How Fast Is Fast Enough?

It sounds like a simple question, but if you've been working in performance long enough, you know the answer is far from straightforward. In our Day 1 keynote, Tammy will ask questions — ranging from neuroscience to business metrics — that will get you thinking about how you create, measure, and report your performance goals.

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Tammy Everts

Embrace

Tammy Everts is chief experience officer at SpeedCurve, where she helps companies understand how visitors use their websites, and a co-chair of performance.now(). Tammy has spent the past two decades studying how people use the web. Since 2009, she’s focused on the intersection between web performance, user experience, and business metrics. Her book, Time Is Money: The Business Value of Web Performance from O’Reilly, is a distillation of much of this research. She also cocurates (with Tim Kadlec) WPO Stats, a collection of performance case studies.

How to Think Like a Performance Engineer

As awareness and tooling around site speed have been improving at a very exciting rate, has performance testing actually become any easier? Any more straightforward? As someone who spends every day auditing client projects, I think areas of confusion have actually increased in many places. Which tools should we be using? Can we trust them? How do we run tests that serve as realistic and actionable predictors? And how do we know when we’ve won?

In this talk, we’ll look at highly practical tools and workflows to ensure that every test we run has a purpose and gives us data we can truly leverage. By the end, we will all have a shared idea of what effective performance testing looks like, as well as customised and fine-tuned tooling to ensure replicable and predictable tests.

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Harry Roberts

Consultant Web Performance Engineer

Harry Roberts is an independent Consultant Web Performance Engineer from the UK. He helps some of the world’s largest and most respected organisations find and fix their site-speed issues.

He is both a Google- and a Cloudinary Media-Developer Expert, and has consulted for clients from the United Nations to the BBC, General Electric to the Financial Times, and a whole host more. He is also co-chair of performance.now(), the web performance conference for professionals.

When not doing client work, he writes, teaches, and speaks about the entire gamut of front-end performance. When not doing work at all, he’s probably out on his bike.

Accessibility and Performance

What if performance meant more than speed – what if it included how intuitively and equitably people can interact with your website? This session takes a practical look at how designing for accessibility contributes to more responsive, usable experiences, especially for disabled users. We’ll explore how access patterns across devices, locales, and input methods influence perceived responsiveness, and why subtle choices — like how content loads or which elements receive focus — can have outsized effects on usability.

We’ll look at tangible ways to measure your interfaces beyond load speed — like how long it takes assistive tech to surface meaningful content, or how much effort it takes for someone to complete a task. Along the way, we’ll talk about design and engineering strategies, legal context in Europe, and the satisfaction of building digital products and services that genuinely work better for more people.

If you care about impact, and you're curious how accessibility efforts intersect with web performance, join me. You might leave with a few new metrics — and a fresh sense of purpose.

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Marcy Sutton Todd

Khan Academy

Marcy Sutton Todd is a Senior Engineer on the Frontend Infrastructure team at Khan Academy, where she works on design systems, accessibility, and test automation. Throughout her career, Marcy has shared what she’s learned about web accessibility to show how we can all contribute easy wins and lasting contributions. As an independent web developer, Marcy created the website Testing Accessibility to encourage designers and developers to test their own work. She has also grown her impact by working on numerous accessibility testing tools, website frameworks, and by leading communities. In her free time, Marcy enjoys riding bikes with her family, lifting weights, hiking and van exploring, eating spicy food, and cooking.

Big Data, Zero JS: Cross-Browser Virtual scrolling

CSS content-visibility is a powerful tool that bypasses unnecessary rendering for offscreen content, drastically improving load times and responsiveness. In this talk, I'll demonstrate meticulously crafted benchmarks, practical techniques to harness this property in real-world, content-rich environments, and a couple of case studies highlighting its potential in the fiend.

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Michael Hladky

CEO, PushBased

Michael Hladky is a Google Developer Expert (GDE), Microsoft MVP, and Nx Champion with a deep focus on web performance and scalability. As CEO of PushBased, he helps teams and organizations design streamlined architectures and build blazing-fast applications. With years of experience as a trainer and consultant, Michael is passionate about empowering developers through practical expertise and high-impact solutions. A dedicated community contributor, he speaks at international conferences, leads workshops, and organizes events to support and inspire fellow developers.

