Professor Sloth

Security Update

In the wake of AI-fueld security incidents, we're auditing all our systems and practices. Here's how we protect the Request Metrics agent from attack, and how to host it yourself.

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Web Performance Blog

The latest tips, tricks, and research to make your website fast.

  • How We Protect Our JavaScript Agent, and How to Host It Yourself

    How We Protect Our JavaScript Agent, and How to Host It Yourself

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  • Understanding Lighthouse: Speed Index

    Understanding Lighthouse: Speed Index

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  • Understanding Lighthouse: First Meaningful Paint

    Understanding Lighthouse: First Meaningful Paint

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  • Understanding Lighthouse: Largest Contentful Paint

    Understanding Lighthouse: Largest Contentful Paint

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  • Understanding Lighthouse: First Contentful Paint

    Understanding Lighthouse: First Contentful Paint

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  • Understanding Lighthouse: Has a Viewport Meta Tag

    Understanding Lighthouse: Has a Viewport Meta Tag

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  • New Option: Preserve URL Casing

    New Option: Preserve URL Casing

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  • The Limitations of Lighthouse

    The Limitations of Lighthouse

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  • Why You Need Real User Monitoring to Really Understand Your Web Performance

    Why You Need Real User Monitoring to Really Understand Your Web Performance

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  • Synthetic Testing and Real User Monitoring

    Synthetic Testing and Real User Monitoring

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  • HTTP Caching Headers: The Complete Guide to Faster Websites

    HTTP Caching Headers: The Complete Guide to Faster Websites

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  • GTMetrix Alternatives: The Best Tools for Website Performance Testing

    GTMetrix Alternatives: The Best Tools for Website Performance Testing

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  • HTTP/3 is Fast!

    HTTP/3 is Fast!

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  • 5 Tips To Make Google Fonts Faster

    5 Tips To Make Google Fonts Faster

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  • How to Optimize Website Images: The Complete 2026 Guide

    How to Optimize Website Images: The Complete 2026 Guide

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  • How to Use wp_redirect in WordPress

    How to Use wp_redirect in WordPress

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  • Unified Web Performance: Real User Monitoring and Automatic Lighthouse Testing

    Unified Web Performance: Real User Monitoring and Automatic Lighthouse Testing

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  • Fixing Long Animation Frames (LoAF)

    Fixing Long Animation Frames (LoAF)

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  • Request Metrics and Perforator - Combining RUM and Load Testing

    Request Metrics and Perforator - Combining RUM and Load Testing

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  • What are Long Animation Frames (LoAF)?

    What are Long Animation Frames (LoAF)?

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  • The Chrome UX Report: Why Real Data Matters

    The Chrome UX Report: Why Real Data Matters

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  • Launching Resource Performance Monitoring

    Launching Resource Performance Monitoring

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  • How to Monitor Cross-Origin Resource Performance

    How to Monitor Cross-Origin Resource Performance

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  • Improving Your Interaction to Next Paint (INP)

    Improving Your Interaction to Next Paint (INP)

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  • Trying and failing and trying again

    Trying and failing and trying again

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  • Frontend vs Backend Performance: Which is Slower?

    Frontend vs Backend Performance: Which is Slower?

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  • What is a 'Rage Click'?

    What is a 'Rage Click'?

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  • What Is Time to Interactive? A Comprehensive Guide

    What Is Time to Interactive? A Comprehensive Guide

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  • Announcing Custom Metadata Reports & Filters

    Announcing Custom Metadata Reports & Filters

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  • Debugging a Slow Core Web Vital Score

    Debugging a Slow Core Web Vital Score

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  • Google Analytics 4 Has Me So Frustrated, We Built Our Own Analytics Service

    Google Analytics 4 Has Me So Frustrated, We Built Our Own Analytics Service

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  • Our Super Friendly AI Sloth that Analyzes Your Performance Data

    Our Super Friendly AI Sloth that Analyzes Your Performance Data

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  • Svelte vs. React: Which is Better for Performance?

    Svelte vs. React: Which is Better for Performance?

