You probably checked your phone within ten minutes of waking up today. Don't feel bad. It’s not just "lack of willpower." It is by design. If you've ever wondered why some apps feel like a digital itch you have to scratch while others gather dust on page three of your home screen, you’re looking for the logic inside Hooked: How to Build Habit-Forming Products.
Nir Eyal wrote the book back in 2014, and honestly, it changed everything about how Silicon Valley thinks. But here is the thing: most people read the summary, try to "gamify" their app with some cheap points system, and then wonder why their retention rates are still garbage. Habits aren't about points. They are about emotions. Specifically, they are about alleviating pain.
The Hook Model isn't a checklist
It’s a loop. If you miss one part of the loop, the whole thing breaks.
Eyal breaks it down into four phases: Trigger, Action, Variable Reward, and Investment. Simple, right? Except it’s not. Most founders obsess over the "Action" part. They want the UI to be slick. They want the "Buy Now" button to be the perfect shade of orange. But they ignore the Internal Trigger.
An internal trigger is a feeling. Usually, a negative one. Boredom. Loneliness. Fear of missing out. Uncertainty. When you're standing in a long line at the grocery store and you feel that twinge of boredom, what do you do? You open Instagram. Instagram didn't send you a notification (that’s an external trigger). Your own brain sent the signal. The product became the solution to your boredom.
That is the holy grail. When a product is so ingrained in a user's life that they don't need a nudge to use it, you've won.
Triggers are the "Why" behind the "What"
You’ve got two types. External triggers are the easy ones. Emails, push notifications, icons, ads. They’re the "call to action." But they’re expensive and annoying. If you overdo it, people delete your app.
The real magic happens when you transition the user to internal triggers.
Think about Slack. At first, you get an email: "Your team is on Slack!" That’s external. But after a week, the trigger becomes the stress of wondering if your boss messaged you. The stress is internal. You open the app to kill the stress. Hooked: How to Build Habit-Forming Products argues that the goal of any habit-forming product is to attach itself to an existing itch in the user's daily routine.
If your product doesn't solve a frequent, recurring pain point—even a tiny one—it will never be a habit. It’ll just be a tool. Tools are used when necessary. Habits are used because it feels weird not to use them.
Why "Simple" always beats "Better"
The second phase is Action. This is where Fogg's Behavior Model comes in. B = MAT. Behavior equals Motivation, Ability, and a Trigger.
If you want someone to do something, it has to be brain-dead easy. If I have to click three times to find the search bar, I’m gone. Pinterest nailed this. The "Action" is just scrolling. No thinking required. Just infinite, mindless scrolling.
I’ve seen so many brilliant technical products fail because the "Action" was too high-friction. They had more features than the competition, but those features were buried. People are lazy. We follow the path of least resistance. To build a habit, the action must be simpler than the problem it’s solving.
The Slot Machine in your pocket
This is the part of Hooked: How to Build Habit-Forming Products that gets the most heat: Variable Rewards.
If you press a button and the same thing happens every time, you eventually stop pressing it. It's predictable. It's boring. But if you press a button and sometimes something amazing happens, and sometimes nothing happens? You become obsessed. This is "variable ratio reinforcement," a concept popularized by B.F. Skinner and his pigeons.
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- Rewards of the Tribe: Social validation. Likes, comments, retweets. We are social animals, and we crave the "hit" of being noticed.
- Rewards of the Hunt: The search for information or resources. This is the endless scroll on Twitter or the "deal hunting" on eBay.
- Rewards of the Self: Personal gratification. Clearing your inbox (Inbox Zero), leveling up in a game, or completing a task list.
The key here is variability. If every YouTube video was a masterpiece, you’d actually spend less time on the site because the novelty would wear off. You need the "meh" videos to make the "whoa" videos feel like a win.
The missing piece: Investment
Most apps let you leave too easily. Habit-forming products don't. They make you "invest" in them.
