MOUNTAIN VIEW, CA - SEPTEMBER 02: The new Google logo is displayed at the Google headquarters on September 2, 2015 in Mountain View, California. Google has made the most dramatic change to their logo since 1999 and have replaced their signature serif font with a new typeface called Product Sans. (Photo by Justin Sullivan/Getty Images)

The Justice Department is expected to file a lawsuit Tuesday alleging that Google has been abusing its online dominance in online search to stifle competition and harm consumers. The litigation marks the government’s most significant act to protect competition since its groundbreaking case against Microsoft more than 20 years ago. The suit could be an opening salvo ahead of other major government antitrust actions, given ongoing investigations of major tech companies including Apple, Amazon and Facebook at both the Justice Department and the Federal Trade Commission. Google has long denied the claims of unfair competition. Google argues that although its businesses are large, they are useful and beneficial to consumers.