twineconvert

free · in-browser · no upload

ICO to AVIF
Converter

Drop your ICO file. We'll convert it to AVIF right here in your browser, your file never leaves your device.

or drop your file

Select your file here to get started

or drop your file here.

Accepts .ico

nothing uploaded no file size cap no signup

How it works

Three steps. No upload, no signup.

  1. 1

    Drop your file

    Click the dropzone above or drag a ICO from your desktop. Files of any size, there's no upload, so there's no upload limit.

  2. 2

    Convert in your browser

    The conversion runs entirely in this tab using JavaScript and WebAssembly. Your file never touches our servers, we don't have any.

  3. 3

    Download

    Get your AVIF the moment the conversion finishes. Convert another, or close the tab.

Files stay on your device

Your file is never uploaded. The entire conversion runs in your browser using WebAssembly. We can't see what you convert because we have no server to see it.

No file size limit

Server converters cap free users at 1-2 GB and gate larger files behind a paid plan. Since nothing uploads, our limit is whatever your browser can handle.

Free, no signup, no ads on conversions

No account required. No watermark on the output. No queue. Drop a file, get a converted file.

Why convert ICO → AVIF

What this conversion is actually for

AVIF is the newest web image format, typically 20 percent smaller than WebP and far smaller than PNG or JPEG at the same quality, with alpha transparency. This converts ICO images to AVIF entirely in your browser, so the file never leaves your device. Source transparency is preserved.

A real example

You have a ICO image and need AVIF for a site, app, or workflow that requires it. Drop the ICO here and download the AVIF, no upload.

Troubleshooting

An older browser will not open the AVIF.

AVIF is supported in all current browsers; very old versions may not decode it. The output is a standard AVIF you can verify by re-opening it here.

Formats involved

About ICO and AVIF

ICO, Icon

ICO is Microsoft's icon format, a single file containing the same icon at multiple sizes (typically 16, 32, 48, 64, 128, 256 pixels). Browsers use the favicon at the top of every tab. Modern websites can use PNG favicons too, but ICO remains the universally-supported choice especially for older browsers and Windows desktop integration.

How to open

Browsers and Windows recognize ICO natively. macOS treats them as standard images. Modern image editors read multi-resolution ICOs; some older tools only see the first size.

Full ICO format guide →
AVIF, AV1 Image File Format

AVIF uses AV1 video codec compression for still images, typically 30-50% smaller than JPG and 20% smaller than WebP at the same visual quality. Supported in Chrome since 2020, Firefox since 2021, Safari since 16.4 (2023). The encoding step is significantly slower than JPG, which is why CDNs adopt it slowly. Best fit: hero images and photo galleries on modern sites where bandwidth matters.

How to open

All current browsers (2024+) display AVIF inline. Native OS viewer support varies, Windows 11 supports it natively, macOS only since Ventura. Older photo editors may need a plugin.

Full AVIF format guide →

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FAQ

Common questions

Is this ICO → AVIF converter really free?

Yes. No signup, no watermark, no daily file count limit. Every conversion runs in your browser, your file never touches our servers because there are no servers.

Where does my file go when I convert it?

Nowhere. The conversion runs entirely in your browser using JavaScript and WebAssembly. Your file is never uploaded to our servers. We don't have any servers handling files, there's nothing for us to log, store, or accidentally leak.

What's the maximum file size?

Whatever your browser can hold in memory. Practically, this means a few hundred MB on most computers, significantly larger than the 1-2 GB caps that server-upload converters charge for. Very large files (multi-GB) may require closing other browser tabs first.

Why convert ICO to AVIF?

Browser favicons and Windows desktop icons. Modern web images where every kilobyte matters. The most common reason to convert is compatibility, AVIF works in places where ICO doesn't, or vice versa.

How do I open a ICO file in the first place?

Browsers and Windows recognize ICO natively. macOS treats them as standard images. Modern image editors read multi-resolution ICOs; some older tools only see the first size.

Does this work offline?

Once the page is loaded, the conversion itself runs entirely offline. The first time you use a tool, your browser downloads the conversion library (a one-time cache). If you reload while offline, the page won't load, but you can install the site as a Progressive Web App for full offline use.

Can I convert multiple files at once?

Single file at a time for now. Batch conversion is on the roadmap, for now, drop one file, download the result, then convert the next.