FileFormat

FileFormat[source] attempts to determine what Import format could be used to import the file.

FileFormat[source, {fmt1, fmt2, ...}] returns the first format that can be used.

Examples

Detect file format:

FileFormat["image.png"]
(* "PNG" *)

Check from multiple formats:

FileFormat["data.csv", {"CSV", "TSV", "JSON"}]
(* "CSV" *)

Please visit the official Wolfram Language Reference for more details.