Mayor Rahm Emanuel is expected to announce the donation at a Friday afternoon event.
The money will go to Woodson Regional Library, Whitney Young Branch and the new Altgeld Branch. The donations will be used to support "Experience Labs" that feature YOUmedia digital labs for teens, CyberNavigator digital skills tutoring for adults and Maker Lab programming.
Comcast will also donate 20 laptops to Lovett Elementary School students, the city said. It's all part of an effort to close the digital divide in the city.