What is Favicoo?
Favicoo is a browser-native tool that converts PNG, JPG, and JPEG images into .ICO favicon files — instantly, privately, and for free. There are no servers, no uploads, and no accounts. Your images are processed entirely inside your browser.
It's part of RuntimeHub, a growing collection of free, privacy-first web utilities built under the RuntimeZero philosophy: powerful tools that run entirely in the browser, with zero server involvement and zero data collection.
Why we built it
Every developer and designer has been there: it's 11pm, you're about to deploy a site, and you still need a favicon.ico. The tools you find via search are either bloated, slow, require an email login, or quietly upload your files to a third-party server.
Favicoo exists to fix that. It's fast, it's honest about what it does, and it respects your files. The ICO assembler is written from scratch in vanilla JavaScript — no dependencies, no black boxes.
How the ICO format works
An .ico file is a container format that can hold multiple image resources at different resolutions. When a browser encounters a favicon, it picks the best resolution for the current display context — 16×16 for browser tabs, 32×32 for taskbar shortcuts, 512×512 for PWA install prompts, and so on.
Favicoo embeds each selected size as a full PNG stream inside the ICO container, preserving transparency and using 32-bit colour. The result is a modern, high-quality .ico file that works across every browser and operating system.
The RuntimeHub ecosystem
Favicoo is one tool in a growing suite. RuntimeHub hosts free browser-native tools for image processing, AI inference, document handling, audio conversion, and more — all sharing the same zero-upload, zero-server philosophy. Explore the full collection at runtime-hub.com.
Contact & feedback
Favicoo is maintained by the RuntimeZero team. If you find a bug, have a feature request, or just want to say hi, reach out via RuntimeHub. We read every message.