The principles behind the notes
Every note in the teardowns names a principle. Here's what each one means, the research behind it, and every screen where it shows up.
Behavioral effects 18
Default effect
People tend to stick with whatever option is preselected, so the default often decides the outcome for most users.
Anchoring
The first number or option people see becomes a reference point that pulls later judgments of price and value toward it.
Social proof
People look to what others like them do or choose when deciding what to do themselves, especially when unsure.
Goal-gradient effect
People put in more effort the closer they feel to finishing, so visible progress toward a near goal speeds them up.
Aesthetic-usability effect
People judge attractive, polished interfaces as easier to use and more credible, and forgive them small problems.
Framing
The same facts lead to different choices depending on how they are described, for example as gains or losses.
Loss aversion
A loss tends to feel bigger than a gain of the same size, so framing what users stand to lose can motivate action.
Reason-giving
People are more willing to agree to a request when it comes with a short reason that says why it is asked.
Reciprocity
When someone gives us something first, we feel inclined to give something back.
Urgency
A real deadline gives people a reason to act now instead of putting off a decision they already intend to make.
Endowed progress effect
People work harder to finish a goal when they are given a head start, even if the head start is artificial.
Habit formation
Repeating an action in the same context, with a cue and a reward, gradually makes it automatic so people return without deciding to.
Scarcity
Things seem more valuable when they are limited or running out, which makes real limits and quotas strong prompts to act.
Choice overload
Too many options, or options that look alike, can make people delay, choose badly or not choose at all.
Decoy effect
Adding an option that is clearly worse than one of the others makes that other option look better and more likely to be chosen.
Endowment effect
People value something more once they own it or have put work into it, so giving it up feels costly.
Labor illusion
People value a result more when they can see the work that went into producing it, even if it takes longer.
Zeigarnik effect
Unfinished tasks tend to stay on people's minds and pull them back, so a visible "you started this" prompt can bring users back.
Usability heuristics 20
Clarity
Every word, label and visual on a screen should mean one thing and match what actually happens when the user acts.
Transparency
Show the full price, terms and data use up front, in plain words, so people know exactly what they are agreeing to.
Show, don't tell
Let people see or try the product's result, with examples, previews or demo data, instead of describing features in words.
User control and freedom
Give people a clear way to skip, go back, undo or leave, so no step traps them in a flow they did not choose.
Visibility of system status
Keep users informed about what the system is doing and what their actions caused, through timely, clear feedback.
Visual hierarchy
Use size, contrast, color and position so the most important element on a screen is the one people see and act on first.
Contextual help
Guidance that appears inside the real interface at the moment and place a user needs it, rather than up front.
Progressive disclosure
Show the few options most people need first, and move advanced or rarely used details to a second step.
Discoverability
Make features, options and content easy to come across, with clear cues that say what they are and why they are worth a click.
Signal vs noise
Every extra element, alert or interruption competes with what matters on the screen, so cut anything that doesn't help the current task.
Consistency and standards
Make the same thing look, read and behave the same way everywhere, and follow the conventions people already know from other products.
Recognition over recall
Show options, labels and previous inputs on screen so users can pick what they need instead of remembering it.
Clear call to action
Each screen has one obvious next step, and its button says exactly what will happen when you press it.
Flexibility and efficiency of use
Offer more than one way to get a task done, with shortcuts and fallbacks, so both new and experienced users can move at their pace.
Error prevention
Design screens so mistakes are hard to make: constrain input, check it as people type, and confirm only risky actions.
Cognitive load
Working memory is small, so every extra thing users must read, compare or remember leaves less for the actual decision.
Mental models
Users act on their own beliefs about how a product works; designs that match or clearly teach those beliefs are easier to use.
Expectation setting
Tell people before they start what a step will ask of them, how long it will take, and what will happen afterward.
Preserve context
Carry the user's choices, location and purpose through each step so they never have to re-enter, re-choose or reorient.
Affordance
An element's look should signal what you can do with it: buttons look pressable, carousels look swipeable, text looks like text.
Product patterns 16
Reduce friction
Remove the steps, typing, decisions and waits that stand between a user and the thing they came to do.
Trust signals
Cues that answer a user's unspoken worry (spam, surprise charges, security, accuracy) at the moment the worry arises.
Personalization
Adapting content, examples or offers to what you know about the user, so the product feels built for their situation.
Time to value
Shorten the time between signup and the first moment the product does something useful for this user.
Contextual timing
Show an offer, request or prompt when the user's current task makes it relevant, not on a fixed schedule.
Risk reversal
Lower the cost of saying yes by moving the risk off the user: free trials, no card required, refunds, easy cancellation.
Informed consent
Ask for data, permissions and marketing opt-ins in a way users understand, with a real choice and no preselected yes.
Network effects
A product becomes more valuable to each user as more people use it, so inviting, sharing and joining teammates drive both value and growth.
Specificity
Concrete numbers, names and examples persuade and inform better than vague claims like "improved" or "some".
Value metric pricing
Charging along the unit that grows with the value a customer gets, such as subscribers, campaigns or tenants, rather than a flat fee.
Human in the loop
Keep a person able to review, correct or hand off work at the points where automation or a single user can get stuck.
Message match
The screen people land on should repeat the promise of the ad, link or promo that brought them there.
Voice and personality
Write interface copy in a consistent, recognizable voice that fits the brand, and adjust its tone to the user's situation.
Dark patterns
Interface designs that trick, pressure or obstruct users into choices that benefit the company and that they would not otherwise make.
Fake door test
Show an entry point for a feature that does not exist yet and measure how many people try it, to test demand before building.
Positive friction
A small, deliberate pause or extra step placed where a fast, automatic choice would hurt the user or the product.