wp_get_attachment_url( int $attachment_id )

Retrieve the URL for an attachment.

Parameters

$attachment_id

(int) (Optional) Attachment post ID. Defaults to global $post.

Return

(string|false) Attachment URL, otherwise false.

More Information

You can change the output of this function through the wp get attachment url filter.

This function will not URL encode the URL. If you have attachments with invalid characters in their name, you should raw URL encode the output of this function in order to have a valid URL.

Sample code that gives you a root-relative URL to your attachment:

<pre>$parsed = parse_url( wp_get_attachment_url( $attachment->ID ) );
$url = dirname( $parsed [ 'path' ] ) . '/' . rawurlencode( basename( $parsed[ 'path' ] ) );</pre>
<pre>

If you want a URI for the attachment page, not the attachment file itself, you can use get_attachment_link.

Also refer: wp_insert_attachment, wp_upload_dir, wp_get_attachment_image_src

Source

File: wp-includes/post.php 

function wp_get_attachment_url( $attachment_id = 0 ) {
	global $pagenow;

	$attachment_id = (int) $attachment_id;

	$post = get_post( $attachment_id );

	if ( ! $post ) {
		return false;
	}

	if ( 'attachment' !== $post->post_type ) {
		return false;
	}

	$url = '';
	// Get attached file.
	$file = get_post_meta( $post->ID, '_wp_attached_file', true );
	if ( $file ) {
		// Get upload directory.
		$uploads = wp_get_upload_dir();
		if ( $uploads && false === $uploads['error'] ) {
			// Check that the upload base exists in the file location.
			if ( 0 === strpos( $file, $uploads['basedir'] ) ) {
				// Replace file location with url location.
				$url = str_replace( $uploads['basedir'], $uploads['baseurl'], $file );
			} elseif ( false !== strpos( $file, 'wp-content/uploads' ) ) {
				// Get the directory name relative to the basedir (back compat for pre-2.7 uploads).
				$url = trailingslashit( $uploads['baseurl'] . '/' . _wp_get_attachment_relative_path( $file ) ) . wp_basename( $file );
			} else {
				// It's a newly-uploaded file, therefore $file is relative to the basedir.
				$url = $uploads['baseurl'] . "/$file";
			}
		}
	}

	/*
	 * If any of the above options failed, Fallback on the GUID as used pre-2.7,
	 * not recommended to rely upon this.
	 */
	if ( ! $url ) {
		$url = get_the_guid( $post->ID );
	}

	// On SSL front end, URLs should be HTTPS.
	if ( is_ssl() && ! is_admin() && 'wp-login.php' !== $pagenow ) {
		$url = set_url_scheme( $url );
	}

	/**
	 * Filters the attachment URL.
	 *
	 * @since 2.1.0
	 *
	 * @param string $url           URL for the given attachment.
	 * @param int    $attachment_id Attachment post ID.
	 */
	$url = apply_filters( 'wp_get_attachment_url', $url, $post->ID );

	if ( ! $url ) {
		return false;
	}

	return $url;
}

Uses

Uses Description
wp-includes/functions.php: wp_get_upload_dir()

Retrieves uploads directory information.
wp-includes/media.php: _wp_get_attachment_relative_path()

Get the attachment path relative to the upload directory.
wp-includes/formatting.php: wp_basename()

i18n friendly version of basename()
wp-includes/formatting.php: trailingslashit()

Appends a trailing slash.
wp-includes/load.php: is_admin()

Determines whether the current request is for an administrative interface page.
wp-includes/load.php: is_ssl()

Determines if SSL is used.
wp-includes/link-template.php: set_url_scheme()

Sets the scheme for a URL.
wp-includes/plugin.php: apply_filters()

Calls the callback functions that have been added to a filter hook.
wp-includes/post-template.php: get_the_guid()

Retrieve the Post Global Unique Identifier (guid).
wp-includes/post.php: wp_get_attachment_url

Filters the attachment URL.
wp-includes/post.php: get_post_meta()

Retrieves a post meta field for the given post ID.
wp-includes/post.php: get_post()

Retrieves post data given a post ID or post object.

