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Technology Types

DSL (Digital Subscriber Line)

Internet service delivered over traditional copper telephone lines, with speeds that degrade significantly over distance from the provider's central office.

What It Means

DSL was the dominant U.S. broadband technology through the mid-2000s and is now widely considered legacy infrastructure. The technology modulates data onto the same copper twisted-pair lines originally installed for voice telephone service, meaning DSL availability roughly tracks the Bell System footprint established before the 1984 breakup of AT&T. ADSL (Asymmetric DSL) typically delivers 1 to 25 Mbps download and 0.5 to 3 Mbps upload. ADSL2+ extends this to 25 Mbps, and VDSL (Very-high-bit-rate DSL) can reach 50 to 100 Mbps within roughly 3,000 feet of a central office or remote terminal, falling off sharply with distance. Because distance is the primary bottleneck, rural DSL customers often receive 3 to 6 Mbps even when urban customers on the same provider receive 50 Mbps. The FCC raised the broadband definition to 100 Mbps download and 20 Mbps upload in March 2024, which means most ADSL connections no longer legally qualify as broadband. AT&T announced in 2020 that it would stop selling new standalone DSL to new customers, shifting its capex toward AT&T Fiber and fixed wireless. Frontier, CenturyLink (now Lumen), and Windstream still sell legacy DSL in areas not yet overbuilt with fiber, and millions of BEAD-eligible locations remain DSL-only. In the Broadband Grade, DSL-only ZIP codes are penalized in both the download speed category (40% of grade) and the fiber availability category (20% of grade), typically producing C, D, or F grades.

Frequently Asked Questions

What does "DSL" mean?

Internet service delivered over traditional copper telephone lines, with speeds that degrade significantly over distance from the provider's central office.

Why does DSL matter for internet quality?

DSL was the dominant U.S. broadband technology through the mid-2000s and is now widely considered legacy infrastructure. The technology modulates data onto the same copper twisted-pair lines originally installed for voice telephone service, meaning DSL availability roughly tracks the Bell System foo...

Related Terms

Fiber Optic (FTTH)
Internet delivered via glass or plastic strands that transmit data as pulses of light, offering the fastest and most reliable residential connections available.
Cable Internet (DOCSIS)
Broadband delivered over coaxial cable TV lines using the DOCSIS protocol, typically offering 100-1,200 Mbps download but significantly slower upload speeds.
Fixed Wireless Access (FWA)
Broadband delivered wirelessly from a cell tower or base station to an antenna at the customer's location, using 4G LTE or 5G signals.
Satellite Internet
Broadband delivered via orbiting satellites, available nearly anywhere but historically limited by high latency and low speeds until the introduction of low-earth orbit constellations.

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About This Data

Definitions based on FCC standards, industry specifications, and federal broadband policy. Speed benchmarks reflect 2024 FCC standards. See our methodology.

this entity is one of the U.S. internet availability and broadband speed concepts that recurs across this site. The definition above is the technical answer; the paragraphs below add the practical context for how the concept connects to the the FCC Broadband Data Collection (BDC) data behind every per-entity page on the site.

In the the FCC Broadband Data Collection (BDC) data, this concept shapes one or more of the fields that drive the per-entity grades and rankings on this site. The methodology page describes which fields feed into which output; this glossary entry documents the underlying term.

Source: FCC Broadband Data Collection, 2026.