Two of the country’s largest internet service providers are going to court over the definition of “fiber.”

AT&T filed a lawsuit against Charter on Friday, alleging that its marketing of “fiber-powered” internet is misleading customers. The argument centers around an ad campaign from Charter, which sells home internet under the brand name Spectrum. 

Fiber is widely considered the gold standard for home internet. Fiber used to be the only connection type capable of delivering symmetrical upload and download speeds, but the latest DOCSIS 4.0 technology allows cable providers to transmit symmetrical speeds after upgrading their networks. On Spectrum’s cable plans, typical upload speeds top out at 40Mbps, while download speeds exceed 1,000Mbps. I always advise readers to go with a fiber provider whenever it’s available. 

Over the past couple of years, cable internet providers have increasingly tried to capitalize on that fiber cache. It’s technically true that Spectrum provides “fiber-powered” internet. Like all cable ISPs, Spectrum uses fiber-optic cables — thin glass strands that carry data through light signals — for the vast majority of its network. But it switches to copper coaxial cables in most cases to travel the proverbial last mile to your home. Fiber providers like AT&T, on the other hand, run the fiber connection all the way to the jack in your wall. 

Many cable companies are in the process of upgrading that last mile to fiber. Spectrum currently reports to the Federal Communications Commission that 2.3% of US households have access to its fiber plans, while 29.9% can get its cable plans. 

“We don’t think customers should have to be telecom experts or squint at the fine print to know what they’re buying,” an AT&T representative told me in an email. “When internet is marketed as fiber, customers deserve 100% fiber all the way to their home.”

I spot-checked a handful of addresses on Spectrum’s website in Dallas, where AT&T is filing its lawsuit, and some of them did return fiber plans. According to FCC data, which is self-reported by ISPs, Spectrum covers around 608,000 households in Dallas, while AT&T covers almost 495,000. 

This isn’t the first time Charter has been chided for passing itself off as a fiber provider. In March, Spectrum agreed to modify its “fiber-powered” statements after AT&T brought a challenge through the BBB National Programs’ National Advertising Division.

Spectrum’s advertising describes its service as “fiber-powered” but notes in the fine print that it’s connected via coaxial lines.Spectrum/Screenshot by CNET

As a part of that challenge, Spectrum agreed to “clearly and conspicuously” disclose that its “fiber-powered internet services are not delivered to customers’ homes over a fiber-to-the-home infrastructure.” The fine print on Spectrum’s internet page notes that the connection to the premises is delivered via coaxial lines.

Charter did not respond to a request for comment. 

Joe Supan is a senior writer for CNET covering home technology, broadband, and moving. Prior to joining CNET, Joe led MyMove's moving coverage and reported on broadband policy, the digital divide, and privacy issues for the broadband marketplace Allconnect. He has been featured as a guest columnist on Broadband Breakfast, and his work has been referenced by the Los Angeles Times, Forbes, National Geographic, Yahoo! Finance and more. See full bio