In the previous NFL season, teams were only allowed to attempt an onside kick in the fourth quarter. However, a new rule has been voted on for the upcoming 2025 season which will allow teams to attempt an onside kick at any point in the game as long as they are trailing. See: https://www.nbcsports.com/nfl/profootballtalk/rumor-mill/news/owners-pass-rule-change-allowing-onside-kicks-at-any-point-when-trailing

Will any team make use of this new option? Note that only regular season games count. Pre-season and playoff games do not count. The kick must be attempted outside of the fourth quarter. An attempted onside kick counts even if the play is nullified by a penalty.