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Common Mistakes When Using ACF in WordPress (And How to Avoid Them)

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Introduction

Advanced Custom Fields (ACF) is a powerful WordPress plugin that allows developers and site owners to easily add custom fields to their posts, pages, and custom post types. Whether you're building a custom theme or giving clients more control over their content, ACF can dramatically improve flexibility and efficiency. However, like any tool, it's easy to misuse - especially if you're new to WordPress development or working on complex projects.

In this post, we’ll walk through some of the most common mistakes people make when using ACF and, more importantly, how to avoid them. Whether you're a beginner or an experienced developer, understanding these pitfalls will help you create cleaner, more maintainable, and more performant WordPress websites.

Key ACF Mistakes Developers Make

1. Using the Wrong Function: the_field() vs. get_field()

Mistake:
Using the_field() when you should use get_field() and vice versa.

// Incorrect when you need to store the value
$my_var = the_field('my_custom_field'); // echoes and returns null

// Correct
$my_var = get_field('my_custom_field');

Solution:

• Use get_field() to retrieve the value
• Use the_field() when you want to echo it directly

2. Not Using isset() or empty() Checks Before Outputting

Mistake:
Blindly outputting field values without checking if they exist.

// Risky if the field is not set or empty
<h2><?php the_field('section_title'); ?></h2>

Solution:
Always validate your fields.

$title = get_field('section_title');
if (!empty($title)) {
   echo '<h2>' . esc_html($title) . '</h2>';
}

3. Overusing Repeater Fields for Layout

Mistake:
Using repeater fields where a custom post type or flexible content layout would be more scalable.

Solution:

• Use Repeater fields for structured repeated data like team members
• Use Flexible Content fields or CPTs with a relationship for complex layouts

4. Not Optimizing for Performance

Mistake:
Querying too many ACF fields inside loops. It works fine — but there’s a hidden problem here. Every time you call get_field(), WordPress may ask the database for that custom field. So if you loop through 10 posts, that’s 10 separate database queries!

More posts = more queries = slower website.

while (have_posts()) {
   the_post();
   echo get_field('custom_value'); // Uh-oh! This is slowing you down.
}

Solution:
Instead of asking the database over and over, use get_fields() to get all the custom fields at once for each post:

while (have_posts()) {
   the_post();
   $fields = get_fields(); // One call for all fields
   echo $fields['custom_value']; // No extra queries
}

5. Ignoring Field Group Location Rules

Mistake:
Field groups not appearing because of misconfigured location rules.
Solution:
Double-check rules. Use clear, non-overlapping conditions. If needed, use the "Show this field group if" logic in combination.

6. Not Using Field Keys in PHP Templates

Mistake:
Using field names instead of field keys in places where field names might change.

// Risky if the field is not set or empty
<h2><?php the_field('section_title'); ?></h2>

Solution:
Use the field key (like field_603d2587) in get_field() or update_field() when referencing fields programmatically.

// More reliable for migrations or field name changes
$value = get_field('field_603d2587');

7. Not Escaping Output

Mistake:
Directly printing ACF values without escaping.
Solution:
Use WordPress escaping functions.

$url = get_field('external_link');
echo '<a href="' . esc_url($url) . '">Link</a>';

Conclusion

Advanced Custom Fields is incredibly flexible — but only if used wisely. By following these best practices, you’ll not only improve your site’s performance and maintainability, but also make life easier for both developers and content editors.

Yes, mistakes happen — especially when you're learning or working fast. But with a little awareness and a few smart habits, you can avoid the most common ACF pitfalls and build better, more reliable WordPress sites.

Keep these tips in your toolkit, and you'll save yourself (and your clients) a lot of time and trouble down the line.