What the generator produces
Drop one image and the page renders it at every size a modern site needs, shows a preview of the 16, 32, 48, 180 and 512 pixel versions, and packs the full set into favicons.zip. Inside the zip are PNG files at 16, 32, 48, 64, 192, 256 and 512 pixels, named favicon-16x16.png and so on, plus apple-touch-icon.png at 180x180, a favicon.ico, and snippet.html with the link tags to paste into the head of your pages. The snippet is also available with a Copy button. All rendering is done with the browser canvas; nothing is uploaded and no account is needed.
How the .ico file is built
The favicon.ico is not a single image. It is a container with three entries, 16x16, 32x32 and 48x48, each stored as a PNG inside the ICO directory structure. Browsers, Windows Explorer and bookmark managers pick the entry closest to the size they need, which is why the small sizes look crisp rather than being a scaled-down 256 pixel icon. The container is written byte by byte in JavaScript, with the standard six byte header, a 16 byte directory entry per image and the PNG payloads appended; it opens in any tool that understands modern ICO files. PNG-in-ICO has been supported by every major browser and by Windows since Vista, so it is a safe default for a website. A typical favicon.ico from a flat logo is 5 to 15 KB; from a photo it can reach 30 KB because PNG compresses photographic detail poorly.
What makes a good source image
Start with a square image of at least 512x512 pixels. The tool draws the source into a square canvas at each size, and a non-square image is stretched to fit, which distorts a wide logo into a squashed one. If your artwork is not square, trim it on the crop tool first or pad it to a square with a transparent background on the resize tool using Fit and pad with PNG output. Transparency is preserved in every PNG and in the ICO entries, so a logo can sit on light and dark browser tabs alike.
Simplicity matters more than resolution. At 16 pixels a wordmark becomes unreadable noise; a single letter, a bold glyph or a solid shape survives the downscale. Thin lines vanish, and gradients turn to bands. A good habit is to check the 16 and 32 pixel tiles in the preview before downloading, since those are what most visitors will actually see in the tab bar.
Installing the set
Upload the files from the zip to the root of your site so that /favicon.ico and /favicon-32x32.png resolve, then paste the four link tags from snippet.html into the head. The 180 pixel apple-touch-icon is what iOS uses when someone adds the site to their home screen; the 192 and 512 pixel PNGs are the sizes a web app manifest expects for Android, although the generator does not write the manifest file itself, so add those entries to your manifest by hand if you have one. Browsers cache favicons aggressively; if the old icon persists after you replace the files, hard refresh or append a version query to the href.
Limits
The page accepts JPG, PNG and WebP, and an SVG will load if the browser can render it, but complex SVG with external fonts may draw incorrectly. There is no editing of padding, background colour or rounded corners; prepare the artwork in an editor and use this page for the final export. The ICO holds only the three small sizes, which is the conventional set; if you specifically need an ICO with 64 or 256 pixel entries, the PNG to ICO converter writes a five-size container.