Conversion
Goal completion
Also called goal hit.
Goal completion is one recorded instance of a goal. Ten completions means the goal fired ten times.
How it is measured
Each time the goal's event arrives, add one. The same person can complete a goal more than once unless you limit it.
Tarsier counts completion events as they arrive and divides by visitors for the rate.
Worked example
A summer-camp site records 142 goal completions for registration_submitted in one week but only 96 distinct registrations. Duplicates come from parents who refresh the thank-you page.
The developer fires the event only on the first load of the confirmation and the two counts match.
How it differs
A goal completion is a single count. A goal is the rule. A conversion is the business outcome. Conversion rate divides completions by a base.
Common errors
Counting refreshes. Counting test submissions. Ignoring that one visitor can complete twice. Mixing completions and conversions. Losing events to ad blockers.
In practice
Check completions against your real records once a month and fix any gap.