Used By

Used By Description
wp-admin/includes/template.php: get_media_states()

Retrieves an array of media states from an attachment.
wp-includes/post.php: wp_get_original_image_url()

Retrieve the URL to an original attachment image.
wp-includes/media.php: wp_media_personal_data_exporter()

Finds and exports attachments associated with an email address.
wp-includes/widgets/class-wp-widget-media-audio.php: WP_Widget_Media_Audio::render_media()

Render the media on the frontend.
wp-includes/widgets/class-wp-widget-media-video.php: WP_Widget_Media_Video::render_media()

Render the media on the frontend.
wp-includes/widgets/class-wp-widget-media-image.php: WP_Widget_Media_Image::render_media()

Render the media on the frontend.
wp-includes/class-wp-customize-manager.php: WP_Customize_Manager::import_theme_starter_content()

Import theme starter content into the customized state.
wp-includes/theme.php: get_header_video_url()

Retrieves header video URL for custom header.
wp-includes/rest-api/endpoints/class-wp-rest-attachments-controller.php: WP_REST_Attachments_Controller::prepare_item_for_response()

Prepares a single attachment output for response.
wp-admin/includes/class-wp-site-icon.php: WP_Site_Icon::create_attachment_object()

Creates an attachment ‘object’.
wp-admin/includes/ajax-actions.php: wp_ajax_crop_image()

Ajax handler for cropping an image.
wp-admin/includes/export.php: export_wp()

Generates the WXR export file for download.
wp-admin/includes/image-edit.php: wp_save_image()

Saves image to post, along with enqueued changes in $_REQUEST['history'].
wp-admin/includes/image.php: _load_image_to_edit_path()

Retrieve the path or URL of an attachment’s attached file.
wp-admin/includes/media.php: edit_form_image_editor()

Displays the image and editor in the post editor
wp-admin/includes/media.php: attachment_submitbox_metadata()

Displays non-editable attachment metadata in the publish meta box.
wp-admin/includes/media.php: get_attachment_fields_to_edit()

Retrieves the attachment fields to edit form fields.
wp-admin/includes/media.php: media_sideload_image()

Downloads an image from the specified URL, saves it as an attachment, and optionally attaches it to a post.
wp-admin/includes/media.php: image_link_input_fields()

Retrieve HTML for the Link URL buttons with the default link type as specified.
wp-admin/includes/class-custom-image-header.php: Custom_Image_Header::create_attachment_object()

Create an attachment ‘object’.
wp-admin/includes/class-custom-image-header.php: Custom_Image_Header::ajax_header_crop()

Gets attachment uploaded by Media Manager, crops it, then saves it as a new object. Returns JSON-encoded object details.
wp-admin/includes/class-custom-image-header.php: Custom_Image_Header::step_3()

Display third step of custom header image page.
wp-includes/theme.php: _delete_attachment_theme_mod()

Checks an attachment being deleted to see if it’s a header or background image.
wp-includes/theme.php: get_uploaded_header_images()

Gets the header images uploaded for the current theme.
wp-includes/deprecated.php: get_the_attachment_link()

Retrieve HTML content of attachment image with link.
wp-includes/deprecated.php: get_attachment_icon_src()

Retrieve icon URL and Path.
wp-includes/post-template.php: wp_get_attachment_link()

Retrieve an attachment page link using an image or icon, if possible.
wp-includes/post-template.php: prepend_attachment()

Wrap attachment in paragraph tag before content.
wp-includes/media.php: wp_prepare_attachment_for_js()

Prepares an attachment post object for JS, where it is expected to be JSON-encoded and fit into an Attachment model.
wp-includes/media.php: wp_video_shortcode()

Builds the Video shortcode output.
wp-includes/media.php: wp_playlist_shortcode()

Builds the Playlist shortcode output.
wp-includes/media.php: wp_audio_shortcode()

Builds the Audio shortcode output.
wp-includes/media.php: image_get_intermediate_size()

Retrieves the image’s intermediate size (resized) path, width, and height.
wp-includes/media.php: image_downsize()

Scale an image to fit a particular size (such as ‘thumb’ or ‘medium’).
wp-includes/post.php: wp_get_attachment_thumb_url()

Retrieve URL for an attachment thumbnail.
wp-includes/class-wp-xmlrpc-server.php: wp_xmlrpc_server::_prepare_media_item()

Prepares media item data for return in an XML-RPC object.

Changelog

Version Description
2.1.0 Introduced.

© 2003–2021 WordPress Foundation
Licensed under the GNU GPLv2+ License.
https://developer.wordpress.org/reference/functions/wp_get_attachment_url