Title: MimeType::toExtension
Published: May 20, 2026
Last modified: August 20, 2026

---

# MimeType::toExtension(): string

## In this article

 * [Return](https://developer.wordpress.org/reference/classes/wordpress-aiclient-files-valueobjects-mimetype/toextension/?output_format=md#return)
 * [Source](https://developer.wordpress.org/reference/classes/wordpress-aiclient-files-valueobjects-mimetype/toextension/?output_format=md#source)
 * [Changelog](https://developer.wordpress.org/reference/classes/wordpress-aiclient-files-valueobjects-mimetype/toextension/?output_format=md#changelog)

[ Back to top](https://developer.wordpress.org/reference/classes/wordpress-aiclient-files-valueobjects-mimetype/toextension/?output_format=md#wp--skip-link--target)

Gets the primary known file extension for this MIME type.

## 󠀁[Return](https://developer.wordpress.org/reference/classes/wordpress-aiclient-files-valueobjects-mimetype/toextension/?output_format=md#return)󠁿

 string The file extension (without the dot).

## 󠀁[Source](https://developer.wordpress.org/reference/classes/wordpress-aiclient-files-valueobjects-mimetype/toextension/?output_format=md#source)󠁿

    ```php
    public function toExtension(): string
    {
        // Reverse lookup for the MIME type to find the extension.
        $extension = array_search($this->value, self::$extensionMap, \true);
        if ($extension === \false) {
            throw new InvalidArgumentException(sprintf('No known extension for MIME type: %s', $this->value));
        }
        return $extension;
    }
    ```

[View all references](https://developer.wordpress.org/reference/files/wp-includes/php-ai-client/src/files/valueobjects/mimetype.php/)
[View on Trac](https://core.trac.wordpress.org/browser/tags/7.1/src/wp-includes/php-ai-client/src/Files/ValueObjects/MimeType.php#L116)
[View on GitHub](https://github.com/WordPress/wordpress-develop/blob/7.1/src/wp-includes/php-ai-client/src/Files/ValueObjects/MimeType.php#L116-L124)

## 󠀁[Changelog](https://developer.wordpress.org/reference/classes/wordpress-aiclient-files-valueobjects-mimetype/toextension/?output_format=md#changelog)󠁿

| Version | Description | 
| [0.1.0](https://developer.wordpress.org/reference/since/0.1.0/) | Introduced. |

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