The city’s purple Metro card user will be able to put money on the cards through their mobile phones by the end of June through an app-based service.

SHANGHAI residents will be able to put money on their Metro cards through their mobile phones by the end of June, ending the inconvenience of having to refill them at subway stations or convenience stores.

The app-based service will first be available only on phones enabled with so-called “near-field communication,” or NFC, functions and only with purple Metro cards that are equipped with particular chips, according to Shanghai Public Transportation Card Co.

Company officials told Shanghai Daily they don’t have a figure on how many people may be eligible to use the new service. There are more than 50 million Metro cards in use, purple and others.

“It would save a lot trouble. Not only the queuing, but also the trouble to walk to the refilling spot,” said a passenger who is refilling in a Metro station.

The mobile app is a step on the way toward allowing all Metro users to simply tap their phones at fare turnstiles someday. Cardless transport is at its early stages. The Metro card company last year introduced NFC-compatible SIM cards with mobile carriers like China Mobile and China Unicom. They allow passengers to just tap phones on the relatively small number of Metro turnstiles bearing an NFC sign.

Some passengers have complained that the system doesn’t always work well, requiring repeated tapping to activate the gates.

The new system to be initiated by late June will reduce card refilling time to just a few clicks anywhere, anytime.

“People can refill only via Union Pay at first,” said Ma Xiaofeng, spokeswoman for the card company. “Third-party payment systems like Alipay will be integrated into the platform later.”

NFC is at the cutting edge of payment systems. It allows two devices to exchange data even at a distance of a few centimeters apart. Popular NFC-compatible phones include Samsung Note 3 and Xiaomi Mi3. The iPhone 6, though equipped with the right chips, supports only NFC payments via Apple Pay and cannot be used under the new service.

Netizens commenting online about the new service said they want to be able to refill their Metro cards through WeChat, the most popular instant messaging system in China. Currently they can pay for taxis through WeChat but there are no plans to extend that level of service to the Metro in Shanghai.

Upgrading Metro cards is part of grander plans to make travel by Metro more seamless. The system carries about 8 million riders a day.