API

ClickHouse exposes data through several wire protocols. Pick whichever fits your client best — they are layered on top of the same engine, with the same SQL surface.

Page	Endpoint	Best for
HTTP interface	TCP 8123 / 8443	Curl, custom clients, embedded UIs, wide compatibility.
Native TCP	TCP 9000 / 9440	Lowest latency and CPU. Used by clickhouse-client, JDBC, ODBC, and language drivers.
MySQL wire	TCP 9004	Reuse mysql and BI tools that speak MySQL.
Postgres wire	TCP 9005	Reuse psql, libpq, and tools that speak Postgres.
gRPC	TCP 9100	Streaming protobuf API for service-to-service integration.
Arrow Flight	TCP 9006	Apache Arrow Flight RPC; ideal for Polars/DuckDB/Spark integrations.

What is shared

Every protocol funnels into the same Context, picks up the user's profile and permissions, and runs the query through the same parser → analyzer → planner → processor pipeline. So:

• The SQL dialect is the same across all of them.
• Settings (SET ... / per-query overrides) work the same way.
• All protocols carry progress, logs, and profile events alongside the result, where the protocol allows.
• All protocols can return any format (HTTP picks per request; native picks at handshake).

Authentication

Protocol	Auth
HTTP	Authorization, X-ClickHouse-User/Key, basic auth, mTLS
Native TCP	Username + password, JWT, Kerberos, SSH key
MySQL	mysql_native_password, caching_sha2_password
Postgres	md5, scram-sha-256, cleartext
gRPC	Token via metadata, mTLS
Arrow Flight	Bearer token, mTLS

See Access control for the underlying auth machinery.

Compression

• HTTP: request body and response body can be gzip / zstd / br / deflate. Native ClickHouse compression for the streamed response is available via compress=1.
• Native TCP: network_compression_method — LZ4 (default) or ZSTD.
• gRPC / Arrow Flight: rely on transport compression.

See Compression.

Choosing a protocol

• Curl, fetch, language libraries you already have → HTTP.
• Maximum throughput, official drivers → Native TCP.
• Existing MySQL or Postgres tooling → the matching wire.
• Service mesh, streaming results, contracts you can version → gRPC.
• Arrow ecosystem → Arrow Flight.

Related pages

• Server protocols — how every endpoint is implemented.
• Client, Client library — the canonical native-TCP client.