Hooked: the four phases of a habit-forming product

Who should use it, and when not to

Use it when people sign up and try a product, then don't come back, or before adding notifications, streaks or rewards. It fits products whose value depends on frequent use: daily or weekly.

It fits poorly for products used once a year, such as tax filing; better onboarding and reminders matter more there. And if you don't yet know whether the product solves a real need, start with The Lean Product Playbook.

The core ideas

Triggers. External triggers tell the user what to do next: a button, an email, a message from a colleague. Internal triggers are emotions or situations, such as not knowing today's prices or feeling behind on work. Eyal argues the products that form habits are those that attach themselves to an internal trigger.

Action. The easier the action, the more likely it happens. Cut steps between the trigger and the reward.

Variable reward. A reward that is always the same loses its pull. Eyal describes three kinds: rewards of the tribe (social), the hunt (resources or information) and the self (mastery or completion).

Investment. Users put in data, content, followers, settings or skill. Stored value makes the product better with use and harder to leave, and an investment can load the next trigger, such as a reply that will arrive later.

Ethics. Eyal frames habit design as a responsibility and offers a check on whether the product improves the user's life. His later book, Indistractable (2019), is about resisting unwanted habits.

A worked mini example

This is an illustration. An app lets restaurant managers in Bogotá order produce from local suppliers. 61% of new managers place a first order; only 18% order in week four. Repeat managers almost all use "reorder last basket". The only trigger is a weekly promo email. Managers say they open the app to check whether tomato prices fell.

How to review your product's loop

1. Set the habit target: who does what, how often.
2. Name the internal trigger, in users' words.
3. Review external triggers: when each fires, and whether it leads to one action.
4. Count the steps to the reward, and find where people stop.
5. Check the reward varies in a way users care about.
6. List what users invest and whether it improves the next visit.
7. Fix the weakest phase first, then run the ethics check.

The habit loop review skill runs these steps with your usage data and drops ideas that rely on compulsion.

Common mistakes

• More notifications instead of a real internal trigger. Users learn to ignore them.
• Rewards that never change. They stop pulling people back.
• No investment. Each visit starts from zero.
• A habit users wouldn't choose. It may raise usage for a while, and trust falls.

Where it comes from

Nir Eyal developed the Hooked Model on his blog, Nir and Far, and published Hooked: How to Build Habit-Forming Products in 2014, written with Ryan Hoover. It became a Wall Street Journal best-seller. Critics have argued that habit design contributes to compulsive technology use; Eyal's 2019 book Indistractable addresses how users can control their attention.

This page is an independent summary in our own words. It is not affiliated with or endorsed by Nir Eyal or his publishers. The book's title is used only to name it. More explainers are in the business books index.

Questions

What is the Hooked Model?

Nir Eyal's four-phase loop for products people use out of habit: a trigger prompts use, the user takes a simple action, gets a variable reward, and invests something that makes the product better next time and sets up the next trigger.

What is the difference between external and internal triggers?

External triggers are cues in the world, such as a notification or an email. Internal triggers are feelings or routines, such as boredom or uncertainty, that bring the user back without a prompt. A habit forms when internal triggers take over.

Is designing for habits ethical?

It can be either. A habit that helps users do what they already want is useful. One that exploits compulsion is not. Eyal suggests asking whether the product improves users' lives and whether you would use it yourself.