Students in Math 21a: “Multivariable Calculus” were already stressed for their midterm Thursday. Then Canvas, Harvard’s platform for course websites, stopped working.

Suddenly, students busily preparing for the Math 21a exam could no longer access class worksheets, practice exams, or problem sets.

“It was really annoying,” Math 21a student Aileen D. Villalpando ’20 said.

Canvas remained nonfunctional much of the day Tuesday due to a service glitch at technology company Amazon. The disruption in Amazon’s web services, which began at noon and lasted for roughly five hours, temporarily downed large swathes of the Internet, including popular sites Netflix, Airbnb, and Slack, The Seattle Times reported.

The Canvas outage alarmed many Harvard students, prompting some teaching fellows to extend homework due dates and send out messages of reassurance.

Course staff for at least two classes—Computer Science 124: “Data Structures and Algorithms” and Statistics 123: “Applied Quantitative Finance”—emailed students noting the server lapse and pushing back deadlines for assignments slated to be turned in via Canvas. Janet Chen, a preceptor in the Mathematics department and the course head for Math 21a, re-posted practice exams and problem sets on a different website Tuesday afternoon so students could access the documents.

“That was definitely a good thing,” Villalpando said of Chen’s actions.

Still, Chen was only able to re-upload course materials around 3 p.m., meaning some Math 21a students lost several hours of studying.

“I wasn’t really planning on studying at that moment but I can definitely see if anyone had decided to spend today as a study day for Math 21a—I would have been really annoyed,” Villalpando said.

Abdul Saleh ’20, who is also taking Math 21a, agreed with Villalpando. He wrote in an email Tuesday evening that the Canvas malfunction likely “freaked out” many students in the class.

Harvard University Information Technology sent a message to Harvard affiliates informing them of the Amazon and Canvas outage around 5 p.m. Tuesday, and posted updates on the situation to its website throughout the day.

“Canvas and other applications hosted by [Amazon] are experiencing slow or interrupted performance,” the HUIT email reads. “We apologize for any inconvenience this may cause.”

Computer Science 124 teaching fellow Evan Yao ’17 said students in his class had mixed reactions to the Canvas outage. He said some began to panic when they realized they could not turn in their programming problem set, originally due—if students used one “late day”—at 5 p.m. Tuesday.

Course staff later extended the deadline to midnight.

“The students were stressed out by it because they were panicking because they couldn’t turn in their homework,” he said. “But we assured them there would be no problem, we understand, everything would be alright.”

“Other students were happy about it because, for once, Canvas helped them—Canvas gave them an extra seven hours,” Yao added.

Amazon resolved the situation, causing Canvas to come back online, around 5 p.m.

Reflecting on the day’s events, Villalpando said Amazon’s technological struggles made her reconsider her dependence on Canvas and other sites.

“It’s just that, with more reliance on online websites—even though it does make it easier for us to streamline our work and send documents online and not have to worry about printing out papers and turning them in in person—it makes these kinds of events very impactful on us,” she said.

—Staff writer Hannah Natanson can be reached at hannah.natanson@thecrimson.com. Follow her on Twitter @hannah_natanson.