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A slow speed test cannot tell you whether a subsea cable is damaged. First compare Wi-Fi with a wired Ethernet connection, check whether multiple devices and destinations are affected, and look for a matching notice from your ISP or a public outage tracker. Those checks can narrow the likely cause; only an authoritative report can confirm a cable fault.
Start by checking how widespread the slowdown is
Note when the problem began, whether it is continuous or intermittent, and which devices and services are affected. Try several destinations, including a local service and an international website or service.
- If one device or application is slow while others work normally, an issue with that device, app, or service is more likely than a widespread international capacity problem.
- If several devices and different destinations are affected, the cause may be in your home network, with your ISP, or farther along the route. That pattern alone does not identify a cable.
Compare Wi-Fi with Ethernet
If you can, connect a computer to your router with Ethernet. Pause large downloads and disconnect any VPN for a controlled comparison, then run the same test on Wi-Fi and Ethernet using the same test service and, if available, the same selected server. Cloudflare describes speed.cloudflare.com as a way to test an individual connection’s performance and quality. Its Internet Quality guidance also notes that erratic in-home Wi-Fi can reduce measured speeds below the subscribed service level. [c002]
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Outbyte PC Repair FREERepair Windows errors before they cause bigger problemsFix Now →Outbyte Driver Updater FREEScan for outdated or missing drivers - takes under a minuteDriver Scan →- A noticeable improvement over Ethernet points toward the local Wi-Fi connection as a contributor.
- A similar slowdown over Wi-Fi and Ethernet makes Wi-Fi alone less likely, but does not distinguish an ISP problem from an international routing issue or a cable outage.
Ethernet is a comparison, not a fix for congestion beyond your home. Use a cable only if your computer and router have compatible Ethernet ports.
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Check your ISP and public outage information
Look for an ISP notice
Check your ISP’s service-status page, app, or announcements for an issue affecting your location or network. A notice that matches your symptoms and start time is more relevant than a general report about another provider or country.
Check Cloudflare Radar’s Outage Center
Look for the affected country, region, or network in Cloudflare Radar’s Outage Center. Its event information can include location, affected autonomous system number (ASN), outage scope, likely cause, and start and end times. Cloudflare says the cause field reflects publicly available information; an outage may stem from cable damage, power loss, severe weather, filtering or blocking, or a government-directed shutdown. An outage listing therefore does not automatically mean a subsea cable is involved. [c001][c003]
Cloudflare curates observed disruptions when it can correlate traffic drops with context such as ISP communications or reporting. Events may be partial or complete, and some have no sourced likely cause. A missing listing does not rule out a problem affecting your household or network. Radar describes network- or location-level evidence; it cannot establish that every customer on a network is affected. [c004]
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Incident status and restoration estimates can change. For example, Cloudflare Status attributed congestion between its Tokyo and Singapore data centers to multiple subsea outages that began September 21, 2026, and marked that incident resolved on September 29, 2026. That is a dated example, not evidence about a current slowdown; check live notices for the period you are investigating. [c006]
Use speed tests and routes as clues, not proof
A speed-test result is a symptom, not a diagnosis. It can be affected by Wi-Fi quality, device limits, the test server’s location, congestion, or the route to the destination. A test to one server may not reflect how another website or service performs.
If you are comfortable with network tools, run traceroute (called tracert on some systems) to more than one destination and save the output with the time and destination. A distributed traceroute may help show whether paths from other networks differ. Latency, packet loss, and route changes can give an ISP useful investigative clues, but routers may suppress or deprioritize probe replies, and Internet routes can change for routine operational reasons. A changed route or higher latency does not identify a specific cable. Cloudflare recommends collecting traceroute output and, where useful, distributed traceroutes as supporting information for troubleshooting. [c005]
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Submarine Cable Status offers a useful distinction in its reporting vocabulary: “Confirmed” means an owner, operator, consortium, or other authoritative party has reported a fault; “Suspected” means different independent signals agree without authoritative confirmation; and “Observed” means measurements look abnormal. Its methodology warns, “Traffic can reroute for many reasons, so an anomaly is never proof of a cable fault.” This is a cautious model for describing evidence, not a substitute for an operator or ISP confirmation. [c006]
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Choose wording that matches the evidence
| What you can say | What supports it |
|---|---|
| Confirmed cable fault | An authoritative statement from a cable owner or operator, consortium, ISP, regulator, or relevant status notice confirms cable damage or an outage. |
| Suspected, or consistent with a reported outage | Several independent clues align, such as an operator report, a network-level performance change, and route or latency observations, but no authoritative cable statement confirms the fault. |
| Observed slowdown; cause unknown | Your measurements show slower performance, but there is no reliable evidence identifying the cause. |
Cloudflare’s Q3 2025 outage review described a specific case in which UAE provider du warned of slowness due to an international subsea cable cut. For du’s network during the cited September 6, 2025 period, Cloudflare Radar metrics showed median bandwidth falling from 25 Mbps to as low as 9.8 Mbps, while median latency rose from 30 ms to over 60 ms. Those network- and time-specific measurements illustrate corroboration; they are not a threshold for diagnosing an individual home connection. [c007]
A separate historical example shows why impact can vary by place and provider. The Internet Society’s July 2024 report on the East Africa outage says Cloudflare and Kentik analyses identified Tanzania as having the greatest reduction in performance during the May 12 event. That finding describes that incident, not the expected impact of another outage. [c008]
There is no universal home-user speed, latency, or packet-loss cutoff that proves a subsea cable fault. Treat measurements as evidence to share, not as a cable diagnosis.
Give your ISP a useful evidence trail
If the slowdown persists, contact your ISP and provide:
- The date and exact time the problem began, including your time zone.
- Whether it is continuous or intermittent.
- The affected devices and websites or services, plus any destinations or test servers you checked.
- Your Wi-Fi and Ethernet results, noting whether you used the same test service and server.
- Traceroute output and its destination and timestamp, if available.
- Any matching ISP notice or public outage record you found.
Cloudflare’s troubleshooting guidance also recommends giving support timestamps, symptom details, and relevant route information. [c005]
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