From beginners to experts, everyone has gaps. This is the only course that teaches React from its actual source code. Master Fiber internals, reconciliation, and build the deep mental models that empower you to solve every React challenge.
by Tony Alicea
📣 Updated for React 19!
📣 Bundle With Upcoming State Management Add-On! Dive deeper into React State Management with Jotai, Zustand, XState, and TanStack Query!
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You're about to master React in a way that few others do. By truly understanding it, under-the-hood. From JSX transpilation to React Fiber and more.
31 modules
164 lessons
17 hours of video
React is a required skill in the modern web development job market. But even devs experienced in React struggle with understanding it fully, and thus struggle with writing efficient code and debugging it quickly.
Maybe you've spent lots of time mimicing instructors, typing what they type like following a GPS. The problem is that doesn't lead to true understanding. If you don't understand the roads, you can't find your way when you face a roadblock.
In this course, you'll gain the most powerful tool a developer can have: an accurate mental model - which leads to unparalleled confidence and calm while coding.
I've read all of React's source code for you, and you're about to dive into it with me. Whether new or experienced, you're about to understand React.
★★★★★
"This should be a must-take course for any React developer (even more so for people like me, with 4 years of experience, and I learned A LOT here). Every section is carefully constructed to build on the previous one and build a greater knowledge of React. You cannot say you understand React until you have studied with Tony Alicea."
Hi, I'm Tony Alicea. I've been an application developer, database architect, UX designer, and tech educator for over 25 years.
Over 360,000 students have enrolled in my courses on Udemy, Pluralsight, and Teachable. I've been a speaker at conferences like React Summit, the biggest React conference in the world. You can read more about me and my courses on my site.
But I Already Know React!
A lot of developers have experience using React, and have built things with it! But that's not the same thing as the cool confidence that comes from understanding how React works.
I've given talks on React and watched as a room full of devs currently using React drop their heads and start frantically writing notes as they see how React internals work. Why? Because there is great value in deeply understanding.
Understanding yields better coding choices and most strikingly faster, easier debugging. When you know how something works it's far easier to fix things when something goes wrong.
That's what you'll get in this course. I'm proud to say experienced React devs, after taking this course, have said that an accurate mental model has changed their dev life.
But I Don't Know React!
That's great! Then you don't have any incorrect mental models to undo.
This course will take you up from the very beginnings of the problems React was designed to solve, through JSX, how React works under-the-hood, and more.
It's also perfect for people who've never used React at all.
Don't Imitate, Understand
A lot of courses will use terms like "deep dive" and "under-the-hood", but not actually provide deep understanding.
I call the technique I use "don't imitate, understand". If you just parrot what the instructor is typing on the screen you might end up with a finished product. But as soon as you're dealing with challenges and problems in a real-world job, you'll realize the parroting didn't teach you all that much.
Instead of spending hours imitating me typing, we're going to dive deep together into React's source code to truly, deeply understand it.
We'll write plenty of code along the way, including project work. But we won't write a line of code we don't fully break down and understand.
JavaScript, Browsers, and Computer Science
As we dig into React's internals, we'll discuss the underlying algorithms and data structures you need to know to understand React.
We'll stop and spend time analyzing the vocabulary of React, making sure we don't use any terms that aren't clearly explained.
We'll approach React like a computer scientist. React is just other people's JavaScript code. So why did they write the code they wrote? Why does React work the way it does? What are the benefits? What are the pitfalls?
We'll also look at JavaScript and browser concepts that underpin React's choices and best practices. Things like immutability, object references, and the browser rendering engine. All of this to service using and debugging React well.
These topics will take rules that normally would be memorized (like the rules of Hooks, "pure" component functions, and things you can't do in JSX) and instead be able to derive those rules ourselves naturally by understanding how components and Hooks are structured and work inside React.
We'll write plenty of code along the way, including project work. But we won't write a line of code that we don't already fully understand.
The Fiber Tree: Deep React Internals
A foundation of our understanding of React will be the tree data structure.
Understanding React actually means understanding three trees. The DOM, the React Element Tree, and vitally, the Fiber Tree.
Understanding core React concepts like JSX, Hooks, reconciliation, and events properly all rely on understanding the Fiber Tree, as well as core data structures like Linked Lists and Queues. In this course we cover them all together.
