Query an NTP time server and return the time offset relative to the local clock
• Server address：Enter the NTP server hostname or IP (e.g. pool.ntp.org, time.apple.com)
• What is checked：UDP port 123 connectivity, server timestamp read, clock offset calculation
• Offset meaning：Positive value means the server is ahead of local time; negative means behind
• Node selection：Optionally select specific nodes; all available nodes are used by default
An NTP test sends a UDP NTP request to the specified server on port 123, reads the server's current timestamp, and calculates the clock offset relative to the probe node's local clock. It confirms that the NTP server is reachable, responding to queries, and that its reported time is close to the reference.
Common uses include verifying that an NTP server is reachable before configuring it as a time source, diagnosing clock drift issues on servers by identifying large time offsets, confirming that a pool.ntp.org address resolves and responds correctly, and checking connectivity to an internal NTP server from an external probe.
A well-synchronized server should have an offset of a few milliseconds relative to a reference time source. Offsets above 100ms are unusual and may indicate a configuration problem or network latency. Offsets above 1 second will cause NTP synchronization to fail.
A positive offset means the NTP server's clock is ahead of the probe node's clock. A negative offset means it is behind. The absolute value of the offset is what matters for synchronization quality.
Accurate time is required for TLS certificate validation, log correlation, database transactions, distributed system coordination, and authentication protocols like Kerberos. A server with a badly drifted clock can cause authentication failures and data inconsistencies.
pool.ntp.org is the most widely used public NTP pool. Cloud providers offer their own NTP servers (time.cloudflare.com, time.apple.com, time.google.com). For low-latency synchronization, use a server in the same region.