytes
    2. …ICCP, ANIM … optional chunksvaries
    3. …VP8 or VP8L the image, or ANMF framesvaries
    4. …EXIF, XMP optional metadatavaries
A WebP file: chunks inside a RIFF container