Mint.com offers free online tools to manage your money, and it’s been a huge success. Intuit decided to pull the trigger and buy it.

Intuit is buying Mint.com for $170 million in cash, in a deal that gives it control of a startup that had disrupted its dominance in personal money management software with a free online alternative. Intuit, which sells Quicken, and Mint had been in a tight race in the online personal finance market, with both companies claiming more than one million active users of their online products. Last fall, Intuit dropped the $2.99 a month subscription fee that it was charging for Quicken Online, partly in order to better compete with Mint. Intuit says it will now offer both services separately, although it says Mint will be the “primary online personal finance management service” it will offer to consumers.

Both sites make money by referring users to financial services like credit cards and credit counseling services. I guess the free service model still works!