PostgreSQL EXPLAIN Analyzer

EXPLAIN shows the query planner's execution plan — the strategy PostgreSQL will use to execute your query. EXPLAIN ANALYZE actually runs the query and shows real timing and row counts alongside the estimates. Always use EXPLAIN ANALYZE for performance tuning.

Cost is a unitless estimate based on disk I/O and CPU operations. It has two parts: startup cost (work before the first row is returned) and total cost (work to return all rows). Lower total cost generally means a faster query, but cost doesn't map directly to milliseconds.

A Sequential Scan reads every row in a table from start to finish. It's fast for small tables or when you need most rows, but slow on large tables with selective WHERE filters. The analyzer will flag Seq Scans on tables with many estimated rows and suggest adding an index.

Index Scan follows the index to find matching rows, then fetches those rows from the heap (table storage). Index Only Scan returns all needed data directly from the index without touching the heap — much faster when your query only needs indexed columns.

Nodes are colored by their percentage of the maximum cost in the plan. Red nodes (>70%) are your biggest bottlenecks. Common causes: missing indexes, large sequential scans, expensive sorts, or nested loops on large datasets.

No. This tool runs entirely in your browser. Your SQL queries and query plans never leave your machine.