Fast, green, responsible

Performance work has always been about speed. But speed is only part of the story. Every byte shipped carries a carbon cost, and decisions made in design and development ripple far beyond milliseconds. This session explores how web performance and sustainability are deeply connected: why faster sites are greener sites, and how minimal, efficient design becomes a responsibility that can no longer be ignored.

Insights from the W3C Sustainable Web Guidelines will be presented alongside practical principles for building with both users and the planet in mind. Emerging ideas such as carbon aware websites, which adapt in real time to the carbon intensity of the grid, will be introduced as a way forward for bridging the gap between performance culture and sustainability.

The result is a vision of web performance that is not only fast, but also green and responsible, with concrete steps available today.

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Ines Akrap

Green Software Champion

Ines Akrap is a Frontend Software Engineer passionate about optimizing websites to be fast, sustainable, and provide the best user experience for every user. She works in Storyblok as Solutions Engineer.

She is a Web Performance Google Developer Expert and Green Software Champion. She co-chairs W3C Sustainable Web Interest Group that is actively working on new version of Web Sustainability Guidelines (WSG). She enjoys sharing her knowledge with others through talks, podcasts, workshops, and courses.

When not knee-deep in performance budgets, estimating the CO2 emissions of JS files, or explaining what is “headless”, Ines is busy navigating life as a mother of two—balancing toddler negotiations with newborn care, and embracing the chaos and joy of raising small humans. All she wants for Christmas is one good night’s sleep.

Modern Performance Workflows

This talk will cover recent browser DevTools features, and also explore how AI assistance in DevTools can speed up your debugging workflow with practical examples.

You'll learn about modern automated workflows using coding agents that work with the DevTools protocol, browser automation, and Model Context Protocol, and will explore ideas on how these tools can be integrated into your development process and CI/CD pipelines for automated performance testing.

By the end, you'll pick up modern automated workflows to help you catch performance issues before they reach production.

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Umar Hansa

Independent developer

Umar is a web developer, public speaker and content creator based in London. Umar has a focus on writing tips, tutorials and documentation for the modern web platform. One of the projects he plans to explore and share with the community is using modern tools and technologies for a better development and debugging workflow.

Making Performance Allies

Web performance data often serves as a proxy for key business metrics. Framing this data in ways that resonate with business stakeholders can help build alliances and drive advocacy for web performance initiatives across the organization. This talk will offer practical tips on presenting engineering data as a competitive advantage, a revenue driver, and a tool for enhancing user experience to help make performance optimization a strategic priority.

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Ethan Gardner

Flexion/Independent

Ethan Gardner is a full-stack engineer and educator with expertise in front-end development, focused on creating high-performance web applications, identifying process efficiencies, and elevating development teams through mentorship and teaching. He has worked as an engineer and technical leader in industries such as media, advertising, hospitality, and the public sector. He currently works at Flexion and is also developing courses to help engineers level-up their skills.

Tim Kadlec

Cloudflare

Tim Kadlec is a performance consultant and trainer focused on building a web everyone can use. He is the author of High Performance Images (O’Reilly, 2016) and Implementing Responsive Design: Building sites for an anywhere, everywhere web (New Riders, 2012), and was a contributing author for Smashing Book #4: New Perspectives on Web Design (Smashing Magazine, 2013), and the Web Performance Daybook Volume 2 (O’Reilly, 2012). He writes about all things web at timkadlec.com. You can find him sharing his thoughts in a briefer format on Twitter at @tkadlec.

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LoAF

Over time the web has become more reliant on JavaScript. Some believe JavaScript is the only way to build the modern web and dismiss the performance concerns, while others hold opposing views.

Wouldn't it be great if we had data on how scripts actually perform in our visitor's browsers – when they delay loading, cause jankiness and slowdown interactions, and perhaps more importantly which scripts are responsible?

After all, if we can't measure it, how can we improve it?

The Long Tasks API was a first attempt at providing this data but it couldn't answer the question of why the main thread was busy.

The Long Animation Frames (LoAF) API aims to overcome the weaknesses by also providing details on what Main Thread activity caused the long frame, if possible.

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Andy Davies

SpeedCurve

Andy is a Web Performance Consultant at SpeedCurve, where he helps organisations to measure and improve the speed of their sites.

He stumbled into web performance in 2008 while launching an online education service and quickly ran into the challenge of delivering rich content to schools over congested networks.

