HTML Interview Questions: SEO, Performance and Tooling

Why a developer gets asked these

SEO and performance questions in a front end interview are not testing marketing knowledge. They are testing whether you understand the markup consequences: which tag affects what, and what a wrong one costs.

Questions only.

How search works

1. Describe the stages between publishing a page and it appearing in search results.
2. What is the difference between crawling and indexing?
3. A page is blocked in robots.txt and carries a noindex tag. What actually happens?
4. How would you correctly remove a page from search results?
5. What is an orphan page and why does it matter?
6. Does Google execute JavaScript? What is the practical consequence for a client rendered page?
7. What is crawl budget and when does it become a real constraint?

On page markup

8. What does the title element affect? Name four things.
9. Is the meta description a ranking factor? What does it affect?
10. How long should a title and a description be, and why is the title limit not a character count?
11. Why should there be one h1 per page, and what should it contain?
12. What does a canonical tag do? Why must it be absolute?
13. Give three ways the same page ends up at several URLs.
14. Should paginated pages canonicalise to page one? Explain.
15. Why does the keywords meta tag not matter?
16. What is structured data and what does it actually change?
17. What are the rules Google enforces on structured data?
18. What does hreflang do, and what makes a set of them invalid?

Performance

19. Name the three Core Web Vitals, what each measures and the threshold for each.
20. Give three markup changes that improve Largest Contentful Paint.
21. What causes Cumulative Layout Shift and how do you fix each cause?
22. Explain the difference between a blocking script, defer and async.
23. Where should a stylesheet be linked and why?
24. What is preload for, and what is the cost of getting it wrong?
25. What does mobile first indexing mean for content hidden on small screens?

Tooling

26. How do you debug a page where the CSS is not applying? Walk through your process.
27. Why is the Elements panel more reliable than view source?
28. How would you find out why a form field is not reaching the server?
29. What does the HTML validator catch that a browser does not tell you about?
30. How would you verify that a responsive image is serving the right file?

The follow ups

A question you should ask them

Interviews go both ways. Asking how do you currently measure accessibility and performance, and is it in CI? tells you a great deal about how the team works - and signals that you think about it as a continuous thing rather than a launch task.

Practice

1. Answer all thirty out loud.
2. Run Lighthouse on a page you built and be ready to discuss the results.
3. Prepare one specific story about a performance or SEO problem you diagnosed.
4. Practise the debugging walkthrough in question 26 while actually doing it.