Question 1

What is NTP jitter and what value is acceptable?

Accepted Answer

NTP jitter is the variation (standard deviation) of offset measurements between a client and its time source over a short window. On a wired LAN, expect jitter below 1 ms; on a stable home broadband link, below 5 ms; on congested or Wi-Fi paths, 10–30 ms is common. Jitter above 50 ms typically indicates a problematic path or a source under load. Our live tester shows jitter in real time alongside offset and round-trip delay.

Question 2

How do I measure live NTP offset from the browser?

Accepted Answer

This tester fetches a high-precision timestamp from an RDEM Systems Stratum 1 GNSS reference via HTTPS, estimates the one-way latency as half the round-trip, and computes the offset between your browser clock and the authoritative source. A value below 100 ms is excellent, 100–1000 ms is acceptable but worth checking, and above 1 s indicates a broken NTP service. The measurement refreshes every 10 seconds to expose drift.

Question 3

What does NTP round-trip delay (RTD) tell me?

Accepted Answer

Round-trip delay is the elapsed time between sending the NTP request and receiving the response. It bounds the worst-case offset uncertainty: the NTP algorithm assumes one-way latency is roughly RTD/2, so a high RTD reduces the precision of the offset estimate. For accurate clocks, prefer sources with stable, low RTD over distant sources with variable delay.

Question 4

How do I benchmark NTP latency across multiple servers?

Accepted Answer

The simplest CLI method is 'chronyc sourcestats' (Linux) which shows offset, frequency, skew, standard deviation and measurement count per source. For one-shot probing, 'ntpdate -q ' or 'sntp ' print a single offset and delay measurement. From the browser, this tester exposes the round-trip delay for its own Stratum 1 reference — compare against ping to identify NTP-specific path quality.

Question 5

Why does my PC clock drift even with NTP enabled?

Accepted Answer

Between synchronisations, the system clock runs on the CPU crystal whose frequency varies with temperature (typically ±10 ppm → ~1 s / day). NTP corrects this drift at each poll. If drift is visible, the poll interval is too long, the source is unreliable, or NTP was interrupted (sleep/hibernate, network lost). Check continuous sync with our live offset display — stable < 100 ms confirms NTP is actually working.

NTP Jitter, Offset & Latency Tester

Real-Time Synchronization Test

🖥️ Your System

🌐 NTP Reference

What This Tester Measures

📊 NTP Jitter

⏱️ Live Clock Offset

🌐 Round-Trip Delay

🕰️ Clock Drift Detection

High-Precision NTP for Production

Is Your NTP Secure?