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NTP Jitter, Offset & Latency Tester

Live clock measurement against Stratum 1 GNSS — browser-based, sub-millisecond

Jitter Analysis → Live Offset → Latency Benchmark →

Real-Time Synchronization Test

Testing your system...

🖥️ Your System

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Local Time

🌐 NTP Reference

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Server Time

✓ Excellent Synchronization

Offset: 0ms | Latency: --ms

What This Tester Measures

📊 NTP Jitter

Standard deviation of offset over a short window — the signature of an unstable path or overloaded source. Read the analysis →

⏱️ Live Clock Offset

Real-time delta between your system clock and our Stratum 1 GNSS reference, refreshed every 10 seconds. Interpretation guide →

🌐 Round-Trip Delay

Network latency to the time source — bounds the precision of the offset estimate. Benchmark across servers →

🕰️ Clock Drift Detection

Watch the offset evolve across successive polls to expose frequency drift of the local crystal. Why PCs drift →

High-Precision NTP for Production

Eliminate network jitter and improve sync accuracy with our European Stratum 1 & 2 infrastructure.

Deploy Reliable NTP with RDEM Systems →

Operated over AS206014 for optimal routing

Is Your NTP Secure?

Classic NTP has zero authentication. NTS (Network Time Security) fixes that with TLS 1.3 cryptographic protection.

Learn About NTS →

Not here to measure? Use the right tool for your use-case:

Our infrastructure services — Beyond time synchronization, RDEM Systems also provides sauvegarde externalisée en datacenter français for business-critical data protection.

About ntp-tester.eu — A free NTP testing platform maintained by RDEM Systems. Tests run from our own AS206014 infrastructure, with time references secured via NTS and synchronized to Stratum 1 GNSS sources. Hosted on Proxmox VE clusters.
About the author

Frequently asked questions

What is NTP jitter and what value is acceptable?

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.

How do I measure live NTP offset from the browser?

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.

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

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.

How do I benchmark NTP latency across multiple servers?

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 <server>' or 'sntp <server>' 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.

Why does my PC clock drift even with NTP enabled?

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.