Sentinel: Your Web-Performance Watchman

Thank You!

You made it! Welcome aboard.

From now on, you can expect infrequent updates about

  • upcoming conferences,
  • discounts for events,
  • insights and findings,
  • interesting resources,
  • and exclusive content.

Here are all of the previous newsletters that you may have missed:

  1. Issue #0001:
  2. Issue #0002:
  3. Issue #0003:
  4. Issue #0004:
  5. Issue #0005:

Right now though, here’s a screencast showing you how to troubleshoot rendering performance:

Head back to the homepage

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.