When Marissa Mayer became CEO of Yahoo in 2012, one of her first tasks was to modernize the company's suite of mobile apps. The company brought hundreds of engineers into its then-tiny mobile division, and then lavished attention on its most-used apps. Weather, Flickr, Mail, and the flagship Yahoo app all received significant overhauls, and combined with the acquisition of Tumblr pushed Yahoo to be able to claim 1 billion mobile users every month. But one big product never got that upgrade, even as its category exploded in popularity around the world. This spring, Yahoo Messenger was pulled from app stores.

Today it's coming back. Yahoo Messenger, as the app is still called, is launching on Android, iOS, and the web. You can also find it inside Yahoo Mail, where it pops up as a Gmail-style talk widget. When you log in to the app using your Yahoo account, you'll find a clean, modern messaging app with a couple of nice twists. If someone sends you photos, they appear in a horizontally scrolling drawer, making them easier to browse in the middle of a conversation.

The photos stream in gradually until they arrive at full resolution, giving you the quality of the photos you receive on something like iMessage at much faster speeds. (They're backed up privately on Flickr, too.) You can also "like" messages by tapping a heart icon, as on apps like GroupMe, and un-send messages in case you ever accidentally tell your friends and family what you really think of them. The app also has native GIF search built in, powered by Tumblr.

"It's far from too late to start building the next big thing," says Austin Shoemaker, a director of product management at Yahoo, when I meet him in the company's San Francisco offices. Shoemaker says the Messenger team plans to release new features at a rapid clip, adding novelty to an app that is not particularly distinctive in its initial version. Before Yahoo acquired it last year, Shoemaker was a co-founder of CoolIris, whose products include a photo messaging app. The new Messenger builds off at least 10 acquisitions Yahoo has made in recent years, says Jeff Bonforte, the company's senior vice president of communication products.

Still, it's hard to shake the feeling that Yahoo has dithered when it has come to messaging, an area where it arguably had an advantage — or at least a large user base — compared to others. Facebook split its own Messenger off from the main app in 2014, and now it has 700 million monthly users. WhatsApp, which Facebook owns, has 900 million monthly users. In Asia, messaging apps like WeChat and Line have become hugely profitable through a mix of advertising, e-commerce, and integrations with other apps.

It isn't as if the trend has caught Yahoo unawares. In the summer it released LiveText, a hybrid messaging and video app, which has failed to gain much traction. Last year the company built a ho-hum messaging app called Instant, but abandoned it without releasing it after it failed to generate enthusiasm internally, according to people who saw it. Yahoo also acquired the startup MessageMe, which made an app whose feature set is much broader than the new Yahoo Messenger. MessageMe was shuttered, and its team did not contribute to the new Messenger, Bonforte told me, saying only that it was working on something else.

Yahoo says the technology behind Messenger will let it serve as a layer that connects everything inside of Yahoo. In the future, executives say, it could be used to stream apps to people's phones, or let them instantly message quotes from Yahoo News articles to friends. And in the meantime, they say, their fast photo sharing will prove appealing to the groups and families that remain a core constituency for Yahoo.

But it's an uphill battle. In the past, people have embraced new messengers because of some novelty in the experience (Snapchat's disappearing photos, say) or because their friends and family were already there (Facebook Messenger). There's very little novelty in the new Yahoo Messenger, and it's unclear how many new users will sign up for a Yahoo email address just to use it. (Give people the option of logging in with their Tumblr accounts and this would be a lot more interesting.) Bonforte said the company decided it couldn't wait any longer to rejoin the messaging wars. Within two years, he said, Yahoo Messenger "will be cutting edge." We'll see if it gets that long.