The measure passed 8-3 exempts the micro-blogging service from paying payroll tax on new hires if it moves to the city’s neglected Mid-Market area.

”This is a tax policy designed to revitalize neighborhoods in San Francisco that have been blighted for decades,” said Board of Supervisors President David Chiu, who was also one of the measure’s sponsors.

The exemption applies beyond Twitter, to any business in the Mid-Market or Tenderloin neighborhoods, on or near Market Street between Fifth Street and Van Ness Avenue. But city officials called Twitter the big fish that could spur economic growth.

Twitter is already outgrowing its current San Francisco headquarters in the city’s South of Market neighborhood, and the company is poised to expand from a few hundred to a few-thousand workers.

While seeking a building with more office space, the company had said it had considered moving down the Peninsula to a city that has no payroll tax.

But last month, Twitter signed a letter of intent to sign a six-year lease and move into the San Francisco Mart building on the southwest corner of Market and Ninth streets, contingent upon supervisors approving the tax break.

Soon after, Zynga, maker of social games like Farmville, indicated it would leave its San Francisco headquarters unless the tax break was expanded to include it. Other online companies like review site Yelp and real estate site Trulia indicated the payroll tax was among the reasons they were adding jobs outside of the city.

San Francisco is the only city in the state that charges companies a payroll tax; 1.5 percent of total employee compensation each year if the firm has more than $250,000 in payroll. The tax also applies to money made on stock options, a prime consideration for Twitter and Zynga which are both rumored to be exploring initial public offerings.