Two months ago, Boston-based app analytics company Crashlytics turned down an acquisition offer. Today, it’s turned the tables and acquired a company of its own.

Crashlytics has acquired FireTower app, a company that makes bug-detecting instruments for JavaScript. Crashlytics swiped FireTower from the hands of a competing acquirer at the last minute, founder Wayne Chang says. Many of Crashlytics’ 100 million app users have asked for analytics with more insights within the mobile Web. The company set out to build a solution and realized it would take six to nine months to even create the foundation.

Then he encountered FireTower and went after it from halfway across the world (he was visiting family in Taiwan). Crashlytics won. Now, if there is a crash on a company’s mobile website, Crashlytics has visibility into the cause of it. The company’s current offerings only serve apps.

Firetower was the project of Aaron White and friends, who now focus their time on the awesome textbook replacement company Boundless. Unlike Boundless, which recently raised a pile of money, Firetower was bootstrapped.

Crashlytics is also venture-backed. Founded last year, the company has raised $6 million from Flybridge Capital Partners, Baseline Ventures, CommonAngels and a number of angel investors. Thanks to that cash, its product is currently free. That’s how the company has amassed implementation on 100 million apps, Chang says. The company is working with users on a way to charge for its services.

Future acquisitions are on the table. “We hope to continue to build solutions and products for developers where they get enjoyment in using the tools rather than frustration,” says Chang.

Chang won’t say which company made an offer for Crashlytics. I asked about Providence-based Tracelytics, suggesting the company, which focuses on bug reporting strictly on the Web, might be a complementary fit. Chang didn’t disagree. He even jokingly suggested a name: Just “Lytics.”