Net Promoter Score (NPS) measures customer loyalty by asking a single question: “How likely are you to recommend [our business] to a friend or colleague?” on a 0–10 scale. Responses of 9–10 are Promoters, 7–8 are Passives, and 0–6 are Detractors. The score is Promoters % minus Detractors %, yielding a number from -100 to +100.
For customer portal contexts, NPS is the headline customer satisfaction metric. It correlates with retention and growth, but it’s a lagging indicator — by the time NPS drops, customers are already disengaging. Pair NPS with leading indicators like CES (effort score), portal adoption, and feature usage.