Friction refers to everything that makes it harder for a visitor to complete the desired action. It is not just technical errors – friction is also created by an unnecessary form field, mandatory registration before purchase, having to search for information that should have been at hand, uncertainty about the shipping cost, or being unclear about what happens after submission. Each such point filters out some people, with the largest drop-off occurring just before the goal, where they have already invested time. Removing friction is the cheapest way to increase the conversion rate, because it does not require more traffic. The approach has two phases: first, data is used to identify the step with the largest drop-off, then session recordings and testing are used to find out what is stopping people there. A common mistake is removing friction where none exists.
See also: Form optimisation, Session recording, Abandoned cart.