The Internet has largely shoved aside the old Yellow Pages commercial phone directories.
A Swedish start-up called Truecaller aims to do the same for the world's White Pages personal listings and their online progeny.
While a quick Web search can unearth the phone number, address and much more about most businesses, it's harder to find accurate information about people - especially as millennials abandon landline phones for mobiles, which typically aren't included in directories.
"If you go to the White Pages and search for Alan, you'll never find the right Alan," said Truecaller co-founder Alan Mamedi. "That's where we're unique."
Mamedi teamed up with former college buddy Nami Zarringhalam in 2009 to create the app, which catalogues the contact lists of everyone who registers, so if a sufficient number of its 100 million-plus users know the John Smith in Brooklyn you're seeking, you can find him.
And the app predicts which John Smith you want - or, more likely Rajiv or Aditya, since it's gained the most traction in India - making suggestions based on the people you know. Just as important, Truecaller will show on your phone's screen the identity of callers who are among the 1.6 billion numbers in its database, and it allows you to block calls you don't want.
The company last year raised $80 million in venture funding from the likes of Kleiner Perkins Caufield & Byers, Sequoia Capital, and Atomico, the tech startup fund of Skype founder Niklas Zennstrom. Among Truecaller's pool of advisers are Google board member John Doerr and William "Bing" Gordon, co- founder of Electronic Arts.
Truecaller is "redefining the mobile phone book," said Mattias Ljungman, managing partner at Atomico.
The team is on track to transform the way we use our phones.
The growth and venture interest make Truecaller look like it could be the next WhatsApp, the messaging service that last year was acquired by Facebook for $22 billion. Though Truecaller remains shy of the 450 million users WhatsApp had when the deal was announced, Mamedi expects to top 300 million accounts by year-end. He declined to provide a valuation for the company.
Truecaller is "very clever - a classic crowdsourcing exchange where you give data in return for a useful service," said Martin Garner, an analyst at CCS Insight in London. While Truecaller's "potential for further growth is very high," though, Garner said WhatsApp's valuation got a big boost because it posed a potential competitive threat to Facebook - something that's less clear with the Swedish company.
So far, most of Truecaller's growth has come in India, home to more than 55 million of its users, followed by Egypt. That's because those countries have no comprehensive public telephone directory and many people use pre-paid phones, which are tough to track.
"It really helped me while I was looking for a job, because I knew which company they were calling from," said Ragesh Nair, 28, who works in social media marketing in Bengaluru, or Bangalore.
Zarringhalam and Mamedi, both 30, met as engineering students in Stockholm. After starting a furniture-shopping portal that failed to catch on, they came up with an early version of what would become Truecaller and spent much of the next two years crafting the app at a table in Zarringhalam's kitchen. The same Ikea table stands today in the conference room at the company's Stockholm headquarters.
Between 2010 and 2013 they raised 2.5 million euros ($2.7 million) from a handful of investors, but they struggled to get more substantial backing. Then Facebook CEO Mark Zuckerberg started saying mobile users - most of them from fast-growing new economies like India - would make up the bulk of the social network's next billion customers.
"Everyone wants to be where the successful entrepreneur wants to be, and we were already there," Mamedi said.
One concern about crowd-sourced information like Truecaller's is privacy, said Jessica Ekholm, a research director at Gartner. She predicts that the company's growth could slow as more people pause at the idea of opening up their calendars and contact lists to outsiders.
"We're just at the tip of the iceberg of consumers' awareness of app security," Ekholm said in an email.
Zarringhalam said the app has ample protections, with settings that let users limit who can see their data - friends of friends or all Truecaller users - and allow their details to be shown only on request. Non-users get a message when someone wants to connect, and there's a button they can click to be delisted entirely.
"We're giving everybody the ability to control their own information," Zarringhalam said. "You don't get content you shouldn't have access to."
Truecaller faces competition from a multitude of companies that offer ad- or subscription-based directory services using data from phone operators and public sources. Even with millions of numbers, though, Mamedi insists they aren't as comprehensive as his crowd-sourced directory, which can provide multiple listings - mobile, residential, office, and more - in places where there may be no decent phone book.
Mamedi says making money with all that information is of secondary importance for now. One possibility is more business listings - Truecaller last year signed a deal with review site Yelp Inc. - which could let the company make money from business listings and still provide free data to consumers.
"Our only focus is growth, but we're excited about monetization because that's something we want to focus on later," Mamedi said. "We have a lot of ideas."