100s of Animations
We won't just look at code. I've put together hundreds of animations so that you can visualize what the React is doing internally and fully understand it.
Then, we put that newfound mental model to use as we build your React knowledge piece-by-piece, and work through code examples together.
The Curriculum
The course contains 17 hours of video and is split into 31 modules. I've designed the course to be useful and accessible to developers new to React and will provide a deeper mental model and understanding to devs experienced in React.
You'll also get access to 80 zip files containing the code in the lectures so you can compare with your own.
And you can always ask questions in the lecture forums, where I answer personally.
The course covers a wide range of topics in a logical, progressive order. From JSX to Hooks to State and Context to React Server Components and so much more.
There's another thing I show you here that other courses don't. Rather than adding <div> elements everywhere, I show you how to think through marking up your React components with semantic, accessible HTML that improves your code's readability, maintainability, and SEO.
What Others Are Saying
★★★★★
I highly recommend this course! Even for devs who have worked in React for years. Tony's way of digging through the source code under the hood has completely changed my mental model. Incredibly valuable.
Heather M.
This is the best React course I have taken and I have taken a few to be honest. You have overdelivered on this Tony.
Eyitayo O.
A masterpiece of React course. Deep dive and truly understanding how things work is undoubtedly the mindset all developers must have. And Tony once again nailed it with this course.
Sy P.
Thank you Tony, for spending the time to approach React from a deeper perspective.
Nicolas G.
I have clear picture now how React is working under the hood. And also the last project was fun.
Matija R.
Remarkable course.
Nilkamal S.
Magnificent!
Miroslav M.
As a self-taught developer who transitioned from education to tech, his teaching style resonates with my teacher training – exploring the "why" instead of just the "how", gradual build up of concepts, simple explanation of technical jargons, etc. The feeling of true understanding is a deep satisfaction that hacky tricks will not achieve.
Shelly C.
Watch The First 6 Hours For Free
I'm confident you will find this technique to be game-changing. I've seen it happen for students for a decade. It's how I've learned things during my 25 years of web dev.
I'm so confident it will help you, that I put the first 6 hours of the course for free on my YouTube channel. Feel free to watch here.
There's enough free training here, that even if you don't enroll in the full course you'll learn something about React that you didn't know before.
Join 1,426 Students and Gain Deep Understanding
An accurate mental model will forever benefit your dev career.
Understanding React Core
The 17-hour Core Course
$179
Lifetime Access
Tax/VAT Included
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INCLUDES
✓ 17 hours of deep dive video
✓ 31 modules (164 lessons)
✓ All source code
✓ Certificate of completion
✓ Questions answered by me personally
✓ Free future updates
✓ 30-day money back guarantee
Understanding React Complete
The 17-hour Core plus The Upcoming State-Management Add-On
$279
The 17-Hour Core Course
Pre-Sale Price for Upcoming Add-On!
Jotai, Zustand, XState, TanStack Query
Lifetime Access
Tax/VAT Included
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INCLUDES
✓ Everything in Understanding React
✓ Pre-Sale for State Management in React (Jotai, Zustand, XState, TanStack Query)
Team Discounts (Understanding React Complete)
Get Multiple Licenses for The 17-hour Core plus The Upcoming Add-On
$916
Lifetime Access
Tax/VAT Included
💡 You'll receive special team links to enroll within 24 hours.
📧 Send a note to support@tonyalicea.dev to request an invoice or for purchases for more than 10 seats.
Group & Community Rates
I offer significant discounts for student cohorts, bootcamps, learning groups, and community organizations.
Whether you're organizing a study group, running an educational program, or looking to bring React training to your community, I'm happy to work with you on pricing that makes sense for your situation. Reach out to hey@tonyalicea.dev with details about your group.
FAQs
How do team licenses work?
Within 24 hours of purchase you'll receive a list of links, one for each license. Each team member may then use their own link to enroll for free with their own login.
Do you offer Purchasing Power Parity (PPP) or student discounts?
Yes, I believe in PPP and student discounts. You can fill out a request form here. PPP coupons are sent out every couple of weeks.
Is this a subscription?
No. This is a one time purchase for lifetime access to the course and all future updates.