Check Your CenturyLink Internet Speed
Whether you’re on legacy CenturyLink DSL or the fiber service branded Quantum Fiber, this test checks your real download speed, upload speed, and ping against what your plan promises in less than a minute. If you’re not sure which one you have: Quantum Fiber is CenturyLink’s parent company’s fiber-optic brand, while “CenturyLink” typically refers to the older DSL network, though the two brands overlap and have shifted in recent years — more on that in Section 5.
🔍 Pro Tip: If you’re on Quantum Fiber, a wired result should land close to your plan speed. If you’re on legacy CenturyLink DSL, expect a wider gap between advertised and actual speeds, since DSL performance depends heavily on your distance from the nearest network equipment.
Understanding Your Speed Test Results
⬇️ Download Speed
Download speed is a measurement of how fast your device is receiving data from the internet. It affects how quickly a page loads, or a file is downloaded, and minimizes buffering while streaming video. On Quantum Fiber, current plans range from 200 Mbps up to 8,000 Mbps (8 Gig) in very limited markets, with 940 Mbps (roughly 1 Gig) being the most common top-tier offering. On legacy CenturyLink DSL, speeds are far more modest and heavily location-dependent, often well under 100 Mbps, and sometimes far less, depending on your distance from CenturyLink’s nearest network equipment.
⬆️ Upload Speed
Upload speed measures how fast data is sent from your device to a server on the internet. Video calls, large file uploads like videos and photos, and cloud backups perform best with a fast upload speed. Quantum Fiber plans, as with most fiber internet plans, are fully symmetrical, meaning upload matches the download speed, which is a significant advantage over cable internet. Legacy CenturyLink DSL upload speeds are much lower and asymmetrical, often a small fraction of the download number.
⚡ Ping Rate (Latency)
Latency is the round-trip delay between your device and a server; it’s a measurement, in milliseconds, of how responsive your internet connection is. Quantum Fiber posts latency competitive with any fiber connection, typically in the single digits to low teens on a wired connection. Legacy DSL latency is generally higher and more variable, depending on the line quality and distance from network equipment.
- Under 100 ms for browsing and streaming; Quantum Fiber comfortably clears this; most DSL connections do too
- Under 30 ms for competitive gaming; realistic on Quantum Fiber, less consistent on DSL
What Is a Good CenturyLink Speed?
| Household | Recommended Speed | Best-Fit Option |
| 1–2 light users (browsing, email, HD streaming) | 200 Mbps | Quantum Fiber 200 Mbps, where available |
| 3–4 users (4K streaming, gaming, work from home) | 500 Mbps – 940 Mbps | Quantum Fiber 500 Mbps or ~1 Gbps |
| 5+ users / heavy uploads, content creation | 2 Gig or higher | Quantum Fiber 2 Gbps, select markets |
Where Quantum Fiber isn’t available at an address, legacy CenturyLink DSL is often the only option in the footprint. In that case, the realistic guidance is simpler: get the fastest DSL tier available and set expectations around browsing, email, and standard-definition streaming rather than heavy multi-device use.
Comparing CenturyLink & Quantum Fiber Plans
| Plan | Technology | Download | Upload | Starting Price* |
| Quantum Fiber 200 | Fiber | 200 Mbps | 200 Mbps | ~$30–35/mo |
| Quantum Fiber 500 | Fiber | 500 Mbps | 500 Mbps | ~$45–50/mo |
| Quantum Fiber 940 | Fiber | 940 Mbps | 940 Mbps | ~$60–65/mo |
| Quantum Fiber 2 Gig | Fiber | 2,000 Mbps | 2,000 Mbps | ~$80/mo (select markets) |
| Quantum Fiber 8 Gig | Fiber | 8,000 Mbps | 8,000 Mbps | ~$150/mo (very limited availability) |
| CenturyLink DSL | DSL | Varies by address, often <100 Mbps | Well below download | Varies significantly by location |
*Pricing may include promotions and enrollment in Autopay and paperless billing. Plans, speeds and pricing are subject to change at any time. Current as of August 2026.
Untangling the Brand: CenturyLink, Quantum Fiber, Lumen, and Now AT&T
CenturyLink’s parent company rebranded to Lumen Technologies in 2020, though the CenturyLink brand continued for residential DSL and voice service. The same announcement introduced Quantum Fiber as Lumen’s dedicated fiber-optic brand for newer, fiber-served markets. So historically: Lumen is the parent, CenturyLink is the legacy DSL brand, and Quantum Fiber is the fiber brand. Three names, one company.
That structure has changed further. On February 2, 2026, AT&T closed a $5.75 billion acquisition of substantially all of Lumen’s mass-market fiber business: over 1 million fiber subscribers and more than 4 million fiber locations across states including Washington, Oregon, Idaho, Utah, Colorado, Nebraska, and Iowa. In practice, this means a meaningful share of former Quantum Fiber customers now fall under AT&T’s ownership, though AT&T has indicated no immediate changes to pricing or service are planned.