Since 2012 he's focused on web performance full time and has worked with a wide range of organisations from international retailers and news publishers to financial services and FMCG brands.

Measuring Interactions and Navigations

LCP and INP measure page loading and responsiveness– but same-document Soft-Navigations have always blurred these distinctions. Now, it's finally possible to measure these! Come learn about some exciting new Performance APIs, how they work, and what might come next…

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Michal Mocny

Google Chrome team

Michal Mocny has been part of the Canadian Google Chrome team for 14 years, spending the last 5+ years focused on Speed Metrics. He was the Tech Lead for the Interaction to Next Paint (INP) metric, serves as one of the maintainers of the Core Web Vitals implementation, and contributes to the implementation of Web Performance APIs in Chromium. His current efforts include work on implementing Soft Navigation measurement. Outside of his professional role, he is a father to three boys and enjoys spending his time hiking, sailing, and woodworking.

React Rendering Techniques: Comparing Initial Load Performance

In the React community, we keep hearing that React Server Components (RSC) are the future. That they're supposed to be The Best for performance. And just the best in general. But is it true? What are those Server Components anyway? There is also Server-Side Rendering (SSR), is it the same? What about Client-Side Rendering (CSR), is it not cool anymore?

So many questions! To answer them, I went slightly crazy and implemented one app in three different ways: using CSR, SSR, and RSC. Then, measured the difference. And now, ready to show it to you.

In this talk, we'll take a look at the different rendering techniques in React, explore how they work, how they influence initial load numbers, look at what React Server Components bring to the table performance-wise, and dig into the cost of it.

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Nadia Makarevich

Nadia Makarevich is a seasoned developer, speaker, and writer. She has almost two decades of experience writing code, working in all types of companies, from small startups to five years at Atlassian.

She’s written extensively about React and web performance in her blog Developer Way, spoken at conferences worldwide, and authored two books: Advanced React and Web Performance Fundamentals.

Speculations about webperf

The Speculations Rules API brings a declarative way of "speculating" future navigations right into the browser with a simple JSON-based structure. In this talk you'll learn about all the features added to the API over the last year, learn how to safely deploy it on your site, and also get some hints about what to expect in the near future!

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Barry Pollard

Google

Barry Pollard works in the Chrome Developer Relations team specialising in web performance. He spends his days working on Core Web Vitals and tooling such as Chrome DevTools, PageSpeed Insights, the Chrome User Experience Report (CrUX), and maintaining the web-vitals JavaScript library. He's also a member of the W3C Web Performance Working Group. He is one of the maintainers of the HTTP Archive and its annual Web Almanac publication. He's the author of HTTP/2 in Action from Manning Publications. He frequently finds people who are wrong on the internet and this keeps him up at night. He also can't handle unread notifications on his phone so don't message him or he will answer you...

Teaching Agents about Performance insights

Everyone is shipping AI features or Agents, but few of those systems can reason with the complex reality of performance data. This session is a deep dive story into the journey of building a Performance AI assistant and agentic workflows on top of a fork of Chrome DevTools.

We'll explore practical lessons from DevTools internals on how to communicate performance data to Agents: teaching LLMs how to interpret performance data; which signals matter most; and how to transform telemetry into generated actionable insights from an LLM.

Building automated attribution on top of known performance metrics and data, and exploring how to leverage specialized agents with a few experiments using a custom MCP server so coding agents and perf data can collaborate for a better generative workflow.

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Vinicius Dallacqua

Lead developer, obsessed with browser internals, user experience and performance. I love working with performance and as of late AI workflows to empower applications to a new level. As a side project I am building a devtool called PerfLab and a performance expert agent called PerfAgent to express my vision of a modern tool focused on performance for developers of all expertise levels, leveraging AI and Web APIs to bring actionable insights to developers.

Fine-grained everything

Modern front-end frameworks like Svelte are astonishingly fast at rendering, thanks to techniques such as signal-based fine-grained reactivity. But there's more to performance than updating the screen at 60 frames per second. In this talk, we'll learn about new approaches that help you build fast, reliable, data-efficient apps.

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Rich Harris

Vercel

Rich Harris is the creator of several widely-used open source web development tools including Rollup, the JavaScript module bundler, and Svelte, a UI framework that obsesses over performance and accessibility.

Before joining Vercel, where he works full-time on Svelte, Rich was an award-winning visual journalist at the Guardian and the New York Times.