Port 13: Daytime
Port 13 is the Daytime Protocol, which returns the current date and time as human-readable text when a client connects. It predates NTP (port 123) and has been superseded by it for anything that needs accurate time.
TCP/UDPLegacy protocolsUnencrypted by defaultIANA assigned
| Port number | 13 |
|---|---|
| Service | Daytime Protocol |
| Protocol | TCP/UDP |
| Category | Legacy protocols |
| Default encryption | No |
Security note. Port 13 is not encrypted by default. Restrict it to trusted networks, or use an encrypted alternative where one exists, to avoid exposing credentials and data in transit.
Frequently asked questions
What is port 13 used for?
Port 13 is the Daytime Protocol, which returns the current date and time as human-readable text when a client connects. It predates NTP (port 123) and has been superseded by it for anything that needs accurate time.
Is port 13 TCP or UDP?
Port 13 (Daytime) uses TCP/UDP.
Is port 13 secure?
Port 13 is not encrypted by default. Where possible, use an encrypted alternative or tunnel it over TLS or a VPN.
Should I open port 13 on my firewall?
Only if you specifically need Daytime. Expose it to the smallest set of trusted sources, and never open database or Windows-service ports to the whole internet.