Convert PNG to ICO
Build a favicon.ico holding several square sizes at once, from a PNG, in your browser. Transparency is preserved in every size.
Drop PNG files here or paste from the clipboard.
Your files are processed on this device. Nothing is uploaded.
What actually changes
An ICO isn’t a single image, it is a small container holding several images at different sizes so the operating system or browser can pick the one it needs. Converting writes each size you tick as its own PNG and assembles them into one file with a directory at the front. Transparency is preserved throughout. The original aspect ratio isn’t: icons are square, so a non-square source is fitted into a square and the edges are padded.
| PNG | ICO | |
|---|---|---|
| Compression | Lossless | Lossless |
| Transparency | Yes | Yes |
| Format can be animated | No | No |
Detail disappears long before 16 pixels
A logo that reads beautifully at 512 pixels is frequently an unidentifiable smudge at 16, which is the size a browser tab actually uses. Thin strokes vanish, text becomes texture and anything with more than two or three shapes turns to mush. The fix isn’t technical: design a simplified mark for the small sizes, usually a single letter or one bold shape and check it at actual size rather than zoomed in.
What is actually in the file
Six bytes of header, then sixteen bytes per image describing its size, its length and where it starts, then the images one after another. Old ICO files stored raw bitmaps with a separate transparency mask, which is why ancient icons have hard jagged edges. Every current system accepts PNG inside the container instead, which is what this page writes and that is where the smooth transparency comes from.
You can confirm it yourself: an ICO built here begins with the bytes 00 00 01 00 and
each image inside begins with the PNG signature.
Checking it at real size
Zoom out until the icon is the size of a favicon on your screen or better, build the file and look at it in an actual browser tab next to your other tabs. Almost every icon that fails does so because it was only ever judged at 200 pixels wide.
The rest of the icon set
A favicon is one piece. A site usually also wants a 180 pixel PNG for iOS home screens and a 192 and 512 pixel pair for Android and PWA manifests. Those are plain PNGs rather than ICO files, so the resizer handles them: set an exact square size and export each one.
Common questions
Which sizes should I include?
16, 32 and 48 covers browsers and Windows comfortably and that is what this page ticks by default. Adding 64, 128 and 256 makes the file larger but covers high-density displays and large icon views. There is no penalty beyond file size and an ICO with six sizes is still only a few tens of kilobytes.
Do I still need a favicon.ico in 2026?
It is still the most reliable single file. Browsers request /favicon.ico by default even with no markup and it is what appears in bookmarks, history and the tab. Most sites pair it with a larger PNG and an SVG declared in the HTML, but the ICO remains the fallback that always works.
Can an ICO have a transparent background?
Yes and it should. Each image inside the container is stored as a PNG here, which carries a full alpha channel, so the icon sits correctly on both light and dark backgrounds. A white square behind your logo will be obvious in a dark themed browser.
Should my source image be square?
Yes, ideally exactly square and at least 256 pixels. A rectangular source has to be fitted into a square, which means padding at the sides and a logo that looks smaller than everyone else's in the same tab strip.