Briton Froome rolled over the line in third at 20sec, just ahead of Porte, to take the race leader's yellow jersey off his compatriot and team-mate Geraint Thomas, who drops to second, although at the same 12sec gap that he previously enjoyed.
But a trademark surge from Kittel saw the 29-year-old German secure a twelfth career win on the Tour and draw level with Erik Zabel as his country's leading stage victor.
"I'd say that stage is going to be very decisive".
Eurosport is the home of the Tour de France. Arnaud Demare of FDJ holds it for now, but Kittel is closing in after his second win of the Tour.
"Probably, you know, could have had the same result with half the distance but it's a nice one to get done", Porte said. Reminds me of last year's stage in Limoges, but not even that one was so tight.
"The final 300 metres were awful, but then when I looked back with 200 metres to go, I knew I'd got it".
"It's just insane. Being back here now in the Tour. celebrating now already three stage wins is incredible".
"It's an incredible feeling to be back in yellow, but having said that I know race far, far from over, it's only just begun for me", said Froome.
"Of course (it will be easier) but Sagan was already behind me when I took the jersey - it's going to be a big fight", he said. "I'm not a pure sprinter, so to be able to be up there on these flat stages gives me a lot of confidence for the remaining part of the Tour", Boasson Hagen explained.
Matthews, who won a stage in last year's Tour when he rode for the Australian Orica-Scott team, has also been outspoken.
Quemeneur picked up the solitary point over the two fourth-category climbs on the menu while Backaert pocketed some prize money for his wildcard Belgian team in the intermediate sprint.
Kittel led the points competition after stage seven on 197 points, followed by Demare on 182 then Matthews on 123.
"I could start my sprint from a great position - a little bit from behind so I could see where my opponents would go - and yeah, I feel good at the moment".
"Coming from a long way back to ending up where I ended up was a massive confidence booster", he said.