When the investigative journalist Julia Angwin worked for ProPublica, the nonprofit news organization became known as “big tech’s scariest watchdog.”

By partnering with programmers and data scientists, Ms. Angwin pioneered the work of studying big tech’s algorithms — the secret codes that have an enormous impact on everyday American life. Her findings shed light on how companies like Facebook were creating tools that could be used to promote racial bias, fraudulent schemes and extremist content.

Now, with a $20 million gift from the Craigslist founder Craig Newmark, she and her partner at ProPublica, the data journalist Jeff Larson, are starting The Markup, a news site dedicated to investigating technology and its effect on society. Sue Gardner, former head of the Wikimedia Foundation, which hosts Wikipedia, will be The Markup’s executive director. Ms. Angwin and Mr. Larson said that they would hire two dozen journalists for its New York office and that stories would start going up on the website in early 2019. The group has also raised $2 million from the John S. and James L. Knight Foundation, and $1 million collectively from the Ford Foundation, the John D. and Catherine T. MacArthur Foundation, and the Ethics and Governance of Artificial Intelligence Initiative.

Ms. Angwin compares tech to canned food, an innovation that took some time to be seen with more scrutiny.