What image formats exist (JPG, PNG, WebP)? How does the browser choose which format to use?

There are different image formats, the most popular ones are:

• JPG (JPEG) — lossy compression, suitable for photographs where compression is important but perfect clarity is not.
• PNG — lossless compression, supports transparency (alpha channel), suitable for graphics, icons, where clarity and transparency are important.
• WebP — a modern format from Google, supports both lossy and lossless compression, as well as transparency. Often provides smaller file sizes while maintaining quality.

How browsers choose the format:

1. The server can send different formats depending on the Accept header in the HTTP request, which indicates what formats the browser supports.
2. For example, if the browser supports WebP, it will indicate this in Accept: image/webp, and the server can serve WebP instead of JPG or PNG.
3. If the server does not support dynamic format delivery, the browser loads the image in the format specified in HTML/CSS.

Thus, the format choice depends on browser support and server settings. Adaptive delivery of formats via CDN or server configurations is often used for optimization.