Guide · Analytics
Five numbers that tell you whether search works.
Most teams track the number of searches. That number goes up when search is bad, because people retry. These are the metrics that move when search gets better.
The five metrics
Zero-result rate
Share of searches that found nothing. The fastest signal: typos, slang and missing synonyms show up here first.
Rescue rate
Of the queries that found nothing as typed, the share a rewrite rescued. Each response records the rescuing step.
Search conversion
Share of search sessions that end in a purchase. Requires sending conversion events with the visitor id.
Impression CTR
Clicks divided by results shown, not by searches. Searches ÷ clicks hides nine ignored results on every page.
nDCG on a golden set
A fixed list of queries with graded expected results, scored after every change. The only metric that doesn't depend on traffic.
How to read them together
Searches up, conversion flat
Usually a relevance problem: people retry. Check the zero-result and low-CTR queries.
Zero results down, CTR down
Rewrites are rescuing queries with weak matches. Review which ladder step fires most and add synonyms.
nDCG down after a change
The change hurt known-good queries. Roll it back or run it as an experiment first.