You can use an Online JPG Checker to confirm if a file truly follows the JPEG standard.

Because they load quickly, JPEGs remain the "gold standard" for web publishing and social media. Why "JPG" instead of "JPEG"?

The three-letter extension is a relic of older Windows operating systems that had a three-character limit for file extensions. Systems like Mac and Linux, which didn't have this limit, used .jpeg . Today, they are functionally identical and used interchangeably. Common Tools for Managing Images