Whether you’ve set up a Twitter account or never emitted a single tweet, you might have a few bits of software code sitting on your smartphone that were written at the company’s Cambridge office.

How’s that?

When Twitter acquired three local startups in 2013, shelling out more than $100 million in company stock, the San Francisco company suddenly had a presence here. But Twitter’s local employees don’t work on high-profile stuff like the Periscope live video app or that adorable heart-shaped “like’’ button. Instead, much of their effort is on advertising and tools that are used by people who create mobile apps — both of which could prove helpful to a company that has seen its stock price drop more than 60 percent over the last year.

Twitter’s first local acquisition, Bluefin Labs, happened three years ago this month. Bluefin was founded by a group of MIT Media Lab researchers, and the startup eventually developed software that could analyze vast numbers of tweets to understand which ones were about television shows and ads that people were watching live.

Twitter saw Bluefin’s technology as an interesting way to enable it to sell ads on its service to companies that wanted to reach viewers who were tweeting on their phones or laptops as they sat watching “Game of Thrones’’ or the Super Bowl — without necessarily paying millions of dollars for a broadcast ad. Instead, the viewers would see a sponsored message in the stream of tweets.

That offering is now known as TVxTwitter. Some of the people working on it are still in Cambridge, although a key Bluefin engineering exec, Jeremy Rishel, relocated to San Francisco. Twitter also laid off a dozen or so Bluefin employees immediately after the purchase, two former employees said.

Spindle was the smallest company Twitter bought in 2013; it had just nine employees. The Boston startup had created an iPhone app that let you see what was happening in the world of social media around you. If you were in Copley Square, for instance, you might see messages about restaurant specials, readings at the Boston Public Library, and concerts at nearby churches. But all of Spindle’s employees who wanted to keep their jobs got shipped to San Francisco, including two of the three founders, and the app itself was discontinued.

That’s what’s known in the tech sector as an “acqui-hire’’; Twitter paid a small amount to bring in engineers who understood social media and how it connected to the real world around us.

The core of the Cambridge outpost was built around the third acquisition, Crashlytics, a startup born when the two founders met at a 2011 dinner at The Beehive in the South End. True to its name, Crashlytics initially offered a service to mobile app developers to help them analyze why their apps were crashing after people had installed them on their smartphones. That let them identify bugs and quickly fix them, with a minimum of user aggravation.

That single product has evolved into a group of products for people who build mobile apps that Twitter now calls Fabric. It ­includes a tool for tracking how many people are using an app, how long, and even their demographics and interests. Another tool, Beta, lets app creators ­distribute early “beta’’ versions of their app to users, before the app has been released to the Apple iTunes or Google Play app stores.

The Fabric tools are now used by 225,000 app developers, according to Twitter, and as a result, some chunk of Fabric code now runs on about 1 billion Apple and Android smartphones, the company says. While the Fabric tools are free, they help Twitter in two ways.

First, they make it easy for app users to view or post tweets from within an app, like bragging to your Twitter followers about a trip you just booked or a high score in a game. The second thing the Fabric tools do for Twitter is they help app creators integrate advertising into their apps, which generates income for them — and Twitter gets a cut of the action.

The strategy of creating a suite of tools used by mobile developers is a way for Twitter to make sure that its content and advertising get seen by a large audience — ­including people who might not regularly use Twitter’s own app or website. “Mobile is where eyeballs are going,’’ said Brian Swift, a senior product manager at Twitter’s Cambridge office. “We’re looking at the biggest problems mobile developers have and seeing how we can help.’’

On Tuesday, Twitter threw a party for local app developers, complete with chocolate fountain and free T-shirts, to persuade them that it is in their corner for the long-term. (Facebook announced last month that it would discontinue its set of free developer tools, called Parse.) More than 100 showed up to learn about the Fabric tools.

Twitter continues to hire for the Cambridge office — 11 positions are open, and the gig includes free breakfast, lunch, and pinball. Last summer, Twitter acquired bought a local “machine learning’’ startup Whetlab, which added another five employees.

Still, Twitter’s operation hasn’t grown significantly in Cambridge. It employs fewer than 100 there, and a full floor of its building has yet to be occupied.

Rich Paret, general manager of the Cambridge office, said, “It’s definitely not a ‘satellite’ office situation. The teams here are working on some of the highest-priority work at Twitter.’’

We’ll see if that can help the company — and the Cambridge ­office — grow.

Scott Kirsner can be reached at kirsner@pobox.com. Follow him on Twitter @ScottKirsner and on betaboston.com.