Public NTP Server List

This page provides a short list of recognizable Network Time Protocol (NTP) service hostnames. It replaces the previous unverified dump of hundreds of third-party servers. SoupCalc does not operate these services, test their live status, or promise their availability.

Use a hostname, not an IP address copied from a DNS lookup. Providers and pools can change the addresses behind their names.

How to use the list

Choose a service that your operating system, device vendor, or network policy supports. Enter its hostname in the device's NTP or Internet Time setting. Traditional NTP normally uses UDP port 123, so a firewall that blocks that traffic can prevent synchronization.

For NTP Pool, the project recommends numbered names such as 0.pool.ntp.org through 3.pool.ntp.org for an ntpd configuration. Those names resolve to changing sets of volunteer servers. Large deployments and products should follow the pool's vendor terms rather than sending every device to the generic pool name.

Google Public NTP uses a leap-smear policy around leap seconds. Google specifically warns against mixing its smeared time with non-smeared NTP sources in one client configuration. Check the selected provider's leap-second behavior and keep the sources in one client compatible.

Worked example

For a small Linux machine using chrony, an administrator might add a provider hostname to the system configuration:

server time.cloudflare.com iburst

After restarting or reloading the time service, inspect its source status with the operating system's supported command, such as chronyc sources -v. A configured hostname alone is not proof that the clock is synchronized: verify reachability, selected source, offset, and service state.

If policy calls for the NTP Pool instead, use the pool's documented numbered hostnames rather than copying a temporary resolved IP address.

Limits and operational cautions

• Public endpoints have different terms, architectures, monitoring, and leap-second policies. Review the provider documentation before production use.
• Do not mix leap-smear and ordinary UTC sources unless your time software and policy explicitly support that design.
• A browser page cannot determine the NTP status of your device; browsers normally cannot send arbitrary UDP NTP queries.
• NTP synchronizes time, not time-zone display. Configure the operating system time zone separately.
• Volunteer public pools are not a substitute for a designed redundant time architecture where incorrect time could affect safety, authentication, databases, financial records, or regulated systems.
• Use internal time servers, authenticated mechanisms, or vendor-supported infrastructure when your threat model requires them. The public NTP Pool does not provide NTP authentication.

Sources

• NTP Pool Project — How to use the pool
• Google Public NTP FAQ
• Cloudflare Time Services — NTP usage
• NIST — Internet Time Service
• NIST — Internet Time Service firewall information

Editorial record

Written and manually reviewed by the SoupCalc Editorial Team. The visible hostname table was checked against the current tool and the linked provider documentation. Last reviewed: August 10, 2026. Live availability is not continuously monitored. This page remains unavailable for indexing and advertising until all approved localizations pass review.