Favicons and ICO files explained
A favicon is a small browser identity image. An ICO file can package raster icon images, but the file extension alone does not create a useful icon set.
What an ICO file contains
ICO is a container for one or more image entries used for Windows icons and browser favicons. Older files often use bitmap image data; modern ICO files can also contain PNG-encoded entries. A multi-entry file can provide different pixel sizes so software can choose an image suited to its display context.
An ICO file can contain several sizes, but MEZENCORE exports one image entry from the processed PNG. The dimension control can limit the source’s longest edge; it does not create a 16-, 32-, and 48-pixel set. For a multi-size ICO, use a tool that lets you create and inspect each entry.
Start with a simple source
Design the icon so its main shape remains recognizable at a tiny size. Avoid relying on hairline strokes, small lettering, or several low-contrast details. A brand mark may need a compact variant drawn specifically for browser tabs; shrinking a full logo with a long wordmark can make it unreadable.
Use a square source for a conventional app or favicon shape and leave visual breathing room at its edges. Check transparency against both light and dark browser chrome. A white symbol with transparent surroundings can disappear on a light background; a dark symbol can disappear on a dark one. Provide a contrasting solid or alternate mark if the destination cannot adapt automatically.
Choose the right output for the site
Many sites use SVG or PNG for modern favicons and keep ICO for systems that request it. SVG scales when supported by the browser; PNG has a fixed pixel size. Microsoft lists 16, 32, 48, and 256 pixels as common ICO resource sizes for Windows icons. These are platform examples, not universal browser requirements. See Microsoft’s icon documentation. The required files and markup depend on your site framework and hosting setup. Check the published paths; browsers may continue to show a cached favicon for a while.
MEZENCORE itself links an SVG favicon in each page head. The downloadable ICO option is separate from the site’s own favicon and produces a single-entry ICO image from a processed raster. Use it for a single icon image, not to generate a complete favicon set.
Check the result at actual size
View the exported icon at its intended size. A logo that looks clear when large may become an indistinct shape at 16 pixels. Check corners, gaps, and transparent areas against the light and dark backgrounds where it will appear.
Prioritize a clear shape at actual size over a small file. If the ICO looks wrong or has unsuitable dimensions, use an icon tool that lets you set entry sizes and transparency.
MEZENCORE’s ICO behavior
When opening an ICO, MEZENCORE uses its first available image entry. Its ICO export wraps the processed PNG in a single-entry container; you cannot choose separate icon sizes.
For ordinary image exports, use the format cheat sheet. If your icon seems too large, see why compression may not shrink it. When you are ready, try the optimizer with a copy of the source.