Arsenal celebrated in unison as Danny Welbeck's strike earned a 1-0 win that leaves Norwich's Premier League position ever more precarious.
The well-publicised protests in the 12th and 78th minute -- to signal 12 years since Arsenal's last Premier League title -- were a bit like the Gunners' season. Lots of expectation, poor execution.
And Welbeck gave Arsene Wenger reason for cheer and optimism of an 18th successive season in the Champions League with the decisive goal.
The Gunners' clash at Manchester City on May 8 will be crucial in determining their finishing position, while Norwich play at home to Manchester United the previous day desperate for points in their bid to avoid the drop.
A small minority took part in the protests and were shouted down by pro-Wenger chants. Arguments even broke out between rival factions.
There may have been greater agreement had the "Time for change" posters been directed at Giroud; the decision to send on Welbeck for Alex Iwobi, instead of the Frenchman, was jeered.
It was soon justified, though, as Giroud met Hector Bellerin's cross with a cushioned header that Welbeck drilled into the corner, three minutes after his introduction.
Norwich are still without a win at Arsenal since the opening day of the inaugural Premier League season in August 1992. They have won two of their last 15 league games, with 11 defeats.
Alex Neil's side dropped beneath Newcastle and Sunderland prior to kick-off, when a side showing five changes aimed to respond to the 3-0 loss to the Black Cats.
Norwich started well. Nathan Redmond forced Petr Cech to save after five minutes, after a Martin Olsson cross evaded everyone.
Cameron Jerome blasted over before arguments broke out between Arsenal supporters disputing the future of their club.
"There's only one Arsene Wenger" rang around the Emirates Stadium as the 12th-minute protest took place.
There was indecision off the field and on it, as Arsenal dithered around the Norwich penalty area, failing to fashion any real chances.
A deflected Mohamed Elneny effort resulted in a corner and Laurent Koscielny headed over.
Gary O'Neil had an opportunity on the break, exchanged passes with Redmond, but miscued his shot spectacularly over.
Redmond, Norwich's most lively player, made space for a shot which skipped wide.
Then came Welbeck's introduction, immediately injecting energy, and Arsenal's goal.
Redmond tried to create an equaliser, crossing for substitute Dieumerci Mbokani, but Gabriel, on for the injured Per Mertesacker, timed his intervention brilliantly.
Alexis Sanchez shot straight at John Ruddy from a Mesut Ozil pass on the counter attack.
The Germany playmaker then volleyed over before Elneny brought the ball down on his chest and fired with the outside of his boot. Ruddy saved.
The goalkeeper ventured forward in stoppage time, but Norwich's free kick barely reached him as they suffered another damaging defeat.