UEFA has said VAR will be used to support match officials in four "match-changing" situations during games in the Champions League knockout stages.
European football's governing body has sanctioned the introduction of the review process from the round of 16 onwards.
The Champions League resumes on Tuesday, with Manchester United's home game against Paris Saint-Germain and Porto's trip to Roma the first fixtures in which VAR can be used.
"The VAR will be used in order to support the referee when making decisions concerning four match-changing situations -- goals, incidents in the penalty area, red cards and mistaken identity," a UEFA statement said.
"The VAR will inform the referee when there is evidence of a clear and obvious mistake in one of these match-changing situations. The referee can then use the review area next to the pitch to take a final decision.
"The VAR is also able to take into account any infringement that could have taken place in the immediate buildup to the incident (the attacking phase of play)."
Offside decisions and the area in which a foul was committed can also be looked at, with UEFA outlining that no on-field review by the referee would be required.
"Decisions like offside or whether a foul was committed inside or outside the penalty area will be recommended to the referee directly by the VAR and no on-field review necessarily takes place in such cases," the statement said.
"The on-field review process will be communicated within the stadium using either the stadium screens or the public announcement system."