What is an ICO file and what is it for?
ICO is the Windows icon format and the classic favicon format, the small icon shown in the browser tab. Unlike a PNG, an ICO file stores several versions of the same image at different sizes, such as 16, 32, 48 and 256 pixels, and the system picks the one that fits each place: the tab, the taskbar, the desktop or File Explorer.
This tool creates an ICO from a PNG, JPG or WebP and lets you choose exactly which sizes to include. Each size is made by scaling the image down in steps, so small icons look clean instead of pixelated. You can keep transparency or add a background colour, add an inner margin and decide what happens when the image is not square: fit it whole or crop it to fill the icon.
Sizes up to 128 px are stored as BMP, which every version of Windows reads, and the 256 px size as PNG, as Windows’ own icons do, so the file stays small. Everything happens in your browser: the image is never uploaded to a server. With ToolStudio Pro you can convert many images at once and download them in a ZIP.
How to convert a PNG to ICO
- Drop your PNG image into the tool or click to choose it.
- Choose the ICO sizes: “Favicon” (16, 32 and 48), “Windows” or any sizes one by one.
- Pick a transparent or coloured background and, if you like, add an inner margin.
- Click “Create ICO”, check the preview of each size and download the .ico file.
When to use this tool
- Create your website’s favicon.ico from the PNG logo.
- Make an icon for a folder, shortcut or program on Windows.
- Prepare the icon of a desktop app (Electron, .NET, Python with PyInstaller).
- Turn a rectangular logo into a square icon without distorting it.
Which sizes should the ICO include?
- Website favicon: 16, 32 and 48 px. This is what browsers and Google ask for.
- Windows icon: 16, 24, 32, 48, 64 and 256 px, so it looks right on the taskbar, desktop and File Explorer.
- If your image has fine detail, check the 16 px preview: at that size a simple design works best.
Formats
- Input: PNG, JPG, WebP, GIF, BMP, AVIF, SVG and ICO. A square image of at least 256 px works best.
- Output: one .ico file with 32-bit icons and transparency, from 16 to 256 px.
Frequently Asked Questions
Is my image uploaded to a server?
No. The ICO is created in your browser and the image never leaves your device.
Is the PNG transparency kept?
Yes. Icons are saved in 32 bits with an alpha channel, so transparent areas stay transparent. You can also choose a background colour.
What if my image is not square?
You can fit it whole inside the icon, leaving transparent margins, or crop it to fill the whole square. The image is never stretched.
Can I use the ICO as a favicon?
Yes. Choose the “Favicon” preset (16, 32 and 48 px), save the file as favicon.ico in the root of your site and link it with <link rel="icon" href="/favicon.ico">. For mobile icons too, use the app icon generator.
What is the largest ICO size?
The ICO format supports icons up to 256 × 256 pixels, the size Windows uses for large desktop and File Explorer icons.
Can I convert several images to ICO at once?
Yes, with ToolStudio Pro. Add as many as you like; they are converted with the same settings and downloaded together in a ZIP. The free try covers one image.
Is it free?
You can try it for free with one image and change the settings as often as you need. For unlimited and bulk use, ToolStudio Pro costs €1.99 a month and includes every tool.