Sentinel: Your Web-Performance Watchman

About Me

Hi there, I’m Harry Roberts. I am an independent Consultant Web Performance Engineer from Leeds, UK. I help some of the world’s largest and most respected organisations deliver faster and more reliable experiences to their customers. I am an invited Google Developer Expert, a Cloudinary Media Developer Expert, an award-winning developer, an international speaker, and co-chair of the inimitable, the web performance conference for professionals.

Workshopping at Digital Labin, 2022. Photograph by Ivica Džambo.

With over 15 years of professional experience, and a decade working as an independent consultant, I have been trusted by the likes of the United Nations, Google, the BBC, General Electric, and many more. Through combinations of workshops, training, audits, development, and consultancy, I have helped my clients to build and scale resilient, performant front-ends for a variety of applications.

There is a short list of people I whole-heartedly recommend for detailed performance work and Harry is right there at the top.

Tim Kadlec

Internationally recognised as a leading expert in CSS architecture and front-end performance, it is my job to help companies accomplish the return on investment that web performance efforts can bring, whether that is increasing conversions, improving engagement, or growing revenues. I thrive on being a business-focused engineer, equally comfortable in front of C-level executives as I am in front of a room full of developers.

Most importantly, I am available for hire. My work spans many industries, countries, and formats. From troubleshooting and assessing existing performance issues, to training engineers to debug and avoid these common pitfalls in future; from advising and consulting with teams to get a handle on web performance issues, to everything else in between. If you need a faster website, we’ll get you a faster website.

If you think I can help you—and I probably can—say hello: I enjoy working with companies of all shapes, sizes, locations, problems, needs, and budgets. I’m professional, but I’m very laid back—drop me a line, and we can see what fits.


Hire me.


CSS Wizardry makes use of many great tools and services; tools and services that make my life as a developer much, much simpler.

CSS Wizardry is built on Jekyll, an open source static site generator. This is hosted using GitHub Pages and served via Cloudflare.

The CSS is written in Sass, and built on top of inuitcss. inuitcss is a free, open-source, Sass-based, OOCSS framework with a strong focus on performance, scalability, and a small footprint. This is then built into ITCSS, a CSS architecture of mine which is designed to aid the growth and maintainability of CSS projects.

Your system font is used to give a familiar feel and to help improve performance. Responsive testing was made possible by Finch, an incredible tool for exposing local dev sites to the open internet. SpeedCurve and Treo help keep CSS Wizardry fast.

The photograph used on the homepage’s masthead is of me speaking at DotYork, and was taken by Jim Poyner.

CSS Wizardry’s roadmap and task list are viewable on a public Trello board, and all of the code that powers it can be found on GitHub. Feel free to take a look round, but please don’t steal anything.

I chose the name CSS Wizardry when I was 17 years old. It’s a decision that I’m having to live with…

Interviews and Podcasts

  1. Podcast

    : ScriptCast
  2. Podcast

    : Non Breaking Space Show
  3. Podcast

    : Hacking UI
  4. AMA

    : Hashnode
  5. Podcast

    : The Web Platform Podcast
  6. Interview

    : Honeypot
  7. Podcast

    : – Travel Tools
  8. Interview

    : CSSConf Australia
  9. Podcast

    : Being Freelance – CSS Wizard Harry Roberts – Developing Consultant Magic
  10. Podcast

    : Unfinished Business – Two old farts looking at their calendars
  11. Interview

    : ColourSpaces
  12. Video interview

    : DaFED
  13. Interview

    : PSDtoWP – 3 beloved front-end development tools
  14. Podcast

    : Unfinished Business – A cage full of hungry dogs
  15. Podcast

    : CDNify – An Interview with CSS Expert Harry Roberts
  16. Interview

    : Insurance By Jack – How To Get Started With Public Speaking
  17. Video interview

    : FOWD – 10 Minutes ’til the Future – Live from FOWD edition
  18. Interview

    : Workspiration
  19. Interview

    : Sitepoint – CSS Framework Fortunes and Failures with Harry Roberts
  20. Interview

    : Responsive Design Weekly – Responsive Interview with Harry Roberts
  21. Interview

    : net mag – Harry Roberts on big CSS, working for Sky, and being a home bird
  22. Interview

    : Alex Carpenter — Harry Roberts of CSS Wizardry
  23. Podcast

    : Web Payload – Why not to use IDS? The tipping point, inuitcss, and frameworks
  24. Podcast

    : Unfinished Business – Almost as controversial as putting the milk in first
  25. Interview

    : Steer – An interview with Harry Roberts
  26. Interview

    : Web Courses Bangkok – An Interview With Harry Roberts – Front-end Architect and Speaker
  27. Interview

    : net mag – Use shame.css to house hacks
  28. Podcast

    : Up Front Podcast – CSS with Harry Roberts
  29. Podcast

    : Shop Talk Show
  30. Interview

    : Martin Wolf – Interview with CSS wizard Harry Roberts
  31. Podcast

    : Young Guns Show – Scalable CSS with Harry Roberts
  32. Interview

    : Nu Blue – Off to see the Wizard

Hi there, I’m Harry Roberts. I am an award-winning Consultant Web Performance Engineer, designer, developer, writer, and speaker from the UK. I write, Tweet, speak, and share code about measuring and improving site-speed. You should hire me.

You can now find me on Mastodon.

Suffering? Fix It Fast!


  • inuitcss
  • ITCSS – coming soon…
  • CSS Guidelines

Next Appearance

  • Talk & Workshop

    WebExpo: Prague (Czech Republic), May 2024


I am available for hire to consult, advise, and develop with passionate product teams across the globe.

I specialise in large, product-based projects where performance, scalability, and maintainability are paramount.