What it is
The default effect is our tendency to stick with whatever is already selected. In a well-known study, countries where organ donation was the default (opt-out) had far higher effective consent rates than countries where people had to opt in (Johnson and Goldstein, 2003).
How strong is the evidence?
Strong, with varying size. A meta-analysis across many studies found defaults reliably shift choices towards the default option, but the size of the effect varied a lot between studies and domains (Jachimowicz et al., 2019). Expect a default to matter; don’t expect a specific lift.
Why defaults work
- Effort: changing a choice takes a click, thinking, or both.
- Endorsement: people read a default as a recommendation.
- Reference point: the default becomes “normal”, and moving away from it feels like giving something up.
Examples
Ecommerce
- Honest: standard delivery pre-selected because most customers choose it; the cheapest option clearly visible.
- Honest: the size or variant the shopper looked at last kept selected.
- Manipulative: gift wrap, insurance or donations pre-added to the basket.
SaaS
- Honest: annual billing shown as the default with the monthly option equally easy to choose and both prices clear.
- Honest: sensible settings on by default during onboarding (for example, weekly summary emails that are easy to switch off).
- Manipulative: auto-renewal on a free trial that isn’t clearly stated; marketing consent boxes pre-ticked.
Ethics
Defaults are powerful because people don’t change them, which is exactly why they’re open to abuse. Pre-selection of things people didn’t ask for is a recognised deceptive pattern (Deceptive.design), and pre-ticked boxes don’t count as valid consent under EU rules (EDPB, 2020). Use defaults to save customers effort, never to make choices for them.
How to test it
- Hypothesis: “Because most subscribers pick monthly delivery after trying other frequencies, we believe pre-selecting the monthly option will increase subscription starts, because it matches what most people choose.”
- Primary metric: completed sign-ups or orders.
- Guardrails: cancellations, refunds and complaints in the following weeks, which show whether people felt pushed.
- Look later: defaults can raise starts and lower satisfaction. Check retention, not just the first conversion.
See it in practice in the case study on subscribe-and-save defaults.