WordPress Developer Interview Questions UK: 8 Real Questions and What Interviewers Want

Applying for a WordPress Developer job in the UK? Here is what you are likely to be asked. These questions come from our WordPress Developer question bank of 12 questions, written for UK employers at mid-level level.

Eight WordPress Developer interview questions, and what the interviewer is thinking

1. Explain the difference between actions and filters in WordPress, and give an example of each.

Why they ask: Hooks are the foundation of WordPress development, so this is almost always asked.

2. How would you build a custom theme or a child theme, and when would you use a block theme versus a classic theme?

Why they ask: Theme architecture is a core WordPress skill, particularly with the move to full site editing.

3. How do you secure a WordPress site?

Why they ask: WordPress sites are common attack targets, so security knowledge is essential.

4. How do you optimise the performance of a slow WordPress site?

Why they ask: Performance affects SEO and conversions, and clients expect developers to fix it.

5. Tell me about a time you significantly improved the speed or security of an existing WordPress site.

Why they ask: They want evidence of measurable improvements on real client sites.

6. How would you build a custom plugin, and what best practices do you follow?

Why they ask: They want to see that you can write maintainable, safe PHP for WordPress.

7. A client's WordPress site displays a white screen after a plugin update. What do you do?

Why they ask: This is a common real-world incident and tests calm troubleshooting.

8. Why do you want to work as a WordPress developer, and what makes a great one?

Why they ask: They check motivation and understanding of the commercial side of the role.

A sample answer to question 1

Explain the difference between actions and filters in WordPress, and give an example of each.

Both are hooks that let me change WordPress behaviour without editing core files. An action lets me run my own code at a specific point in execution, and it does not return anything. For example, I might use add_action with wp_enqueue_scripts to load a stylesheet and script on the front end, or with save_post to trigger something when a post is saved. A filter lets me modify data as it passes through WordPress, and I must return the value. For instance, I can use add_filter on the_content to append a call-to-action after each post, or on excerpt_length to change the number of words. Priority and accepted arguments control the order and the information passed. I also create my own hooks with do_action and apply_filters in plugins, so that other developers can extend my code. I always sanitise and escape within the callbacks, and I remove hooks with remove_action when overriding third-party behaviour.

Common mistake to avoid: Not returning a value from a filter; editing core or parent theme files

Want the rest?

Full model answers, key points and common mistakes for all 12 questions are on the WordPress Developer interview questions page. The first five are free, no sign-up needed.