SealedMedia SoftSeal GIF

import magic
# Libmagic lacks definitions for the proprietary SoftSeal container. It will likely identify the file as 'application/octet-stream'.
print(magic.from_file('secure_image.sgif', mime=True))

const mime = require('mime');
// Standard JS MIME libraries map this purely based on historical IANA registry associations if the extension is recognized
console.log(mime.getType('secure_image.sgif')); // May output 'image/vnd.sealedmedia.softseal.gif' depending on the dictionary

import "net/http"
// The standard net/http library cannot detect sealed files internally via byte sniffing. You must rely on extension string matching.

$mime = mime_content_type('secure_image.sgif');
echo $mime; // Standard server environments will map this to application/octet-stream