Operator
Good morning, and welcome to the QTS Realty Trust First Quarter 2021 Earnings Conference Call. [Operator Instructions]
I would now like to turn the conference over to Stephen Douglas, Head of Investor Relations at QTS. Please go ahead, sir.
Stephen Douglas
Executive Vice President of Finance
Thank you, operator. Hello, everyone, and welcome to QTS First Quarter 2021 Earnings Conference Call. I m Stephen Douglas, Head of Investor Relations at QTS, and I m joined today by Chad Williams, our Chairman and Chief Executive Officer; and Jeff Berson, our Chief Financial Officer. We also are joined by additional members of our executive team who will participate in Q&A. Our earnings release and supplemental financial information are posted in the Investor Relations section of our website. We also provided slides and made them available with the webcast and on our website to make it easier to follow our presentation today.
Mobility and WarnerMedia were the stars of AT&T Q1 22 APR 2021
AT&T maintained earnings guidance for the year after an opening quarter in which its Mobility and WarnerMedia units proved highlights.
On an earnings call, the US operator credited higher equipment sales for a rise in revenue at its Mobility unit, up 9.4 per cent year-on-year to $19 billion, while subscription growth fuelled by its HBO and HBO Max services contributed to a 9.8 per cent increase for WarnerMedia to $8.5 billion.
AT&T highlighted ongoing efforts to reduce its debt levels, with management stating it would continue to shed select assets as part of its strategy.
Operator
Good day, everyone, and welcome to the Crown Castle Q1 2021 Earnings Call. [Operator Instructions] At this time, I d like to turn the conference over to Ben Lowe. Please go ahead.
Benjamin Raymond Lowe
Vice President Of Corporate Finance & Treasurer
Great. Thank you, Vicki, and good morning, everyone. Thank you for joining us today, as we discuss our first quarter 2021 results. With me on a call this morning are Jay Brown, Crown Castle s Chief Executive Officer; and Dan Schlanger, Crown Castle s Chief Financial Officer. To aid the discussion, we have posted supplemental materials in the Investors section of our website at crowncastle.com, that will be referenced throughout the call this morning. This conference call will contain forward-looking statements, which are subject to certain risks, uncertainties and assumptions, and the actual results may vary materially from those expected.
Operator
Hello, ladies and gentlemen, thank you for standing by for GDS Holdings Limited s Fourth Quarter and Full Year 2020 Earnings Conference Call. [Operator Instructions]. After management s prepared remarks, there will be a question-and-answer session. [Operator Instructions].
I ll now turn the call over to your host, Ms. Laura Chen, Head of Investor Relations for the company. Please go ahead, Laura.
Laura Chen
Head of Investor Relations
Thank you. Hello, everyone. Welcome to 4Q and full year 20 earnings conference call of GDS Holdings Limited. The company s results were issued via Newswire services earlier today and are posted online. A summary presentation, which we will refer to during this conference call can be viewed and downloaded from our IR website at investors.gds-services.com.