Quick answer
If wired or near-router tests are far below your plan speed on multiple devices, the ISP/modem path deserves attention. If near-router speed is good but rooms are slow, the router placement or Wi-Fi coverage is more likely.
Quick tools for this guide
Use these small checks to turn the article into a decision. They are not a full diagnosis, but they help you decide what to test next.
Speed pattern checker
Use the strongest test you can
Ethernet is the cleanest comparison because it removes Wi-Fi from the path. If Ethernet is not available, use a near-router Wi-Fi test as the next best signal.
Read the pattern
A router or Wi-Fi problem usually changes by location. An ISP or modem problem tends to affect every room and multiple devices, including wired tests.
- Good wired, bad Wi-Fi: router, coverage, or interference.
- Bad wired and bad Wi-Fi: provider, modem, cable, or provisioning.
- Good phone, bad laptop: device-specific or VPN/work-device issue.
What to tell support
If the evidence points upstream, write down plan speed, wired speed, near-router speed, devices tested, date/time, and whether multiple rooms are affected. That makes the ISP conversation more concrete.
What to check before you spend money
- Record plan speed.
- Run a near-router test.
- Run a wired test if possible.
- Test at least two devices.
- Note whether the issue affects every room.
What not to do yet
- Do not accuse the ISP of throttling based on one Wi-Fi test.
- Do not buy mesh before checking router-side speed.
- Do not ignore damaged cables, splitters, or loose coax connections.
Get a guided answer
The diagnosis compares your answers and test numbers against the rule engine, then gives the likely cause, confidence, first fixes, and what not to buy yet.
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