Netflix is taking on increasing amounts of debt to fund its $6 billion annual commitment to original programming.

SAN FRANCISCO — Netflix is sinking deeper into debt in its relentless pursuit of more viewers, leaving the company little margin for error as it tries to build the world’s biggest video subscription service.

The big burden that Netflix is shouldering hasn’t been a major concern on Wall Street so far, as CEO Reed Hastings’ strategy has been paying off.

The billions of dollars that Netflix has borrowed to pay for exclusive series such as “House of Cards,” “Stranger Things,” and “The Crown” has helped its service more than triple its global audience during the past four years — leaving it with 109 million subscribers worldwide through September.

That figure includes 5.3 million subscribers added during the July-September period, according to Netflix’s third-quarter earnings report released Monday. The growth exceeded management forecasts and analyst projections. Netflix’s stock increased 2 percent in extended trading.

But Netflix’s subscriber growth could slow if it can’t continue to win programming rights to hit TV series and movies, now that there are more competitors, including Apple, Amazon, Hulu and YouTube.

If that happens, there will be more attention on Netflix’s huge programming bills, and “then we could see an investor backlash,” CFRA Research analyst Tuna Amobi says. “But Netflix has been delivering great subscriber growth so far.”

Netflix’s long-term debt and other obligations totaled $21.9 billion as of Sept. 30, up from $16.8 billion at the same time last year.

For all of this year, Netflix has warned that its negative cash flow might be as high as $2.5 billion.

Despite the huge cash outflow, Netflix has remained profitable, under U.S. accounting rules. The company earned $130 million on $3 billion in revenue in its latest quarter.