Hooked: How to Build Habit-Forming Products
By Nir Eyal
What social media platforms or applications are you hooked on?
The power of AI algorithms has exponentially expanded the ways we can become attached to information technology products and services, for better or for worse.
As someone who gambled compulsively for much of my twenties and came through the other side of addiction, and as someone who has spent the last 2 decades helping businesses increase customer reliance, this book was an important read for me, both personally and professionally.
What causes us to develop habits, regardless of whether we perceive them as healthy or unhealthy?
This book is written by someone who clearly understands the commercial “Hooked Formula” used by some of the largest and most powerful businesses in the world.
Nir Eyal shares a simple yet powerful framework. He comes from the right place in encouraging ethical application, and he does acknowledge that being “hooked” on a product or service can be destructive. However, he largely avoids the negative connotations of addiction and instead emphasises positive use cases.
Eyal cites two successful applications that applied this approach effectively: a Bible reading app (Bible.com), and a fitness app called Fitbod. In both cases, the products helped people do more of what they already wanted to do read the Bible more consistently or exercise regularly. Excessive bible reading or excessive exercise rarely create personal crises or societal problems. Eyal also shares his own long personal struggle with maintaining a consistent exercise habit and how Fitbod, built around the Hooked Formula, helped him overcome it.
Regardless of whether being “hooked” on a product or service is empowering or disempowering, I believe that simply understanding what hooks us is, in itself, deeply empowering.
Beyond personal awareness, the commercial and business implications of understanding the Hooked Formula are significant.
Never before in human history has addictive behaviour been so openly prevalent. The next time you are out in public, observe how many people have their attention fixed on a mobile phone or device, standing in queues, sitting on buses or trains, or in cafés. Many are actively engaged in what is now known as doom-scrolling, or seeking some form of digital escapism through entertainment or gaming.
“Doom-scrolling” refers to consuming an endless stream of negative news about how broken the world is. The flip side is using the internet to escape from that same reality.
So, let’s dive into the book.
Introduction – Why Habits Matter in Products & Services
In a world saturated with apps, services, and products, the most successful ones don’t just attract users temporarily, they become part of daily life. Think of the apps you instinctively open each day without conscious thought: social platforms, messaging services, news feeds. What makes these products so sticky?
Nir Eyal explores the psychology and design strategies behind habit-forming products. This is not just theory; it is a practical guide for founders, designers, builders, and product teams who want their creations to become indispensable. At its core, the book examines how products influence behaviour over time, not primarily through advertising, but by embedding themselves into users’ routines.
“Habits are behaviours performed with little or no conscious thought.”
When product use becomes habitual, users return frequently, increasing engagement, loyalty, and long-term value. Habit formation can be the difference between a product people briefly try and one they rely on daily.
The Habit Zone
Eyal introduces the concept of the Habit Zone, the intersection where frequency of use and perceived utility meet. When a product is used often enough and provides sufficient value, habits are far more likely to form.
Frequency alone is not enough. A product used infrequently but with high utility (such as a travel booking site) can still be habit-forming. Conversely, a frequently used product with little perceived value will not stick. The key lies in repeatedly solving real user problems or meeting deep motivations.
Habit-forming products deliver predictable value at moments of need. Over time, this repeated interaction becomes automatic and something users do without conscious deliberation.
The Hook Model: A Four-Step Framework
At the heart of the book is the Hook Model, a cyclical framework that explains how habits are formed. It consists of four stages:
- Triggers
- Actions
- Variable Rewards
- Investment
Repeatedly cycling users through these stages strengthens the habit loop, gradually shifting reliance from external prompts to the internal triggers of emotions, thoughts, or urges that drive behaviour without conscious awareness.
Let’s examine each step.
- Triggers – The Spark of Behaviour
Triggers prompt users to act. They come in two forms.
External Triggers
These are cues in the user’s environment, such as:
- Notifications
- Emails
- Ads
- App icons
- Social media links
External triggers are essential for early engagement but are costly and ineffective over time if relied upon exclusively.