CenturyLink Advertised Plan Tiers (not measured)
| Service Plan / Tier | Advertised Speed (Download / Upload) |
| Fiber Gigabit | 940 / 940 Mbps |
| Fiber 500 | 500 / 500 Mbps |
| Fiber 200 | 200 / 200 Mbps |
| High-Speed DSL | 100 / 10–20 Mbps |
| Standard DSL | 40 / 5 Mbps |
| Legacy DSL | 10 / 1 Mbps |
What Internet Speed Do You Need?
0-50 Mbps
Great for individuals browsing the web, checking email, and using basic apps.
50-100 Mbps
Great for streaming videos, video calls, and light use on a few devices.
100-200 Mbps
Great for 4K streaming, online gaming, fast downloads, and multiple devices.
200+ Mbps
Great for large households, remote work, gaming, and streaming on many devices.
Troubleshooting Slow CenturyLink Speeds
If your CenturyLink or Quantum Fiber speed test results are consistently below your plan speed, work through these before contacting support.
- Confirm Which Service You Actually Have. Quantum Fiber and legacy CenturyLink DSL troubleshoot differently, so check your bill or account portal first if you’re not sure. Fiber connections terminate at an optical network terminal (ONT), not a modem; DSL runs over a phone line into a DSL modem/router.
- On DSL: Check Your Line and Distance From Equipment. DSL speed drops the farther you are from CenturyLink’s nearest network equipment. If your speeds have always been modest, that’s often the ceiling for your specific address rather than a fixable problem. A degraded phone line or old wiring can also reduce DSL speeds further.
- On Quantum Fiber: Check Router Placement and Equipment Age. Keep your router central and elevated, away from metal and thick walls. If you’re on a multi-gig plan, confirm your router supports a fast enough WAN connection to deliver those speeds to a single wired device.
- Test With a Wired Connection. Connect a device directly to your modem or router with Ethernet and disable Wi-Fi on that device before retesting. On fiber, a wired result should land close to your plan speed; on DSL, some gap from the advertised ceiling is more normal given the technology.
- Contact Support if Nothing Improves. Reach out directly since they can check for a line issue, equipment problem, or plan mismatch not visible from a speed test alone, and can confirm which brand (CenturyLink or Quantum Fiber, and now potentially AT&T) services your address.
Frequently Asked Questions: CenturyLink Speed Test
Is Quantum Fiber the same as CenturyLink?
They’re related but not identical. Quantum Fiber is the fiber-optic internet brand of Lumen Technologies, the company formerly known as CenturyLink. CenturyLink today generally refers to legacy DSL service from the same parent company, though some Quantum Fiber accounts have shifted to CenturyLink billing and branding depending on market. Check your bill or account portal if you’re unsure which one you actually have.
Who owns Quantum Fiber?
As of February 2, 2026, ownership depends heavily on location. AT&T closed a $5.75 billion acquisition of most of Lumen’s consumer fiber business, including over 1 million former Quantum Fiber subscribers across several states. Lumen Technologies retains ownership of the parts of the business not included in that sale. If you’re a Quantum Fiber customer, checking your billing details directly is the most reliable way to know which company currently serves your account.
Is Quantum Fiber good?
On the technical merits, yes: symmetrical upload and download speeds, no data caps, no annual contracts, and pricing that’s competitive with or better than comparable fiber internet plans from AT&T Fiber in overlapping markets. The bigger question for most people is availability, since fiber coverage is address-dependent and Quantum Fiber’s footprint, now split partly under AT&T ownership, is more limited than a nationwide cable provider’s.
Is Quantum Fiber down right now?
Check your account portal or contact support directly for real-time outage status in your area. If nothing is flagged there but your speed test results are still slow, the issue is more likely local, like your router, ONT, or in-home wiring, than a broader outage.
How do I test my CenturyLink or Quantum Fiber internet speed?
Run the CenturyLink speed test. It takes under a minute and you can reference our guide to understanding your speed test results for a full explanation of the numbers. On Quantum Fiber, expect your wired result to land close to your plan speed; on legacy DSL, some gap from the advertised number is typical given the technology and the variables that affect its actual speed.
Why is my CenturyLink internet so slow?
It depends on whether you’re on DSL or Quantum Fiber. On DSL, distance from CenturyLink’s network equipment is often the biggest factor and isn’t always fixable. On Quantum Fiber, a slow result more often points to your Wi-Fi setup or router than the fiber connection itself. Run a wired test to isolate the cause and check the usual causes of slow internet and for troubleshooting if the wired result is also low.
