Optimising Core Web Vitals on SPAs
Single-page applications present some unique challenges for measuring and optimising core web vitals, here we review the key optimisations you should be making for your SPA
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Hi! I'm Simon, a freelance web performance consultant. I help my clients to deliver fast and inclusive web user experiences.
I write about web performance and speak about it at conferences. I also help to run the London Web Performance Group. I provide consultancy to clients of all sizes to help improve their web performance and user experience - find out more.
All Blog Posts
Fixing empty responses from Cloudflare Workers Sites
A quick fix for empty response bodies on Cloudflare Workers Sites
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Survivorship Bias in Web Performance
Why your analytics shows your site as faster than it is, and why FCP is a key metric to optimise for.
The value of an independent web performance consultant
If you're wondering if you need an independent web performance consultant, this is why I think you do!
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Caching Header Best Practices
Caching headers are surprisingly complex and often misconfigured. Here we look at some key cache scenarios and recommend the ideal headers to set.
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Fast and Responsive Hero Videos for Great UX
Responsive landing page hero videos are increasingly popular, here we show how to make them as fast as possible.
An Inclusive Web is Fast by Default
Web performance is critical to inclusive design - users on low-end devices or with poor connectivity are excluded from large and slow applications
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Slow site speed is still the biggest cause of web stress
It's something we've all felt before: the stress and anger induced when trying to use a frustratingly slow website or app. It's really hard to quantify this feeling though, and even harder to track it in your users.
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Everything we know about Core Web Vitals and SEO
There has been a lot of uncertainty and confusion since Google announced the Page Experience Update in 2020. In this post we will summarise everything we know about the update and the potential SEO impact
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How to avoid layout shifts caused by web fonts
One of the biggest causes of layout shifts for my clients is late-loading web fonts, let's look at how to optimise them!
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Optimistic UI Patterns for Improved Perceived Performance
Speed is in the eye of the beholder, it is a perception of how fast an experience feels. Optimistic UI patterns can significantly improve perceived performance for relatively little effort.
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Alternatives to Spinners on the Web
Animated spinners are so 1999, there are some obvious and less-obvious alternatives to improve user experience.
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Web Performance Predictions for 2021
2020 was a wild ride. Here are five key things to watch in the world of web performance in 2021!
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The Impact of Let's Encrypt Changes on Android Users
Let's Encrypt will use its own root certificate in 2021, this may block access to 12% of Android users globally.
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The Performance Cost of EV Certificates
Extended Validation certificates are expensive and degrade performance. Move to an OV certificate if you can!
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Getting Fast and Staying There
Getting fast is difficult, staying fast even more so. How do successful companies ensure that their site speed stays at peak?
What is the best page speed metric?
Out of the hundreds of available performance metrics, which ones make sense for you?
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Four Charts That Prove the Value of Site Speed
Site speed is critical to user experience and online success, here are four charts which prove the value!
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How to Improve Core Web Vitals
Core Web Vitals are three new performance metrics which will soon impact SEO ranking. Learn how to measure and improve them to maximise user experience!
The Psychology of Speed
We intuitively know that faster is better, but what's the psychology and physiology behind it?
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Giving Great (Remote) Software Demos
Giving great software demos is both science and art. Here are some tips on making the most out of every demo opportunity, even when you're stuck at home!
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Who Opts-in to Save-data?
A primer on save-data, what it means for your users and what it means for you.
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Measuring Performance behind consent popups
Opting in to cookies can load multiple megabytes of additional content. Here are tips on how to measure web performance both with and without cookie consent.
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When Network is Faster than Cache
We assume that browser caches are near-instantaneous, but data shows that retrieving an object from cache can take hundreds of milliseconds!
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Is it time for a Web Performance rebrand?
Web Performance is a niche term in a broad market, should we widen our appeal to reach more people?
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Collecting SmartThings data in InfluxDB on Raspberry Pi
How to collect data from your Home Automation system into a local timeseries database.
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Collecting SpeedTest results in Influx on Raspberry Pi
How to set up regular SpeedTest reports into a local InfluxDB on a Raspberry Pi
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Reporting Raspberry Pi System Metrics to InfluxDB
How to set up regular system stat reports from a Raspberry Pi into a local InfluxDB
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Installing InfluxDB & Grafana on Raspberry Pi
I recently treated myself to a RaspberryPi 4 Model B to use as a(nother) home server. This is a brief guide on getting InfluxDB and Grafana set up to store and graph timeseries data.
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HTTP Headers for fast & secure static sites
An introduction to key HTTP response headers for speed and security, with implementation guides for Netlify & CloudFlare
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Six Web Performance Technologies to Watch in 2020
Don't bet on 5G and HTTP/3 to make things faster, there are six technologies that I believe will have a bigger impact on web performance in 2020.
