A sharp sell-off in tech pushed the Nasdaq Composite and S&P 500 lower on Wednesday. Investors also braced for another round of trade negotiations between the U.S. and Canada.

The tech-heavy Nasdaq Composite dropped 1.2 percent — its worst day since Aug. 15 — to 7,995.17 as Facebook, Amazon, Netflix and Alphabet all dropped. Shares of Microsoft and Twitter also fell to drag the index lower. The declined 0.3 percent to 2,888.60 with tech pulling back 1.5 percent.

Tech shares fell as Twitter CEO Jack Dorsey and Facebook COO Sheryl Sandberg testified in front of Congress, addressing online election meddling and how to stop abuse on social platforms.

"When you have these corporate executives dragged to Congress, that makes the market more nervous," said Robert Pavlik, chief investment strategist at SlateStone Wealth. Pavlik noted the hearing raised concern over tighter regulations in the tech industry. "That's why you're seeing the market take more of a wait-and-see approach on these stocks."

The Justice Department said Attorney General Jeff Sessions will meet with state attorneys general later in September to discuss worries surrounding tech companies that "may be hurting competition and intentionally stifling the free exchange of ideas on their platforms."

Netflix shares dropped 6.2 percent, while Amazon and Microsoft both fell more than 2 percent. Shares of Facebook and Twitter dropped 2.3 percent and 6.1 percent, respectively.