How to Get Custom Field Images by ID

Key points:

• WordPress images are stored as attachments with unique IDs, allowing for dynamic retrieval.
• Retrieving by ID enables custom image sizes, attributes, and metadata access without additional database queries.
• Common use cases include working with Advanced Custom Fields (ACF®) fields, featured images, and media library images.
• ACF enhances image management through custom image and gallery fields that work with get_field() to retrieve attachment IDs.
• Performance optimization requires implementing srcset, lazy loading, and proper sizing to ensure images load efficiently across different devices and screen resolutions.

In WordPress, every image you upload is assigned a unique ID – a small, often overlooked detail that unlocks a surprising amount of control.

When you’re building a custom theme, fine-tuning templates, or managing content with tools like Advanced Custom Fields (ACF®), retrieving images by their ID makes for an efficient way to work with media. It allows you to access specific images directly, customize attributes like size and alt text, and ensure consistency across your site.

We’ll walk you through the practical steps of retrieving images by ID in WordPress, offering clear examples and use cases that fit into real-world development workflows.

Core WordPress functions for retrieving images by ID

Here are the key WordPress functions you can use to retrieve images by their ID, depending on what you need:

• wp_get_attachment_image retrieves an image by ID and returns an HTML <img> tag with optional attributes and size specifications.
• wp_get_attachment_url retrieves the URL of an image by its attachment ID for using the image URL directly.
• get_attached_file returns the server file path to the image by attachment ID for file processing or manipulation.
• get_attachment_metadata retrieves metadata for the image, such as dimensions, file type, and other properties.
• get_the_post_thumbnail retrieves the featured image (post thumbnail) for a given post or page by post ID, with options for size and attributes.
• get_post_thumbnail_id retrieves the ID of the featured image for a specific post for further image manipulation.
• get_attachment_image_src retrieves the URL, width, and height of an image by its ID for responsive layouts.
• get_image_tag, similar to wp_get_attachment_image, returns the image tag directly for custom use.
• get_post_meta retrieves the image metadata stored as post meta, providing additional data about the image file.

How to find an image ID in WordPress

There are different methods you can use to find an image’s ID:

• Check the Media Library and look at the image’s URL in your browser to find the ID at the end of the link.
• Call get_post_thumbnail_id($post_id) to fetch the ID of a featured image assigned to a specific post or page.
• Use get_field('field_name') in ACF to pull the image ID from a custom image field, as long as it’s configured to return the ID.
• Run attachment_url_to_postid($image_url) to convert a stored image URL into its corresponding attachment ID.
• Use get_attached_file($attachment_id) to retrieve the full server path of an image based on its ID.

Methods for retrieving WordPress images by ID

Once you have the image ID, WordPress offers several built-in functions to retrieve the image in different formats. These methods let you access everything from the image URL to a full HTML tag, depending on your needs.

Retrieving general images

When working with general images – those not tied to featured images or specific fields – you can use several core functions to retrieve them by their attachment ID:

• Use wp_get_attachment_image($attachment_id, $size, $icon, $attr) to get a full <img> tag with control over size, icon display, and additional HTML attributes. Set $icon to true if you want to return a small icon version of the image.
• Call wp_get_attachment_url($attachment_id) to retrieve the direct URL of an image for use in custom markup or inline styles.
• Use get_attached_file($attachment_id) to get the absolute server path of an image, useful when handling file operations or generating thumbnails manually.
• Call get_attachment_metadata($attachment_id) to access detailed information about the image, including dimensions, file size, and MIME type.
• Use get_attachment_image_src($attachment_id, $size) to return an array with the image URL, width, and height – ideal for responsive image handling.
• Run get_image_tag($attachment_id, $size, $icon, $attr) when you want a complete image tag quickly, especially in custom templates or markup-heavy areas.

