An ICO file is a container that holds the same icon at several sizes, so the system can pick the one that fits. This converter writes six sizes into one file: 16 and 32 pixels for browser tabs and small Windows icons, 48 and 64 for desktop and explorer views, and 128 and 256 for large icon views and high density screens. This page opens with ICO as the output; drop a PNG and convert. Start from a square image of at least 256 by 256 pixels with a transparent background. A non-square image is fitted inside the square and centred with transparent edges, and a small source will look soft at the larger sizes because nothing can add detail that is not there. Detailed artwork rarely survives at 16 pixels, so logos with a simple, bold mark work best; some designers make a simplified version just for the small sizes. For a website, place the file at the root as favicon.ico, which browsers request automatically, and reference it with a link tag in the page head. Modern browsers also accept PNG favicons, but favicon.ico remains the safest default. For the full set of favicon files and HTML tags use Favicon Generator, and for vector logos start with SVG to PNG Converter.
Choosing the right image format for web use has a significant impact on file size and quality. JPEG (Joint Photographic Experts Group) uses lossy compression optimized for photographs: it discards subtle color gradients in ways the human eye does not easily notice, achieving compression ratios of 10:1 to 20:1 at acceptable quality. PNG (Portable Network Graphics) uses lossless compression and supports full transparency (alpha channel), making it ideal for logos, icons, screenshots, and images with sharp edges or text. WebP is Google's modern format that achieves better compression than both JPEG and PNG at equivalent quality: typically 25 to 35 percent smaller than JPEG at the same quality setting, and 26 percent smaller than PNG for lossless images. WebP also supports transparency like PNG. GIF (Graphics Interchange Format) is the oldest format still in use, primarily kept alive by its support for animation. For still images, GIF is inferior to PNG in both quality and compression, limited to 256 colors per frame. Converting to WebP for web delivery is the most impactful single optimization for image-heavy sites. Browser support for WebP is now essentially universal (Chrome, Firefox, Safari 14+, Edge). For cases where legacy Safari support is required, serving WebP via a picture element with a JPEG fallback provides the best result across all browsers.