Deep dive into third-party performance
A deep-dive into the impact of third-party tags on web performance.
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Native image lazy loading has landed in Chrome, maybe don't use it
Native lazy loading for iframes and images landed in Chrome 76, but don't go ripping out your existing lazy loading strategy just yet.
WebPageTest Private - 'no successful results'
A potential quick fix for "The test completed but there were no successful results." in WebPageTest private instances.
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Why Site Speed is Critical for Online Publishers
Site speed is a critical factor in the success of an online publishing business, whether revenue is driven by adverts or subscriptions. This post demonstrates the relationship between speed and publishing revenue, and suggests some quick wins to improve both!
Lead Developer Conference (London) - Day 1!
Lead Developer is a conference for senior and lead software engineers. These are my raw notes from day one.
Delta V Conference - Day 2!
Delta V Conference is a new two-day, single-track web performance conference in London, hosted by me, Perry Dyball and Jo Franchetti. Here's my raw notes from the fantastic content from our lovely speakers on day two.
Delta V Conference - Day 1!
Delta V Conference is a new two-day, single-track web performance conference in London, hosted by me, Perry Dyball and Jo Franchetti. Here's my raw notes from the fantastic content from our lovely speakers on day one.
Third-Party Content - the weak link?
The Resource Timing API allows site owners to measure how third-parties perform for every single pageview. Combining this data with business intelligence provides new insight to the impact of third-party providers on business performance.
Twitter Lite isn't as good as the app, and that's okay
Twitter's Progressive Web App is finally out of testing, and it's not as good as the native app. Missing push notifications, wonky images, small text boxes, lack of sharing intents and confusing pull-to-update behaviour all highlight the challenge of building a PWA. The fact that Twitter is on-board with PWAs is a great step towards better web experiences...
Your Analytics Lies to You
You can't rely on your web analytics for performance data and it's understating bounce rate and traffic numbers from old devices.
How to Optimise CSS Image Sprites
Optimising sprites might be more important than you think, and easier than you expect!
Three WebPerf Takeaways from Velocity Europe
Velocity Amsterdam has just come to a close. Here are the three key things that I am taking away from the two days of sessions.
Velocity NY 2016 - Wrap-up
Velocity New York seems like a distant memory now, especially with Velocity Europe around the corner. With that said, I have copious notes from the two day conference which I have summarised here. There were a lot of nuggets of wisdom which I’ll try to organise into a logical order.
Blocking requests in webpagetest? Don't use Chrome.
We know that third-party content can harm the user experience on a website. Measuring that impact can be tricky.
How fast is fast enough?
Do you know when your website’s speed starts to impact your customers’ behaviour?
Getting Reliable Visual Performance Metrics
Tips to get more reliable & consistent visual metrics from WebPageTest
Render Conf 2016
Render Conference - previously known as jQuery UK - was held in Oxford last week. It's a front-end conference for front-end people, which makes me a bit of an outsider. Performance is not the focus of Render Conference. Render is an opportunity for me to hone up my front-end skills and get an idea of what front-end developers are up against and the latest...
Prioritising Site Speed Recommendations
Sometimes prioritising recommendations is more important than making them.
Velocity Europe 2015 - The Good Ones!
This post is a review and summary of the talks at Velocity Europe that I attended. I've summarised each talk and given links to the slides, videos and ratings. A previous post contains the talks that got a five star review from me. Less than a five star review is not a bad thing, though. Five stars means exceptional, while three stars means the talk had s...
Velocity Europe 2015 - My Allstars
This post is a review and summary of the talks at Velocity Europe that got a 5 star review from me. I've summarised each talk and given links to the slides, videos and ratings. A further post contains the talks that didn't quite get a five star review from me.
Measuring Webpage Jank
Webpage jank can harm the user experience, here's an easy way to measure it on your pages
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Be Mindful With Modernizr
Modernizr might be making your site slow, especially on mobiles
The Future of Web Performance - Part 1
Web performance is critically important, how will upcoming technologies change the way we manage it?
Questions to Ask Your Third-Parties
We need rules to keep third-party Javascript in check.
Manage Third-party Risk Using a Content Security Policy
A feature to prevent cross-site-scripting may make it easier to police third-party javascript.
Using a Web Performance Heatmap to Assess Page Performance
I've made a Heatmap to visualise when each element loads on a page.
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How to Find the Third-Parties on Your Site
Third-party means not you or me, but them.
Web Performance Optimisation Basics
Website performance is critical to user experience. We need rules to make it easier.