Redbox Instant by Verizon appears to be growing. But Outerwall, the parent company for Redbox and partner with Verizon in the joint venture behind the subscription rental service, won't say by how much.

The Outerwall Inc. executive team says it isn't ready to disclose subscriber numbers or revenue gains just yet. However, Outerwall did say in its earnings call late Thursday that it will work closely with Verizon Communications Inc. (NYSE: VZ) to figure out how best to disclose more details as the service matures.

Although it didn't share much data, Outerwall did report that Redbox Instant continued to add new customers throughout 2013. Overall rental transactions rose, and average streaming times increased each month.

In addition, company executives took pains to point out that Redbox Instant has expanded to more devices faster than its competitors. In the fourth quarter, the streaming service launched on Xbox One, PS3 and PS4, Kindle Fire, and Windows 8. It's also available on the Xbox 360, iPhones and iPads, Android phones and tablets, Roku boxes, Google TV, Samsung smart TVs and Blu-ray players, and LG smart TVs.

While there are positive signs for Redbox Instant, the service still faces an uphill battle against such online video market leaders as Netflix Inc. (Nasdaq: NFLX) and Amazon.com Inc. (Nasdaq: AMZN). For $8 per month, Redbox offers subscribers streaming access to its online video library, along with four credits toward DVD rentals at Redbox kiosks. However, while Netflix and Amazon include TV show episodes and original content in their catalogs, Redbox offers just movies and video games. (See Verizon/Redbox Take a Swing at Netflix.)

— Mari Silbey, special to Light Reading