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Website Performance Optimization

Free Course

The Critical Rendering Path

Related Nanodegree Program

Introduction to Programming

In collaboration with
  • Google

About this course

You will learn how to optimize any website for speed by diving into the details of how mobile and desktop browsers render pages.

In this short course, you’ll learn about the Critical Rendering Path, or the set of steps browsers must take to convert HTML, CSS and JavaScript into living, breathing websites. From there, you’ll start exploring and experimenting with tools to measure performance and simple strategies to deliver the first pixels to the screen as early as possible. You’ll learn how to dive into recommendations from PageSpeed Insights and the Timeline view of Google Chrome’s Developer Tools to find the data you need to achieve immediate performance boosts!

This course is also a part of our Front-End Web Developer Nanodegree.

What you will learn

  1. Introduction
    • Intro to Chrome Developer Tools.
    • How to measure the performance of mobile and desktop websites.
  2. Critical Rendering Path
    • How are browsers and websites built.
    • HTML, CSS and JavaScript and the conversions to DOM and CSSOM.
    • Measuring performance via the Timeline view in Chrome Developer Tools.
  3. Easy HTML, CSS and JavaScript optimizations.
    • Adding powerful attributes to HTML tags.
    • Diagnose opportunities for optimization.
    • Key metrics to triangulate potential performance bottlenecks.

Prerequisites and requirements

This course is for any and all web developers, whether you started learning about HTML, CSS and JavaScript recently or have been building websites since the nineties!

Most importantly, you should be able to explain the overall purpose of HTML, CSS and JavaScript with respect to website structure. In addition, you should be comfortable reading and writing HTML documents and modifying JavaScript files.

This course is taught with Google Chrome and Google Chrome Canary.

See the Technology Requirements for using Udacity.

Why take this course?

From Ilya Grigorik's High Performance Browser Networking:

"The emergence and the fast growth of the web performance optimization (WPO) industry within the past few years is a telltale sign of the growing importance and demand for speed and faster user experiences by the users. And this is not simply a psychological need for speed in our ever accelerating and connected world, but a requirement driven by empirical results, as measured with respect to the bottom-line performance of the many online businesses:

  • Faster sites lead to better user engagement.
  • Faster sites lead to better user retention.
  • Faster sites lead to higher conversions.

Simply put, speed is a feature."


You will optimize an online portfolio for speed, which you can share with the world to showcase your skills!

Making a great first impression is absolutely key and an online portfolio can help you stand apart from the crowd. We’ll give you a template for a modern, mobile-friendly portfolio which you’ll be able to completely customize so that it shows off your work and your skills the way you want. But before you show it off to the world, you’ll practice your web performance skills by optimizing the portfolio to render as fast as possible.

Learn with the best.

  • Cameron Pittman
    Cameron Pittman


  • Ilya Grigorik
    Ilya Grigorik