Liverpool stormed into the Champions League semi-finals for the second consecutive season after weathering an initial storm from the Portugese side.
The reds ran out comfortable winners both on the night and on aggregate, thanks to goals from the front three and Virgil van Dijk.
Klopp started with Origi instead of Firmino, but replaced the Belgian at half time with Liverpool already 1-0 ahead.
Liverpool can now prepare to face Barcelona in the semi-final with the first leg in the Nou Camp where they will face former players Luis Suarez and Philippe Coutinho.
Klopp made three changes - bringing back Wijnaldum and Milner, and preferring Origi over Roberto Firmino.
Porto knew they were up against it and came flying out of the blocks looking to secure that first goal to give Liverpool some jitters. They didn't manage the goal but they certainly caused Liverpool's defence some anxiety.
Within 100 seconds Jesus Corona had powered into Liverpool's area and curled a shot narrowly over the crossbar.
More chances came their way but perhaps none as clear as that initial one.
The reds, despite their 2-0 lead, didn't look their usual calm selves but all that changed in the 25th minute with Liverpool's first attack of the game.
There was a slight delay before Mo Salah peeled away celebrating. He had seen the video at the side of the pitch, and a few seconds later the referee gave the goal.
It was a killer blow for Porto - taking the winds out of their sails.
Roberto Firmino came on at half time to replace Divock Origi who did not enjoy the best of the first half and Liverpool went on to complete their mission.
Alexander-Arnold fed the ball through to Salah who fired in for his 23rd goal of the season.
Porto grabbed one back through Militao but it was all too little too late, and Liverpool hadn't finished.
Another substitute, Henderson, then sent in a cross for Firmino to head in before Van Dijk headed in after Sadio Mane headed on a James Milner corner.
Liverpool's work was done and done admirably.
Barcelona up next in what will be a serious step up in class as the prospect of another Champions League final rears its head.
Allez, Allez, Allez!