Retrieving featured images and thumbnails

Featured images in WordPress – also known as post thumbnails – are commonly used for blog posts, pages, and custom post types. These functions let you retrieve or display them directly using the post ID:

• Use get_post_thumbnail_id($post_id) to get the attachment ID of a post’s featured image for use in other image functions.
• Call get_post_meta($post_id, '_thumbnail_id', true) to access the featured image ID directly from post meta, which can be useful in custom queries.
• Use get_the_post_thumbnail($post_id, $size, $attr) to retrieve the full HTML <img> tag for a post’s featured image, with control over size and attributes.
• Call the_post_thumbnail($size, $attr) inside the loop to immediately display the featured image for the current post.

Retrieving custom field images with ACF

ACF expands what’s possible with images in WordPress by letting you collect, manage, and retrieve them through custom fields tailored to your content.

Using ACF’s get_field() function, developers can pull image data exactly where and how they need it – without wrestling with extra plugins or convoluted logic.

The team behind ACF sees this flexibility in action every day. As Liam Giddy, Senior Staff Engineer, put it:

“Managing and retrieving images using ACF opens up endless possibilities. You can tailor your design, optimize your layout, and deliver a fresh experience every time.”

ACF bridges the gap between WordPress’s basic image support and the real-world needs of modern sites, giving developers a flexible and intuitive way to handle images in even the most complex layouts.

This becomes especially useful in practical scenarios, like:

• Dynamically retrieving large, featured images for homepage sliders or hero sections.
• Fetching and displaying profile images for user accounts or team member bio pages.
• Retrieving and displaying personalized images, like user-uploaded images in a content-rich website or app.

Retrieving a single image field

The ACF image field is one of the most commonly used field types – 58.33% of developers say they always include it in their projects.

You can set it to return the image ID when you’re creating it:

Once that’s done, you can easily retrieve and display the image using standard functions:

• Call get_field('my_image_field') to retrieve the image ID stored in the ACF field.
• Use wp_get_attachment_url($image_id) to get the direct URL of the image if you need it for custom markup or inline styles.
• Call wp_get_attachment_image($image_id, 'full') to output the image as a complete <img> tag, ready to display in your template.

Retrieving a gallery field

The ACF gallery field, available in ACF PRO, returns an array of images that can be looped through and displayed individually.

Once you’ve retrieved the field, you can check for images and output each one using WordPress image functions:

• Use get_field('your_gallery_field') to get the array of images from the gallery field.
• Check if the array is not empty, then loop through each image and call wp_get_attachment_image($image['ID'], 'medium') to display each image in medium size with a full <img> tag.

Tips for optimizing WordPress image retrieval

To make the most of image retrieval by ID in WordPress, you need to optimize how those images are delivered and rendered on the page. Here are several practical tips to improve performance, responsiveness, and user experience:

• Use srcset to provide multiple versions of an image for different screen resolutions, letting the browser choose the best one for the device:

<img src="image.jpg" srcset="image.jpg 1x, [email protected] 2x"/>

• Specify sizes to guide the browser on the intended display width, improving the efficiency of image selection from the srcset:

<img src="image.jpg" sizes="(max-width: 600px) 100vw, 600px"/>

• Add loading="lazy" to defer image loading until the image is near the viewport, which reduces initial page load time.
• Apply fetchpriority="high" to critical, above-the-fold images to ensure they load as early as possible for faster visual rendering.
• Enable decoding="async" to let the browser decode images asynchronously, preventing layout blocking during page load.
• Use the Picturefill library as a polyfill for older browsers that do not support srcset or sizes, ensuring responsive image support across all environments.

Simplify WordPress image management with ACF

WordPress gives developers everything they need to retrieve and display images by ID, using functions like wp_get_attachment_image() and get_the_post_thumbnail() to place images exactly where they belong.

ACF raises the bar, offering a structured, intuitive way to manage images across your site. With get_field(), you can pull single images, full galleries, and anything in between – all tied neatly to the content that matters.

For developers juggling dynamic layouts and content-heavy sites, ACF is transformative.

Explore ACF PRO for powerful extras like gallery fields and repeaters that make your work faster, smarter, and a lot more satisfying.