Convert PNG to ICO in your browser

Because it holds more than one image. A favicon.ico with 16, 32 and 48px entries is three complete pictures in one file, so it is roughly the sum of three PNGs plus a small directory. That is the format working as designed, not a compression failure. If the size matters, the largest entry costs the most, so stay on the 16, 32 and 48 ladder and cut the colours on a simple mark.

16, 32 and 48 covers everything that still reads an .ico: 16 for the tab and address bar, 32 for a high-DPI tab and the Windows taskbar, 48 for the Windows shell. The 256px entry that most generators add is for desktop icons, is usually most of the file, and no browser has ever requested it. It is offered here as a choice rather than included by default.

It is scaled to fit inside the square and centred, with the space around it left transparent. Nothing is cropped away. That keeps the whole mark visible but leaves it smaller in the frame than it could be, so if the icon needs to fill the square, crop the PNG to a square before you convert it.

Yes. Every entry is stored as a 32-bit PNG inside the icon, which keeps the full alpha channel, so a logo meant to sit on a dark or coloured background still will. This is also why the entries are PNG rather than the raw bitmaps older .ico files use: those carry a one-bit mask that turns soft edges into jagged ones.

At the root of your site, named favicon.ico, so it answers a request for /favicon.ico. You can also point at it explicitly with a link tag, but the reason to keep the conventional name and location is the clients that never read your markup and just ask for that path.

No. The PNG is decoded and the ICO is written by your own browser, in this tab. There is no upload endpoint in the site for a file to go to, which you can check in your network tools: convert something and watch that no request carries it. Disconnect from the network after the page loads and it still works.

Yes, every time, and there is no way to turn it off. The image is decoded to pixels and encoded again from those pixels alone, so EXIF and GPS, the XMP packet, embedded colour profiles, and any Content Credentials or AI-generation tags the file arrived with do not survive. There is no switch for this, because there is no way to keep them. What no compressor can remove is a watermark written into the pixels themselves, such as the invisible marks some image generators add: those survive re-encoding here and everywhere else.