Major League Baseball is one of the most tech-savvy professional sports leagues around and that became more evident today as 13 teams will now be accepting mobile tickets using Apple’s Passbook app.

Passbook is an iOS app that lets you electronically store things like tickets, coupons and gift cards. This season, which kicks off in April, there will be 13 stadiums allowing fans to purchase paperless tickets and redeem through Passbook. That’s up from just four stadiums last season.

Unfortunately for Seattle Mariners fans, Safeco Field is not one of the 13 stadiums. Mariners marketing director Kevin Martinez told us that nothing is in place as of now.

MLB also released its update last week for the MLB.com At Bat app, which is the “No. 1 sports app of all-time.” It’s certainly the most robust mobile app I’ve seen in any league, and just one of the better apps I’ve used overall.

Last month, T-Mobile inked landmark deal with MLB to equip managers and pitchers with smartphones to communicate during games.

Previously on GeekWire: 3 ways your brand can learn from how sports team handle social media

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