Investment isn't about money. It’s about data, effort, social capital, or time. Every time you follow someone on Twitter, you are investing. You are making the product better for you the next time you use it.
Think about Spotify. I’ve used it for years. It knows my taste better than my best friend does. If I switched to Apple Music today, I’d have to start over. I’d have to rebuild my playlists. I’d have to teach the algorithm what I like. That "switching cost" is the result of my investment.
The more "work" a user puts into a product, the more they value it. It’s the IKEA effect. We love the dresser more because we built it ourselves and cursed at the Allen wrench for three hours. In the digital world, this means letting users customize their profiles, build their reputations, or store their personal content.
Is this even ethical?
Honestly, it’s a gray area. Nir Eyal actually addressed this in the book with something he calls the "Manipulation Matrix."
He asks two questions:
- Does the product significantly improve the user's life?
- Does the creator use the product themselves?
If the answer to both is yes, you're a "Facilitator." You’re building something meaningful. If you’re building something that you know is addictive but doesn't actually help people (and you’d never use it yourself), you’re a "Dealer."
The line is thin. We’ve seen the fallout of habit-forming tech on mental health, especially with younger users. But the same principles that make TikTok addictive can also make a language-learning app like Duolingo work. The "hook" isn't inherently evil; it’s a tool. How you use it determines the impact.
Why most startups fail to build a "Hook"
I talk to founders all the time who say they’ve read Eyal’s book. Then I look at their product, and it’s a ghost town. Why?
Usually, it’s because they don’t have a Frequency of Use.
Habits require repetition. If your product is something people only need once every six months—like a mortgage calculator or a luggage-buying site—you cannot build a habit. Period. You have to rely on SEO or ads. For a habit to form, the behavior usually needs to happen within a week, if not daily.
The second reason is that the "Reward" isn't actually rewarding. Many B2B SaaS companies think "getting a report" is a reward. It’s not. It’s work. A real reward creates a dopamine spike. It feels like progress or discovery. If your product feels like a chore, no amount of "variable rewards" will save it.
Practical Steps to Apply the Hook Model
If you’re sitting there with a product that isn't "sticking," don’t just add a progress bar and call it a day. Do this instead:
Audit your Triggers.
Ask your users what they were doing right before they opened your app. Not the "official" reason, but the real one. Were they bored? Stressed? On the toilet? Identify that "itch." If you can't name the internal trigger, you don't have a habit-forming product.
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Slash the friction.
Look at your onboarding flow. Then delete half of it. Every field a user has to fill out is a chance for them to leave. Can you get them to the "Variable Reward" in under 30 seconds? If not, you’re losing people.
Find the "Investment" moment.
What is the one thing a user can do that makes the app better for them tomorrow? Is it adding a friend? Uploading a file? Starring a favorite? Force that action early. Make them "own" a piece of the experience.
Test for variability.
If your user experience is the same every single time, find a way to inject some mystery. Maybe it’s a "discovery" feed. Maybe it’s a surprise notification. Give them a reason to check "just in case" something new is there.
Building a habit-forming product isn't about tricking people. It’s about understanding human psychology well enough to give people what they actually want, before they even realize they want it. It's a high-stakes game. But if you get the loop right, you don't just have customers—you have fans.
Actionable Roadmap for Product Teams
- Identify the "Pain Point": Map your product features to specific negative emotions (e.g., "I feel disorganized, so I open Trello").
- Simplify the "Core Action": Use the Fogg Behavior Model to identify where Ability is lacking. Use heatmaps like Hotjar to see where users get stuck.
- Audit Variable Rewards: Ensure your rewards aren't just "transactional." They should feel like a discovery or a social win.
- Focus on Store Value: Ensure that as the user interacts, the product becomes a "repository" of their effort. This creates the "loss aversion" that keeps them from leaving.
- Ethical Check: Run the Manipulation Matrix. If you wouldn't want your kids using the product for hours a day, rethink the mechanics.