Difference Between libavif and AVIF Explained

This article provides a clear comparison between AVIF and libavif, outlining their distinct roles in digital imaging. While AVIF is a cutting-edge image file format, libavif is the open-source software library used to create and read those files. Understanding the difference between the format standard and its implementation library is crucial for developers and content creators adopting next-generation web images.

What is AVIF?

AVIF, which stands for AV1 Image File Format, is a file format specification. It is a standard for storing compressed still images and image sequences.

• The Technology: AVIF uses the AV1 video compression codec inside the ISO Base Media File Format (ISOBMFF) container.
• The Purpose: It was designed to replace older formats like JPEG, PNG, and WebP by offering significantly smaller file sizes while maintaining or improving image quality.
• Features: AVIF supports high dynamic range (HDR), wide color gamut (WCG), transparency (alpha channels), lossless and lossy compression, and animated image sequences.

AVIF is not a piece of software; it is a set of rules and specifications that define how image data must be structured and compressed.

What is libavif?

libavif is a specific, open-source software library written in C. It is a tool created to write (encode) and read (decode) files that adhere to the AVIF specification.

• The Purpose: It acts as the engine that programs use to handle AVIF files. For example, web browsers, image editors, and operating systems use libavif behind the scenes to display .avif images on your screen or to save edited images in the AVIF format.
• The Creator: It is maintained by the Alliance for Open Media (AOMedia), the same consortium that developed the AV1 video codec.
• Functionality: libavif depends on external codecs (such as aom, dav1d, or rav1e) to perform the actual AV1 video compression and decompression, acting as the bridge that packages those compressed frames into the final .avif container.

The Key Difference: Format vs. Tool

The easiest way to understand the difference is through an analogy:

• AVIF is the blueprint. It defines what the final house should look like and how it should be structured.
• libavif is the construction crew. It is the actual tool that reads the blueprint to build the house (encoding) or opens the door so you can walk inside (decoding).

In summary, you view an AVIF image on a website, but the web browser uses libavif to render that image on your screen.