ClickHouse is an open-source OLAP database management system made by ClickHouse, Inc. OLAP (online analytical processing) means queries that scan and aggregate large amounts of data for reports and dashboards, rather than small updates of single records. ClickHouse is column-oriented: it stores the values of each column together, so a query reads only the columns it needs and the data compresses well.
Users query it with SQL. It serves real-time analytics, observability (storing and searching logs, metrics and traces, with the ClickStack stack), data warehousing and machine learning, including vector search. It runs as a database server, as ClickHouse Local for queries on local files such as CSV and Parquet without a server, and as chDB, an in-process SQL engine with a Pandas-compatible API. More than 100 integrations cover data ingestion, visualization and language clients.
The database is free and open source under the Apache 2.0 license. ClickHouse Cloud, the hosted service on AWS, Google Cloud and Azure, bills compute and storage separately by use and scales to zero when idle.