The year's top tech stock isn't Zoom — it's not even a cloud company

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Only one U.S. tech stock has outperformed Zoom this year, and there's a good chance you've never heard of it.

Shares of Digital Turbine, a 22-year-old mobile phone software provider based in Austin, Texas, have climbed 573% in 2020, topping Zoom's 487% gain, as of Tuesday's close. The company's market cap started the year at a little over $600 million. It's now $4.3 billion.

Here's how Digital Turbine's business works. The company's software gets pre-loaded onto Android phones sold by carriers like AT&T and Verizon. Developers such as game makers, digital music companies and even restaurants pay Digital Turbine for slots on the phone so their apps are automatically available to the consumer upon activation. Digital Turbine gets paid an average of about $3 per phone sold and remits $1.80, or 60% of the transaction, to the carrier.