Dépannage internet

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Pick the problem you are having and follow the steps in order. Each step includes the fix and, where useful, a one-click test to confirm it worked.

Vérification automatique rapide
InternetVérification…
LatenceVérification…
DNSVérification…
IPv6Vérification…

  1. Check the lights on your modem/router. A red or blinking "Internet", "WAN", "DSL" or "Online" light means the line itself is down.
  2. Power-cycle in the right order: unplug the modem and router, wait 30 seconds, plug in the modem first and wait until it is fully online (2–3 minutes), then the router.
  3. Check for an outage on your ISP's status page or app, ideally from your phone's mobile data.
  4. Check cables: reseat the coax, fibre or phone cable and the Ethernet cable between modem and router.
  5. Log in to the router (often 192.168.1.1 or 192.168.0.1) and see whether it has a WAN IP address. If its WAN address is blank or in 169.254.x.x, the ISP connection is down.
  6. If nothing helps, contact your ISP. Note which lights are on and that you already restarted the equipment.

  1. Test another device. If others work, the problem is this device; if none work, follow "No internet on any device".
  2. Check the IP address. An address starting with 169.254 means the device did not get one from the router (DHCP failure). Use the IP type checker if unsure.
  3. Forget and rejoin the network, re-entering the password.
  4. Renew the IP and reset the network stack on Windows (run as administrator): 
    ipconfig /release
ipconfig /renew
ipconfig /flushdns
netsh winsock reset
    then restart. On macOS: System Settings → Network → Wi-Fi → Details → TCP/IP → Renew DHCP Lease.
  5. Disable VPNs, proxies and security software temporarily.
  6. Hotel or café Wi-Fi? Open http://neverssl.com to trigger the sign-in page.

  1. Measure first: run our ping and jitter test, then a speed test, once on Wi-Fi and once wired if possible.
  2. Find the bandwidth hog: pause cloud backups, game updates, torrents and 4K streams on other devices.
  3. Improve Wi-Fi: move closer, use the 5 GHz or 6 GHz band, keep the router high and central, and change the channel if neighbours are crowding yours.
  4. Restart the router and update its firmware.
  5. Compare with your plan. If wired speeds are far below what you pay for at several times of day, contact your ISP.
  6. Old hardware: routers and adapters older than Wi-Fi 5 (802.11ac) often cap real-world speeds.

  1. Wired or wireless? If drops happen only on Wi-Fi, it is interference or range: change channel, move the router, or add a mesh node.
  2. Run a long ping to your router and to the internet at the same time (ping -t 192.168.1.1 and ping -t 1.1.1.1 on Windows). Losses to the router point at your Wi-Fi; losses only to the internet point at the ISP line. See how to use ping and traceroute.
  3. Check the modem log for repeated resyncs or "T3/T4 timeouts" (cable), which indicate a line fault only the ISP can fix.
  4. Disable power saving on the network adapter (Windows Device Manager → adapter → Power Management).
  5. Overheating: make sure the router has airflow.

  1. Is it down for everyone? Check with Is It Down?.
  2. Try a private window to rule out extensions and cached data, then clear the site's cookies.
  3. Flush DNS (ipconfig /flushdns) and compare DNS records with what your computer resolves using nslookup example.com.
  4. Certificate warnings? Check your device's date and time, then test the site with the SSL checker.
  5. Blocked by your network? Parental controls, school/work filters or ISP blocks can stop certain sites. Try mobile data to compare.

  1. Check the spelling and whether the domain still exists with WHOIS.
  2. Flush DNS caches: Windows ipconfig /flushdns; macOS sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder; Chrome chrome://net-internals/#dns.
  3. Switch to a public resolver such as 1.1.1.1 or 8.8.8.8 in your router or device settings.
  4. Recently changed DNS for your own site? Watch the DNS propagation checker, and test DNSSEC: a broken DNSSEC setup causes failures only on validating resolvers.

  1. Measure jitter and packet loss with the ping test. Jitter above about 30 ms or any packet loss causes stutter.
  2. Use Ethernet for consoles and PCs; Wi-Fi adds variable delay.
  3. Enable QoS / Smart Queue Management on the router to stop uploads from swamping your connection (bufferbloat).
  4. Choose nearby game servers, and avoid VPNs that route you far away.
  5. Strict or moderate NAT type? Check whether you are behind carrier-grade NAT and test forwarded ports with the port checker.

  1. Confirm your public IP on the What's My IP Number page. If it changes often, use dynamic DNS.
  2. Check for CGNAT: if the router's WAN address is in 100.64.0.0/10 or private space, inbound connections cannot reach you. Ask your ISP for a public IPv4 address, or use IPv6 or a tunnel/VPN service.
  3. Set up port forwarding to the device's fixed local IP, then confirm with the open port checker.
  4. Allow the port in the device's own firewall, and make sure the service is running.
  5. Prefer a VPN (such as WireGuard) over exposing cameras and NAS admin pages directly to the internet.

  1. Check the domain's mail servers with MX lookup.
  2. Validate SPF, DKIM and DMARC with the email authentication checker; missing records are the most common cause.
  3. Check the sending IP's reputation with the blacklist check and confirm it has valid reverse DNS.
  4. Read the bounce message: codes like 550 5.7.1 usually name the exact policy that rejected the mail.

Une méthode systématique pour résoudre les problèmes d'internet

La plupart des problèmes de connexion se règlent en partant du composant le plus proche et en remontant vers l'extérieur : votre appareil → votre Wi-Fi ou votre câble → votre routeur → votre modem et la ligne de votre fournisseur d'accès → l'internet au sens large → le site web lui-même. Tester chaque couche à tour de rôle vous indique exactement où cela casse, pour que vous répariez la bonne chose au lieu de deviner. La vérification rapide ci-dessus vous dit déjà si vous pouvez atteindre internet, si votre connexion est réactive, si le DNS fonctionne et si vous avez l'IPv6.

Les cinq commandes que tout dépanneur devrait connaître

CommandeCe qu'elle vous apprend
ipconfig /all · ip addrVotre IP locale, la passerelle (routeur) et les serveurs DNS.
ping 192.168.1.1Si votre appareil peut joindre le routeur.
ping 1.1.1.1Si vous pouvez joindre internet sans avoir besoin du DNS.
nslookup example.comSi la résolution DNS fonctionne.
tracert · tracerouteÀ quel endroit du chemin la connexion ralentit ou s'arrête.

Si ping 1.1.1.1 fonctionne mais que ping example.com échoue, vous avez un problème de DNS. Si le ping vers le routeur échoue, le problème se situe à l'intérieur de votre réseau domestique. Pour un guide détaillé, lisez Problèmes de connexion internet courants : comment les résoudre.

Questions fréquentes

Pourquoi redémarrer le routeur règle-t-il autant de problèmes ?

Cela efface les fuites de mémoire et les tables de connexions bloquées, renouvelle la connexion avec votre fournisseur d'accès et permet souvent d'obtenir une nouvelle adresse IP.

Comment savoir si mon fournisseur d'accès est en cause ?

Si un appareil branché directement sur le modem n'a toujours pas de connexion ou de très mauvaises performances après un redémarrage, et que les voyants d'état ou le journal du modem montrent des erreurs, la panne est du côté du fournisseur d'accès.

Mis à jour

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