Test your CenturyLink or Quantum Fiber speed now
Run the test below on a wired connection, then compare against the right benchmark: DSL plans against their line-dependent tier, Quantum Fiber against the symmetrical tier you pay for. Repeat at morning and evening — a CenturyLink speed test at two times of day tells you whether the issue is your line or the network.
CenturyLink and Quantum Fiber are two brands from the same company — Lumen Technologies — selling two very different kinds of internet. CenturyLink is the legacy copper/DSL service; Quantum Fiber is Lumen's modern fiber network. A CenturyLink speed test tells you which one you actually have and whether it performs the way it should.
CenturyLink plans: DSL vs Quantum Fiber
| Plan | Download | Upload | Price |
|---|---|---|---|
| CenturyLink DSL | Up to 100–140 Mbps (line-dependent) | Up to 10–20 Mbps | ~$55/mo |
| Quantum Fiber 200 | 200 Mbps | 200 Mbps | ~$50/mo |
| Quantum Fiber 500 | 500 Mbps | 500 Mbps | ~$75/mo |
| Quantum Fiber Gig (940) | 940 Mbps | 940 Mbps | ~$100/mo |
Plan lineup last reviewed Sep 2026 — shown as approximate; DSL speeds vary by distance from the terminal, and fiber pricing varies by market. Confirm on centurylink.com or quantumfiber.com.
DSL speed depends heavily on your distance from CenturyLink's equipment — neighbors on the same plan can see very different numbers. Fiber is consistent: a Quantum Fiber speed test over Ethernet should land within a few percent of the advertised tier at any hour.
How to run an accurate CenturyLink speed test
- Test wired. DSL lines are sensitive to in-home wiring; an Ethernet test isolates the line from Wi-Fi noise.
- Close everything. Pause streams, backups, and updates on all devices before testing.
- Test morning and evening. DSL slows with distance and line noise, not congestion — but evening tests still catch neighborhood-level issues on shared segments.
- Compare against the right product. If your address was upgraded from CenturyLink DSL to Quantum Fiber, make sure you're judging the result against the fiber tier you pay for.
Why CenturyLink DSL feels slow
Copper DSL degrades with distance: the farther your home is from the terminal, the slower the sync. Old in-home phone wiring, unfiltered devices on the line, and aging modems all drag speeds down further. If your CenturyLink speed test shows under half your plan rate on a wired test, ask Lumen to check line quality — and check whether Quantum Fiber has reached your street, since fiber removes every one of these variables.
CenturyLink speed test FAQ
Both are Lumen Technologies brands. CenturyLink is legacy DSL over copper phone lines; Quantum Fiber is fiber-optic service with symmetrical speeds. Same company, different technology — check which one serves your address.
It varies by line distance: homes near equipment can see up to 100–140 Mbps down, while distant lines may sync far lower. Only a wired test at your address tells you what your specific line delivers.