Compress ICO Icons
An ICO bundles several sizes of one icon, and its 256 px image, often stored as an uncompressed bitmap, can make up most of the file. Browsers only use the small sizes for a favicon, so rebuilding the icon with 16, 32 and 48 px images, each PNG-compressed, typically cuts a favicon.ico to a few kilobytes.
- Processed locally
- No upload, no wait
- No sign-up
- No watermark
Drop images here
or choose files · paste with Ctrl/⌘ V
ICO expected · other image formats also work
How to use Compress ICO
- 1
Drop your images, choose files, or paste from the clipboard.
- 2
Adjust the options. The preview updates as you change them.
- 3
Click Compress. Files are processed on your device.
- 4
Download each result or everything as a ZIP.
Why use Aback Images for compress ico
Best-in-class encoders
MozJPEG for JPG, OxiPNG and palette quantisation for PNG, libwebp and libavif for WebP and AVIF, all compiled to WebAssembly.
Live before/after
See the result and its file size on your actual image before processing the batch.
Processed on your device
Your images are decoded, edited and encoded inside this browser tab by Web Workers. Nothing is uploaded to a server.
Never bigger than the original
If compression cannot beat your file, the original is returned unchanged with a note.
Related tools
Every favicon and touch icon size, a multi-size favicon.ico, web manifest and HTML snippet in one ZIP.
Convert PNG to ICO in your browser, multi-size icons for favicons and Windows. Batch, private, no uploads.
Convert ICO to PNG in your browser, ready for screenshots, logos, graphics and anything that needs transparency. Batch, private, no uploads.
Resize images to exactly 32×32 px on a transparent square, sharp and unstretched, for favicons, bookmarks and small icons.
Shrink JPG, PNG, WebP, AVIF and GIF files with MozJPEG, OxiPNG and modern codecs, with a live before/after preview.
Make JPEG photos smaller with MozJPEG, the encoder that beats standard JPEG by 10-15% at the same quality.
Cut PNG size by up to 80% with smart palette reduction and OxiPNG lossless optimisation, keeping transparency.
Re-encode WebP images smaller with libwebp's best settings, including animated WebP.
Frequently asked questions
Will Windows still show a sharp icon?
For favicons, yes. Desktop shortcuts and large icon views can use a 256 px image; if your ICO is for a Windows program, build it with PNG to ICO and keep the larger sizes.
Does the ICO keep transparency?
Yes. Each size is a 32-bit PNG with a full alpha channel.
Are my images uploaded anywhere?
No. Processing happens inside your browser with WebAssembly and Web Workers. The site only downloads the app code and codecs; your files never leave your device. You can confirm this with the live upload counter on the tool, or in your browser's network panel.
Can I process many files at once?
Yes. Drop a whole selection or folder. Files are processed in parallel on several worker threads, each result can be downloaded on its own, and everything can be saved as one ZIP.
Is it free? Is there a file limit or watermark?
It is free with no account, no watermark and no daily limit. The only limit is your device's memory: very large images (over roughly 100 megapixels) may be refused to keep the tab from crashing.