Junior Web Developer Interview Questions UK: 8 Real Questions and What Interviewers Want

Applying for a Junior Web Developer job in the UK? Here is what you are likely to be asked. These questions come from our Junior Web Developer question bank of 16 questions, written for UK employers at junior level.

Eight Junior Web Developer interview questions, and what the interviewer is thinking

1. Can you explain the CSS box model and the difference between Flexbox and CSS Grid?

Why they ask: Layout fundamentals are asked in nearly every junior web developer interview.

2. What is the difference between let, const and var in JavaScript, and what is hoisting?

Why they ask: This checks core JavaScript understanding at junior level.

3. What is semantic HTML, and why does it matter for accessibility and SEO?

Why they ask: They want to know you write meaningful markup rather than a soup of divs.

4. How would you make a website responsive, and what does mobile first mean?

Why they ask: Responsive design is fundamental, and nearly all UK web traffic includes mobile.

5. Explain how the DOM works and how you would use JavaScript to respond to a user clicking a button and update the page.

Why they ask: They check you understand how JavaScript interacts with the page.

6. You've been given a bug ticket saying a page looks broken on one customer's phone but fine on yours. What do you do?

Why they ask: They want to see systematic troubleshooting for a junior developer.

7. Tell me about a project where you built a website or web application, and what you learned from it.

Why they ask: Juniors are often judged on portfolio projects and what they learned from building them.

8. Why do you want to be a web developer, and what do you think a junior's first six months should look like?

Why they ask: They want realistic expectations and commitment to learning.

A sample answer to question 1

Can you explain the CSS box model and the difference between Flexbox and CSS Grid?

Every element is a box made of content, padding, border and margin. By default width applies only to the content, so padding and border add to the total size, which is why I usually set box-sizing: border-box to make sizing more predictable. Flexbox is one-dimensional, laying items out along a single row or column, and it's ideal for navigation bars, aligning items within a card or distributing space with justify-content and align-items. Grid is two-dimensional, controlling rows and columns together, so I reach for it for page layouts, galleries and anything where items need to line up in both directions, using grid-template-columns and gap. They work well together: a Grid for the overall page with Flexbox inside components. For responsiveness I combine them with media queries, minmax, auto-fit and relative units. I also use browser dev tools to inspect boxes and debug unexpected spacing or overflow.

Common mistake to avoid: Confusing margin and padding; Saying one replaces the other

Want the rest?

Full model answers, key points and common mistakes for all 16 questions are on the Junior Web Developer interview questions page. The first five are free, no sign-up needed.