2020 has been good to Roku (NASDAQ:ROKU). The company's year-over-year growth rate in active accounts -- arguably Roku's most important metric -- accelerated throughout the year as consumers have been sheltering at home and are turning to the leading smart TV operating system.

Furthermore, the secular tailwinds of TV watchers ditching traditional television in exchange for streaming TV (and the subsequent shift in TV marketing budgets) is fueling Roku's strong momentum.

But these are still early days for the company. In fact, there's good reason to believe 2021 may be a particularly good year for its business.

Let me explain: Below are three catalysts for Roku in 2021 and beyond.

A person looking at a laptop, next to the number 2021.

Image source: Getty Images.

1. A reacceleration in ad spend

Sure, Roku's active-account growth has accelerated in 2020. But growth in the company's average revenue per user (ARPU) has decelerated.

In 2019, ARPU was $23.14, up 29% year over year. But as the pandemic hit and many businesses' operations were hurt, advertising spend contracted, negatively affecting Roku's ARPU metric. By the third quarter of 2020, trailing-12-month ARPU growth had decelerated to 20%. 

Highlighting the slowdown in ad spend, monetized video ad impressions on the Roku platform were more than doubling on a year-over-year basis every quarter leading up to the pandemic. In the second quarter of 2020, however, this growth rate was just 50%. This contraction in ad spend was evident across all digital advertising companies.

As businesses have adapted to these new and ever-evolving conditions, ad budgets are ramping back up again. Monetized video ad impressions on Roku's platform grew 90% year over year in the third quarter. As marketers' budgets improve, Roku is well positioned to benefit.

2. The Roku Channel

One often overlooked catalyst for Roku is the company's Roku Channel, an app that aggregates third-party content and streaming services into a user-friendly format. The app is winning over streaming services, advertisers, and TV watchers.

Roku Channel displayed on a TV

The Roku Channel. Image source: Roku.

Available on Android, iOS, and Fire TV, the Roku Channel takes Roku's expansive partnerships with marketers and streaming services beyond the Roku platform. The Roku Channel now reaches 54 million people, a number that is notably greater than the Roku platform's 46 million active accounts. Even more, Roku said streaming hours on the Roku Channel increased at a faster rate on a year-over-year basis than for any other app on its platform.

While Roku takes its own cut on the economics of the Roku Channel, the company believes its content partners are seeing monetization benefits as well.

"As we continue to offer users more content and features in The Roku Channel," management said in its third-quarter shareholder letter, "we believe our viewers will stream more content from within it and it will become an even more important source of economics to our content partners."

3. New streaming services

For Roku shareholders, there's no need to pick which streaming service will be the most successful. Investors benefit from the economics of every streaming service on the company's platform.

This is particularly exciting during a time when all content owners are doubling down on streaming services. Comcast, for instance, launched a new service called Peacock in April, and ATT's WarnerMedia launched HBOMax in May. Both services are now available on Roku.

In 2021, media giants will likely continue building out their streaming plans -- plans that will often involve Roku on some level.

While it's impossible to know where Roku stock will trade in the near term, these three catalysts for its business paint a rosy outlook for the growth stock over the long haul.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.