Detects the true image format of any URL via magic byte inspection — works even when the file extension or Content-Type header lies (common with proxied or CDN-hosted images). Returns: format (png/jpeg/gif/webp/avif/bmp/tiff/svg/ico/unknown), detected MIME type, whether Content-Type header matches, file size (bytes), and pixel dimensions for PNG and JPEG. No API key required. $0.050/call.