The keenly awaited Snapper app for iPhone had 10,000 downloads in its first 48 hours, and was number one in the app store for free and travel apps in Wellington in that time.
As of Friday morning, the iOS app had more than 10,000 downloads, two days after its release at 10am on Wednesday.
The app finally allows iPhone users to top up their Snapper cards from their phones, something Android users had been able to do for several years.
Metlink general manager Scott Gallacher said Snapper's move into the iPhone market was a big step, giving all customers the option to top up on-the-go.
"We already offer android top ups so we now have a convenient service offering for most cellphone users," he said.
"The iPhone app strengthens our reload network, adding to Android users, Snapper Card reload kiosks and retail outlets throughout the region to ensure people can get easy access to top-up services.
He also said increasing the reload options would reduce cash transactions on the bus.
"They remain welcome, but expanding options for electronic payment lessens health and security risks," he said.
The app had undergone three months of testing after Apple recently opened up the software to allow developers to use the hardware.
Snapper chief executive Miki Szikszai said iPhone customers would be able to check the balance of their card, instantly top it up, see their transaction history and receive refunds.
"Basically it means they don't have to go anywhere to do anything, they can do it right from their phone wherever they are.
"This will mean a lot to Snapper card users, it's by far the number one requested feature for us to deliver."
Users simply needed to sign in to their existing Snapper account, and follow instructions to scan a Snapper card by holding it flat to the phone.