Internal Triggers
Internal triggers are emotional associations stored in the user’s mind. Over time, products become linked to feelings such as boredom, loneliness, stress, or uncertainty.
- Boredom may prompt opening a social feed
- Anxiety may drive email checking
- Fear of missing out may trigger messaging apps
Internal triggers are far more powerful because they originate within the user. The ultimate aim of habit design is to shift reliance from external cues to internal emotional states.
Eyal stresses the importance of identifying users’ internal pains, emotions, and unmet needs. The most effective products become so tightly linked to these states that the product is the automatic response.
- Actions – The Simplest Behaviour
After a trigger, the user must take the action and behaviour the product is designed to encourage.
Eyal draws on B.J. Fogg’s Behaviour Model:
“Behaviour occurs when Motivation, Ability, and a Trigger converge.”
- Motivation: Does the user want to act?
- Ability: Is it easy to act?
- Trigger: Is there a prompt?
The simpler the action and the stronger its alignment with user motivation, the more likely it is to occur. Reducing friction, fewer steps, intuitive design, and simple onboarding, dramatically increases engagement.
Quick taps, swipes, or scrolls outperform complex processes because they lower the effort required to act.
- Variable Rewards – The Craving Generator
After action comes reward, but not a fixed reward! Variable rewards are unpredictable, and that uncertainty fuels craving by activating dopamine pathways.
Examples include:
- Gambling machines
- Social media likes
- Infinite scroll feeds
- Surprise content or offers
Eyal identifies three types of variable rewards.
- a) Rewards of the Tribe
Social validation such as likes, comments, shares, recognition, community. - b) Rewards of the Hunt
The search for information, content, or value. Endless scrolling in search of something interesting is a classic example. - c) Rewards of the Self
Intrinsic rewards such as mastery, progress, and achievement like clearing an inbox, levelling up, or completing a challenge.
Crucially, rewards must align with user motivations. Gamification alone fails if it does not connect to something users genuinely care about.
- Investment – Loading the Next Hook
Investment occurs when users put something of value into the product including their time, effort, data, preferences, connections, or content.
Investment serves two purposes:
- It increases personal commitment
- It loads the next trigger
Examples include:
- Uploading photos
- Setting preferences
- Adding contacts
This is linked to the IKEA effect: we value things more when we help build them. Each investment strengthens the habit loop and raises the cost of switching away.
Habit Testing & Application
Eyal complements theory with practical guidance on testing and refining habit-forming products. He emphasises that not all products should form habits. Durable goods, such as insurance or furniture, do not require daily engagement. Digital platforms and apps benefit most.
Designers are encouraged to understand why users want the product, what internal trigger it addresses, and where frequency can naturally emerge.
Ethical Considerations
A knife can prepare a healthy meal or cause harm. The tool is neutral, it is the intent of the individual using the knife that matters. The same applies to the Hooked Formula.
Eyal urges creators to ask:
- “Would I use this product myself?”
- “Does this product materially improve users’ lives?”
If not, the design risks exploitation rather than service. Ethical habit formation is about enabling positive behaviours, not addiction.
Real-World Examples
Eyal references familiar applications:
- Social media: triggers, scrolling rewards, social validation, profile investment
- Messaging apps: emotional triggers, unpredictable conversations, social investment
- Games: progress, achievements, and customisation
These examples demonstrate how habit loops operate across industries.
Conclusion
Hooked provides a clear, practical framework for understanding and designing habit-forming products, blending behavioural psychology with real-world application.
At its core:
- Triggers initiate behaviour
- Actions simplify engagement
- Variable rewards sustain interest
- Investment builds commitment
Repeated cycles turn casual users into habitual ones, while reminding creators of the responsibility that comes with influence.
My Recommendation
I recommend Hooked to anyone seeking to understand their own habits around products and services. I would equally recommend it to leaders working in the business of product & service design, service delivery, marketing and human behaviour.