app/Config/Mimes.php
public static function guessTypeFromExtension(string $extension)
	{
		$extension = trim(strtolower($extension), '. ');

		if (! array_key_exists($extension, static::$mimes))
		{
			return null;
		}

		return is_array(static::$mimes[$extension]) ? static::$mimes[$extension][0] : static::$mimes[$extension];
	}
public static function guessTypeFromExtension(string $extension)
	{
		$extension = trim(strtolower($extension), '. ');

		if (! array_key_exists($extension, static::$mimes))
		{
			return null;
		}

		return is_array(static::$mimes[$extension]) ? static::$mimes[$extension][0] : static::$mimes[$extension];
	}
Attempts to determine the best mime type for the given file extension.

@param string $extension

@return string|null The mime type found, or none if unable to determine.