Twitter: @fluentinc

Principals: Ryan Schulke, CEO; Matthew Conlin, president

Headquarters: Manhattan

Three-year growth rate: 1,094%

2013 revenue: $52.7 million

Profitable? Yes

Local employees: 63

Total employees: 65

What it does: Offers a technology that matches e-mail newsletter subscribers and others to carefully targeted ads

How it grew: Ryan Schulke and Matthew Conlin aimed to go after lucrative business from online advertisers and publishers when they co-founded their startup, Fluent, in 2010. Fluent offers a technology that places, in real-time, what Mr. Conlin calls a “hyper-relevant” ad that it deems most appropriate to each reader who signs up for an online newsletter and others who respond to online offers, relying on data the subscribers have supplied.

One secret to its fast growth is a method of charging clients that users like. Instead of the standard cost-per-click (CPC) or cost-per-thousand impressions (CPM) model, advertisers pay on a cost-per-action (CPA) basis. That is, when consumers actively engage with an ad, as when they sign up for a loyalty club touted in an ad in an online newsletter. “They take the risk out of Internet advertising,” said a customer, who didn’t want his name used—lest competitors learn about Fluent.

Anne Field