Compress ICO favicons in your browser
An .ico is a bundle of images. We rewrite each one as an optimised PNG and drop the entries your visitors never request.
or browse your device. Everything is processed on this device
No ICO to hand?
How to compress an ICO
We read the icon directory and list what is actually inside it. Nothing is uploaded.
Up to 64px is the safe default. Every entry you drop is bytes every visitor stops downloading.
Each entry comes back as an optimised PNG inside a freshly written container.
What is inside an .ico file?
An .ico is not an image, it is a directory of images. The header lists how many entries the file holds, and each entry says how wide it is, how deep its colour is, and where its data starts. The data itself is either a whole PNG file or a headerless Windows bitmap whose stored height is doubled, because the rows underneath the picture are a one bit transparency mask left over from Windows 3. Everything expensive about the format comes from that second option: a raw 256 by 256 bitmap entry is 256KB on its own.
The two levers are therefore obvious once you can see inside the file. Store each entry as a PNG instead of a bitmap, which the format has allowed since Windows Vista and every browser supports. Then throw away the entries nobody asks for. A generated favicon commonly ships 16, 32, 48, 64, 128 and 256, and browsers request the small ones. The 256px entry exists for the Windows desktop, and if your icon is going on a website rather than into a program shortcut, it is pure weight.
The wider point: a modern favicon is a small PNG and an SVG, declared in your HTML, and the .ico exists only for old Internet Explorer and for Windows shell integration. If you have no reason to support either, you can serve a 32px PNG and an SVG and skip this format entirely. If you do need it, this tool will make the one you have considerably smaller.
Favicon and ICO FAQ
How do I make a favicon smaller?
Two things, in this order. Drop the entries you do not need, which usually means the 128px and 256px ones no browser requests. Then make sure each remaining entry is stored as a PNG rather than a raw bitmap, since a raw entry is width times height times four bytes with nothing done to it. This tool does both, and cuts the palette on top.
What sizes does a favicon need?
16, 32 and 48 cover everything that still reads .ico. 16 is the classic tab and address bar icon, 32 is what high density displays and the Windows taskbar use, and 48 is the Windows shell. Anything larger is for desktop shortcuts, and anything you add beyond that is downloaded by nobody.
Why is my .ico file so big?
Almost always because it holds a 256 by 256 entry stored as a raw uncompressed bitmap. That single entry is around 256KB before anything else in the file is counted. Older favicon generators emitted them by default, which is why a 16px icon can somehow weigh a quarter of a megabyte.
Is an .ico file still needed in 2026?
Only for Internet Explorer and Windows shell integration. Every current browser will take a PNG or an SVG declared with a link tag, and most sites now ship exactly that plus a small .ico at the site root for anything old that goes looking for one out of habit.
Will this break my favicon?
No. The output is a valid ICO written from scratch, with the same entries in the same order, each one re-encoded as a PNG. PNG entries inside an .ico have been supported since Windows Vista and are read by every browser. The only change you can choose to make is dropping sizes, and we tell you exactly which ones went.
Does it keep transparency?
Yes. Old bitmap entries store their transparency in a separate one bit mask, which we read and apply, and the PNG entries we write carry a full alpha channel. Antialiased edges survive.
Can it add a size that is not already in the file?
No. This is a compressor, not a generator: it only ever keeps or drops what is already there. Upscaling a 32px entry to make a 256px one would produce a blurry icon and a bigger file, which is the opposite of the job. If you need a size the file does not have, go back to the artwork.
Other compressors
Same format joins the queue. Anything else re-routes to its own tool.