# llms.txt for www.ntp-tester.eu
# RDEM Systems - NTP Live Measurement

> Live browser-based NTP measurement: jitter, clock offset, network latency and round-trip delay against Stratum 1 GNSS references. Sub-millisecond precision, no install, dedicated analysis pages for each metric. Available in English and French.

## Main Pages

- [Home — NTP Jitter, Offset & Latency Tester](https://www.ntp-tester.eu/): Live browser-based measurement tool with real-time offset and latency display
- [Jitter Analysis](https://www.ntp-tester.eu/jitter-analysis.html): What NTP jitter measures, acceptable thresholds by network type, CLI and browser measurement methodology
- [Live NTP Offset](https://www.ntp-tester.eu/offset-live.html): Clock offset measurement, positive vs negative interpretation, thresholds by use-case, HTTPS measurement method
- [NTP Latency Benchmark](https://www.ntp-tester.eu/latency-benchmark.html): Round-trip delay, acceptable RTD by geographic distance, comparison of common EU NTP sources
- [How NTP Works](https://www.ntp-tester.eu/how-ntp-works.html): Simple explanation of the NTP protocol in 5 minutes
- [Why PCs Lose Time](https://www.ntp-tester.eu/why-pc-loses-time.html): Clock drift causes and fixes on Windows, Mac, Linux
- [CLI Commands](https://www.ntp-tester.eu/cli-test.html): ntpq, chronyc, timedatectl reference
- [NTS Security](https://www.ntp-tester.eu/nts.html): Network Time Security explained

## French Version

- [Accueil — Mesure Jitter, Offset & Latence](https://www.ntp-tester.eu/fr/): Outil de mesure en direct dans le navigateur
- [Analyse du Jitter](https://www.ntp-tester.eu/fr/analyse-jitter.html): Seuils, causes et mesure du jitter NTP
- [Offset NTP en Direct](https://www.ntp-tester.eu/fr/offset-direct.html): Mesure et interprétation du décalage d'horloge en temps réel
- [Benchmark de Latence NTP](https://www.ntp-tester.eu/fr/benchmark-latence.html): Délai aller-retour et comparatif des sources EU
- [Comment fonctionne NTP](https://www.ntp-tester.eu/fr/comment-fonctionne-ntp.html): Explication simple du protocole NTP
- [Pourquoi les PC perdent l'heure](https://www.ntp-tester.eu/fr/pourquoi-pc-perd-heure.html): Causes et correctifs de la dérive d'horloge
- [Commandes CLI](https://www.ntp-tester.eu/fr/commandes-cli.html): Référence ntpq, chronyc, timedatectl
- [Sécurité NTS](https://www.ntp-tester.eu/fr/nts.html): Network Time Security

## Topics Covered

- Live NTP jitter measurement and interpretation
- Real-time clock offset against Stratum 1 GNSS reference
- Round-trip delay and network latency benchmarking
- Clock drift detection across operating systems
- Browser-based measurement methodology (HTTPS over UDP constraints)
- Comparison of public EU NTP sources (ntp.rdem-systems.com, Cloudflare, PTB, Netnod, NIST, pool.ntp.org)
- Sign convention for NTP offset (positive = clock ahead, negative = behind)
- Jitter thresholds by network type (LAN, WAN, Wi-Fi, mobile)
- RTD budget and its impact on offset precision

## Related Sites (Same Authority — Specialised by Intent)

- [ntp.rdem-systems.com](https://ntp.rdem-systems.com/): Enterprise reference architecture (GPS, PPS, NTS, hyperviseurs, AD)
- [check-ntp.net](https://www.check-ntp.net/): Diagnostics and troubleshooting — firewall port 123, chrony vs ntpd, stratum-16 recovery (not measurement)
- [online-ntp-validator.com](https://www.online-ntp-validator.com/): Compliance audit — NIS 2, ISO 27001, PCI-DSS, DORA, RFC 1918 internal-server validation (not measurement)

## Author

Richard Demongeot
https://www.demongeot.biz/

## Provider

RDEM Systems SAS
https://www.rdem-systems.com/