How to Add a Custom Field in WordPress

To add a custom field with the built-in panel, enable Custom fields in the editor's Preferences, then save a name and a value on the post. WordPress stores the pair as post meta; the panel is hidden in the block editor until you switch it on.

1. Edit the post. Open the options menu in the top bar and choose Preferences.
2. Open the Panels section and enable Custom fields. The editor reloads.
3. Under the content, choose Enter new. Type a key such as source_url and a value. Click Add Custom Field.
4. Update the post. The pair is saved even though the public page does not show it yet.

To show a custom field, fetch it with get_post_meta for the current post id, then escape it before printing. Escape as text with esc_html, as a link with esc_url, and as markup with wp_kses_post, so a stored value can never inject script into the page.

$source = get_post_meta( get_the_ID(), 'source_url', true );
if ( $source ) {
    echo '<p>Source: <a href="' . esc_url( $source ) . '">link</a></p>';
}

Put that in a child-theme template or a small site-specific plugin, and test on a copy: a syntax error in a template file returns a white screen, which WP_DEBUG will explain.

In a block theme you can skip PHP entirely with the Block Bindings API (WordPress 6.5 and later). Register the key with show_in_rest, then bind a Paragraph, Heading, Image or Button block to it in the code editor (see the Gutenberg blocks guide). Keys that start with an underscore are protected and cannot be bound.

register_meta( 'post', 'source_url', array(
    'show_in_rest' => true,
    'single'       => true,
    'type'         => 'string',
) );

<!-- wp:paragraph {"metadata":{"bindings":{"content":{"source":"core/post-meta","args":{"key":"source_url"}}}}} -->
<p>Fallback text</p>
<!-- /wp:paragraph -->

Choose the built-in panel for one or two text notes, Advanced Custom Fields for typed field groups with location rules, and Meta Box when the project needs many field types without a page-builder dependency. All three save to the same postmeta table.

Do not drive the same key from the built-in panel and a plugin at once. Pick one writer, or the value is saved twice under two names and the template reads whichever one it was told to read.

To check a custom field saved, reopen the post and confirm the value is still in the panel; if it vanished, the save handler returned early or the key was misspelled. Then load the public page in a private window, because a cached copy hides fresh output.

When the panel holds a value but the page prints nothing, check the template runs for that post type and that the key in the code matches the key in the database exactly. A quick var_dump of get_post_meta for the post id shows what WordPress actually stored.

None of this depends on the hosting account: the field and the code travel with the site. On WebJi® WordPress hosting you can inspect postmeta directly in phpMyAdmin from the hosting panel.