The rule makers also said at their meeting in the World Cup host nation of Qatar that the number of substitutes on a team sheet can rise from 12 to 15.
Using five substitutes instead of three started as a temporary measure in 2020 amid fixture congestion when football restarted during the coronavirus.
It was extended several times before now being permanent amid "strong support from the entire football community". Coaches have three slots during a match, plus half-time, to make substitutions.
It has been used in most major leagues since 2020 although England's Premier League went back to three substitutions last season. However, its clubs have agreed on five for 2022-23.
The assembly also got an update on semi-automated offside technology to assist referees and their assistants, and FIFA president Gianni Infantino and its referee boss Pierluigi Collina spoke positively about the camera-based technology which may be used at the World Cup.
"It looks very good and promising. Our experts will look at it before we make a decision whether to use it at the World Cup or not," Infantino said of the technology trialled at the Arab Cup and Club World Cup.
Collina said they were not a hurry because "we want to be sure that it works perfectly."
In other decisions, the IFAB extended tests of additional permanent concussion substitutions until 2023, preferring this over temporary substitutions.
Kick-ins instead of throw-ins, referees explaining key decisions during games, and fairer playing time were also discussed and according tests would require permission from IFAB and FIFA.
The assembly also meanwhile also approved tests with body-cams for referees in grassroots games to better protect officials.
"It can not happen on any pitch in the world that players are parents attack the referee," Infantino said.
