Port 1433 — Microsoft SQL Server TCP Port

Note: IANA has formally registered Microsoft SQL Server on TCP/UDP, but in real-world practice this service operates over TCP only — a formal registration on a transport doesn't guarantee the protocol is actually implemented or used over it. This page's Protocol field reflects genuine usage, not just the registry entry.

What port 1433 is used for

Default listener port for Microsoft SQL Server database connections from applications and administration tools.

Is port 1433 encrypted?

Supports TLS encryption for client connections, but it must be explicitly configured and enforced — an unconfigured server may accept unencrypted connections.

Firewall & exposure considerations

Should be firewalled to known application servers only, never exposed to the open internet — database ports are a common target for credential-stuffing and brute-force scanning, and a compromised database often exposes far more sensitive data than a compromised web server would.

Common questions about port 1433

What is the default port for SQL Server?

TCP 1433, for the default instance (the one installed without an instance name). Microsoft notes the port can be changed, so 1433 is a default rather than a guarantee. Two nearby ports are easy to confuse with it: UDP 1434 belongs to the SQL Server Browser service, and TCP 1434 is used by the Dedicated Admin Connection on the default instance.

What port does a named instance use?

By default a named instance uses a dynamic TCP port, determined when the Database Engine starts. Clients that connect by instance name ask the SQL Server Browser service on UDP 1434 which port the instance is using. An instance can also be configured to listen on a specific TCP port instead.

Should the SQL Server Browser service be left running?

Microsoft's guidance is that, for the most secure environment, you should leave the SQL Server Browser service stopped and configure clients to connect using the port number. It receives unauthenticated UDP requests, which is one reason it is not always turned on during setup, and using it requires opening UDP 1434 in the firewall.

Related ports

• MySQL (the equivalent for MySQL/MariaDB)
• PostgreSQL (the equivalent for Postgres)

References

• Microsoft SQL Server: Configure the Windows Firewall to Allow SQL Server Access
• IANA registration for port 1433
• Microsoft Learn: Configure Windows Firewall for Database Engine access
• Microsoft Learn: Connect to the Database Engine from another computer

Look up any other port

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Last reviewed: October 14, 2026. Data source: IANA Service Name and Transport Protocol Port Number Registry. Security and usage notes are this site's own editorial content, not official IANA data.