ICO to AVIF: Complete Conversion Guide for Web & Icons

By Bill Crawford  ·  March 2026  ·  8 min read  ·  Last updated March 6, 2026

Connect on LinkedIn →

What Is the ICO Format?

ICO is a container image format native to Windows, introduced with Windows 1.0 in 1985. Its defining feature is the ability to store multiple images of different sizes and color depths inside a single file. When Windows displays a file's icon in Explorer, or a browser renders a website's favicon in a tab, it reads the ICO container and selects the frame that best fits the display context — the 16×16 frame for a compact tab favicon, the 256×256 PNG frame for high-DPI or extra-large icon views.

A modern ICO file typically embeds PNG frames at 16×16, 32×32, 48×48, 64×64, 128×128, and 256×256 pixels. Older ICO files may use uncompressed BMP frames, but contemporary tools universally use PNG. ICO with PNG frames supports full 32-bit RGBA color, meaning transparency is preserved across all embedded sizes.

What Is AVIF?

AVIF (AV1 Image File Format) is a modern image format derived from the AV1 video codec, developed by the Alliance for Open Media — a consortium including Google, Apple, Mozilla, and Amazon. AVIF was finalized as a specification in 2019 and has since achieved broad browser support.

AVIF's main advantage over older formats is compression efficiency. At the same visual quality, AVIF files are typically 50% smaller than JPEG and 30–40% smaller than WebP. AVIF supports both lossy and lossless compression, full alpha channel transparency, HDR color, and wide color gamuts. It is now the recommended format for web images in performance-sensitive contexts.

When Should You Convert ICO to AVIF?

The ICO format is purpose-built for icons and favicons. It is not a general-purpose web image format. Converting ICO to AVIF makes sense in several specific scenarios:

• Web display outside favicon context. If you want to display a brand icon or logo — originally delivered as an ICO — as a regular image in a webpage, AVIF gives you a modern, compressed format that renders correctly at any size.
• Progressive image pipelines. Teams that manage image assets programmatically may receive ICO files from design tools and need to convert them into a web-ready format for use in Next.js, Astro, or other frameworks that support AVIF natively.
• Legacy asset migration. Organizations migrating from old Windows-centric icon libraries to modern web stacks may have large collections of ICO files. Converting to AVIF standardizes the image format while preserving the icon art at the highest available resolution (typically 256×256).
• Open Graph and social image use. Some tools extract favicon ICOs from websites and need a standard web image format. AVIF is a valid target for this kind of repurposing.
• Mobile apps and PWAs. Progressive Web Apps sometimes use AVIF for app icons and splash screens. If your existing icon art is in ICO format, converting to AVIF enables use in modern manifest configurations.

ICO vs AVIF: Format Comparison

Choosing a Quality Setting

ICO files contain icon art — logos, symbols, and graphic marks — rather than photographs. This distinction matters when choosing a quality setting for AVIF output:

• Quality 85–95: Recommended for most icon-to-AVIF conversions. Icon art typically contains flat colors, sharp edges, and fine text that are sensitive to compression artifacts. A higher quality setting preserves these characteristics.
• Quality 75–85: Suitable for icons that will be displayed at medium to large sizes on screen, where some compression is acceptable. Good balance of file size and visual fidelity.
• Quality 60–75: Only appropriate for decorative icons where exact color accuracy is not required, or where file size is the primary constraint.

The default quality setting of 80 in our tool is a good starting point for most icon art. Preview the output before settling on a final quality value — the difference between 80 and 90 is often significant for logos with thin strokes or text.

Transparency in ICO and AVIF

Most modern ICO files use 32-bit RGBA PNG frames, which support full alpha channel transparency. When your browser loads an ICO file to a canvas element — the mechanism used by our conversion tool — the alpha channel is preserved in the canvas pixel data. The AVIF encoder then reads that pixel data, including the alpha values, and writes them into the AVIF output.

The result: transparent areas in your ICO icon art will remain transparent in the AVIF output. This is particularly important for logos, icons with irregular shapes, and any artwork designed to display over different backgrounds.

AVIF Browser Support

AVIF support has matured significantly since 2021. As of early 2026, the major browser support landscape is:

• Chrome: Full AVIF support since version 85 (August 2020).
• Firefox: Full AVIF support since version 93 (October 2021).
• Edge: Full AVIF support since version 121 (January 2024).
• Safari: AVIF support added in version 16.4 (March 2023).
• iOS Safari: AVIF supported since iOS 16.4.

For maximum compatibility when using AVIF images on the web, use the HTML <picture> element to provide a fallback:

<picture>
  <source srcset="icon.avif" type="image/avif">
  <source srcset="icon.webp" type="image/webp">
  <img src="icon.png" alt="Icon">
</picture>

Privacy: Why Browser-Based Conversion Matters

ICO files often contain proprietary brand assets — company logos, product icons, and trademarks. Uploading these files to a third-party server for conversion creates an unnecessary copy of sensitive brand assets outside your control. Our ICO to AVIF converter runs entirely in your browser using the Canvas API. Your files never leave your device — the conversion happens in memory and the output is downloaded directly from your browser.