U.S. companies will need to know more about where they store e-mails, instant messages and other electronic documents generated by their employees in the event they are sued, thanks to changes in federal rules that took effect Friday, legal experts say.

The changes, approved by the Supreme Court’s administrative arm in April after a five-year review, require companies and other parties involved in federal litigation to produce “electronically stored information” as part of discovery, the process by which both sides share evidence before a trial.