Jansrud, skiing with his left hand strapped into the pole to protect two fingers he broke training in Kitzbuehel last month, laid down arguably the run of his life on the Olympia course, shortened to that of a super-G because of
overnight snow and later fog.
The 33-year-old clocked 1min 19.98sec for his maiden world title, Svindal roaring through the finish line just two-hundredths off the pace.
Austria's Vincent Kriechmayr claimed bronze, at 0.33sec, to go with his super-G silver.
"I've been sharing the podium with Aksel for quite a few times throughout our career and doing this on his last race at the world champs is an honour. This is a perfect day," said Jansrud, the 2014 Olympic super-G gold medallist.
"You keep on believing and fighting. After what happened in Kitzbühel with the hand, I had to fight harder.
It's nothing to explain, you fight every day as an alpine skier and sometimes you succeed and sometimes not."
Svindal admitted to huge pre-race nerves, saying: "This is more than I expected. I knew I was fast enough to get a medal... but to make it happen on the day is another matter.
"The last couple of days building up to the race, I've been nervous," he said. "But I wanted to give it all I had on my last race. It was a great show."
Hitting speeds around 130km/h, racers had to negotiate a testing course in limited visibility, the race having twice been put back in the hope the fog would clear.
Organisers it safe to go ahead and what a white-knuckle race it turned out to be. The rolling terrain propelled skiers 40 metres into the air at times and the top section included a bumpy traverse that saw many go wide on a tight right-turn re-entry.
When Jansrud came through to the finish, wearing bib number six, it was as if he already knew he had done enough for victory.
He punched the air, quickly unhitched his right ski, grabbing it and shaking it towards a stadium seemingly full of Norwegian fans.
"Getting the roar from the all Norwegians and Swedes on the stand was one of the most amazing feelings in my career, just almost getting blown over from the sounds! It's a very emotional day and I'm going to enjoy it," said Jansrud.
Then it was the turn of Svindal. The big screen first flashed up Jansrud sitting on the leader's chair before cutting to Svindal in the start gate.
The already-pumped up crowd went mad, their roars drowning out the cowbells of the Swiss and Austrian fan clubs.
Svindal gave his all, but had to be content with finishing second to his close friend in a reverse of the Pyeongchang Olympics downhill result. "It's a great race, a close race," beamed Svindal.
"The roles were switched at last year's Olympics, yep, perfect today."
His silver medal brings an end to a career that ironically saw him win his first gold medals (downhill, giant slalom) in Are, back in the 2007 world championships. He won another downhill gold in Schladming in 2013.
His silver meant Svindal joined compatriot Kjetil Andre Aamodt (seven) and Luxembourg's Marc Girardelli (six) as the only skiers to collect a medal at six world championships. US women's star Lindsey Vonn can also achieve that feat in her farewell downhill race on Sunday.