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ICO Converter

Details

How to use ICO Converter

What the tool does, how to run it, and what to expect from the result.

How to convert a PNG or JPG to an ICO file

An ICO file is a container that holds several square images at different sizes. Windows and browsers pick whichever entry fits the context, which is why a good favicon is one file with a 16px, 32px, and 48px version inside rather than a single scaled-down PNG.

This converter builds that container in your browser. It renders your source image at each size you tick, compresses each one as a PNG, packs them into a valid ICO, and verifies the header before handing you the file.

  • Choose a square PNG or JPG. A transparent PNG keeps its transparency.
  • Tick the sizes you need. 16, 32, 48, and 256 are pre-selected and cover most uses.
  • Click Build ICO and wait for the sizes to render.
  • Click Download ICO. The file is named after your source image.
  • Drop the file at the root of your site as favicon.ico, or point at it with a link rel=icon tag.
Tips

Getting a better result out of ICO Converter

Specific settings and thresholds, not general advice.

  • A non-square source is fitted inside the square icon rather than stretched, so a 1200x600 banner keeps its proportions and is padded with transparency. Crop to 1:1 first if you want it to fill the icon edge to edge.
  • For a classic favicon.ico, 16x16, 32x32, and 48x48 cover browser tabs, bookmark bars, and the Windows taskbar. 256x256 is what Windows Explorer uses for large tile views, and it is the one people forget.
  • Entries are stored as PNG data inside the ICO container, which every browser and Windows Vista or newer reads. If you must support Windows XP or some very old icon editors, they expect BMP entries and will not render these.
  • The 256x256 entry is written with a width and height byte of 0, which is not a bug: the ICO format stores dimensions in a single byte, so 256 is encoded as 0 by specification.
  • Alpha survives the conversion because each entry is a PNG. Start from a PNG with a transparent background if you want a rounded or non-rectangular icon, since a JPG source has no transparency to preserve.
Limits

What ICO Converter does not do

The honest boundary, so you do not lose time finding it yourself.

  • Only PNG and JPG sources are accepted. SVG, HEIC, and WebP are rejected by the file picker.
  • Sizes are fixed to 16, 32, 48, 64, 128, and 256. You cannot enter a custom pixel size.
  • It fits a non-square source inside the square rather than cropping it, so wide art leaves transparent margins.
  • It writes ICO only. It does not produce .icns for macOS or a full favicon package with a web manifest.
Reference

Terms used on this page

Short, plain-language definitions for the formats and settings above.

Files & formatsFaviconA favicon is the small icon a browser shows next to a site’s name in tabs, bookmarks, and history. It is usually a tiny square image (commonly an ICO, PNG, or SVG) and is one of the smallest files a website serves.General
At a glance

Who ICO Converter is for

A quick way to understand who this helps, what it solves, and where it connects next.

Best fit

Developers building Windows or favicon icons.

Ideal for

Using the ico converter without installing anything or signing up.

FAQ

Common questions

Short answers for the questions people usually have before trying a utility like this.

Which sizes belong in a favicon.ico in 2026?

16, 32, and 48 are the practical set: 16 for the browser tab, 32 for high-DPI tabs and the Windows taskbar, 48 for the desktop and some search result chips. Adding 256 costs a few KB and makes the file usable as a Windows application icon too. Anything beyond that is rarely read.

What happens if my image is not square?

It is scaled to fit inside the square and centred, with transparent padding on the short sides, so nothing is distorted. If you would rather the art filled the icon completely, crop it to 1:1 before converting.

Why is the file so small compared to other ICO converters?

Each icon entry is stored as a compressed PNG rather than an uncompressed 32-bit BMP. A 256x256 BMP entry alone is about 256KB before the mask, while the PNG equivalent of a simple logo is often under 10KB. Windows and every modern browser read PNG entries natively.

Can I use this to make a macOS app icon?

No. macOS uses the .icns container, which this tool does not write. ICO is a Windows and web favicon format. For an app icon you also need the specific rounded-square masks Apple expects, which is a design step, not a format conversion.

Is the ICO checked before I download it?

Yes. After the container is packed, its header is verified against the number of entries that were written, and the download only appears if that check passes. If a browser fails to encode one of the PNG entries you get an error message instead of a broken file.

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