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  • Measuring Web Performance in 2024: The Definitive Guide

    Measuring Web Performance in 2024: The Definitive Guide

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  • CSS Image Effects: A Detailed Guide

    CSS Image Effects: A Detailed Guide

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  • Explaining Performance to Non-Technical Stakeholders

    Explaining Performance to Non-Technical Stakeholders

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  • Audit Google Ad Performance With Lighthouse

    Audit Google Ad Performance With Lighthouse

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  • How To Read Flame Charts and Percentiles

    How To Read Flame Charts and Percentiles

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  • Google Ads Are Slowing You Down

    Google Ads Are Slowing You Down

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  • See Current Core Web Vitals with Chrome

    See Current Core Web Vitals with Chrome

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  • Optimizing Static HTML And Images With Webpack

    Optimizing Static HTML And Images With Webpack

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  • Optimizing Images for Web Performance with NGINX

    Optimizing Images for Web Performance with NGINX

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  • Fast Inline Images With React and Webpack

    Fast Inline Images With React and Webpack

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  • Using Brotli Compression in NGINX

    Using Brotli Compression in NGINX

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  • Advertising's Performance Tradeoffs

    Advertising's Performance Tradeoffs

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  • Fix Your First Contentful Paint (FCP): Cheat Sheet

    Fix Your First Contentful Paint (FCP): Cheat Sheet

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  • Using First Contentful Paint (FCP)

    Using First Contentful Paint (FCP)

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  • Tutorial: Monitoring Your Core Web Vitals

    Tutorial: Monitoring Your Core Web Vitals

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  • How Hacker News Crushed DavidWalshBlog

    How Hacker News Crushed DavidWalshBlog

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  • Web Performance Profiling: Instacart.com

    Web Performance Profiling: Instacart.com

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  • Vital Web Performance

    Vital Web Performance

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  • Web Performance Profiling: Google.com

    Web Performance Profiling: Google.com

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  • Measuring First Input Delay (FID)

    Measuring First Input Delay (FID)

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  • Web Performance Profiling: Nike.com

    Web Performance Profiling: Nike.com

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  • Privacy and Ethical Web Analytics

    Privacy and Ethical Web Analytics

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  • Measuring Largest Contentful Paint (LCP)

    Measuring Largest Contentful Paint (LCP)

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  • Fastest News: Best Performing News Website

    Fastest News: Best Performing News Website

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  • Measuring Cumulative Layout Shift (CLS)

    Measuring Cumulative Layout Shift (CLS)

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  • Breaking Out of Webpack Based Build Chains

    Breaking Out of Webpack Based Build Chains

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  • Using the Beacon API

    Using the Beacon API

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  • Using NGINX as a Queue for JSON Data

    Using NGINX as a Queue for JSON Data

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  • Episode 17: User Sign Up and Simple Access Control

    Episode 17: User Sign Up and Simple Access Control

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  • Episode 16: Using Redis for Distributed User Sessions in ASP.NET Core

    Episode 16: Using Redis for Distributed User Sessions in ASP.NET Core

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  • Episode 15: Simple Cookie Based Authentication in ASP.NET Core

    Episode 15: Simple Cookie Based Authentication in ASP.NET Core

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  • Episode 14: Storing User Data In Redis

    Episode 14: Storing User Data In Redis

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  • Episode 13: Testing In .NET Core Using NUnit

    Episode 13: Testing In .NET Core Using NUnit

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  • Episode 12: Tweaking Systemd Services With Ansible

    Episode 12: Tweaking Systemd Services With Ansible

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  • Episode 11: Connecting to Redis in .NET Core 3.1

    Episode 11: Connecting to Redis in .NET Core 3.1

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  • Episode 10: Installing Redis Using An Ansible Galaxy Role

    Episode 10: Installing Redis Using An Ansible Galaxy Role

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  • Episode 9: Running ASP.NET Core Applications Using Systemd and Ansible

    Episode 9: Running ASP.NET Core Applications Using Systemd and Ansible

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  • Episode 8: Using Ansible to Configure NGINX for ASP.NET Core

    Episode 8: Using Ansible to Configure NGINX for ASP.NET Core

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  • Episode 7: Using Ansible Roles for Common Linux Settings

    Episode 7: Using Ansible Roles for Common Linux Settings

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  • Episode 6: Buying an SSL Certificate

    Episode 6: Buying an SSL Certificate

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  • Episode 5: Let's Encrypt? Let's Not.

    Episode 5: Let's Encrypt? Let's Not.

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  • Episode 4: Deploying Code to Linux From TeamCity

    Episode 4: Deploying Code to Linux From TeamCity

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  • Episode 3.5: Basic Ansible With SSH Keys

    Episode 3.5: Basic Ansible With SSH Keys

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  • Episode 3: SSH Keys For Server Authentication

    Episode 3: SSH Keys For Server Authentication

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  • Episode 2: Building the Code

    Episode 2: Building the Code

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  • Episode 1: File->New Project

    Episode 1: File->New Project

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  • Episode 0: Introducing Request Metrics!

    Episode 0: Introducing Request Metrics!

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