High school student Nathan Myers, 17, is seen at Quince Orchard High School in Gaithersburg. Myers is one of many students experiencing difficulties using an online college application form. (Evy Mages/For The Washington Post)

A cascade of glitches in a major online college application program has frustrated prospective students across the country and prompted several universities to push back their fall deadlines, exposing vulnerabilities in the nation’s college admissions system.

More than 515 colleges and universities, including the entire Ivy League and public flagships such as the University of Virginia, use the Common Application to help choose their incoming classes. The program, which handles millions of applications annually, was retooled this year in an attempt to make an inherently stressful teenage ritual a little easier. But the fourth online version of the Common App, which went live Aug. 1, has compounded the angst of many college-bound students.

Software troubles and other technical difficulties have left students staring at frozen screens or led them to pay multiple fees for a single application. Others reported being shut out of their accounts entirely.

Arjun Iyer, 17, of Herndon, a senior at Thomas Jefferson High School for Science and Technology in Fairfax County, said he tried to log in about 10 times on the eve of a deadline to apply to the University of North Carolina at Chapel Hill. At one point, the computer told him that his user name and password didn’t exist.

“Of course I was freaking out a little bit,” he said.

Some counselors said they were having trouble uploading recommendations and other required documents.

“A lot of us are pulling our hair out,” said Marisha Wright, a counselor at Eleanor Roosevelt High School in Prince George’s County. Like many of her peers and students nationwide, Wright struggled last week to overcome technical difficulties in filing materials for UNC and Georgia Tech until those two schools extended early application deadlines.

Leaders of the Common App, a nonprofit organization based in Arlington, acknowledged shortcomings in serving students nationwide, but there was no estimate of the number of students who experienced problems.

“For many users, the new Common Application has not been a reliable service,” they said in a statement Friday, pledging improvement.

A key deadline looms Nov. 1 for students who are seeking early admission to many prestigious schools. Reports of Common App struggles led the University of Chicago and Columbia, Duke and Northwestern universities to extend their deadlines one week, to Nov. 8. Princeton University, a Common App user since 2004, announced it would give students a second option: an online form called the Universal College Application.

The lesser-known UCA is seeking to capi­tal­ize on the Common App’s stumbles.

“The conversation now is, we do need multiple vendors,” said Joshua Reiter, president of ApplicationsOnline, based in Baltimore, which runs the UCA. “There are alternatives.”

Common App officials say they are racing to troubleshoot their software and are confident it will meet challenges coming with application deadlines in November and January. Scott Anderson, senior director for policy for the Common App, said more than 229,000 applications had been filed successfully as of Friday, up 19 percent from the previous year’s total at that date.

“Many, many students have been able to submit just fine,” Anderson said. “But for those who can’t, it’s maddening. It’s frustrating. . . . We are apologetic and regretful that they find themselves in this position.”

Hobsons, a Cincinnati-based contractor that provides technical support for the Common App, said in a statement: “We want all users to have a positive experience and we regret that this has not recently been the case.”

Version 4 of the Common App replaced a six-year-old system that officials say had been showing its age. The new form is less cluttered and more interactive than its predecessor, helping students more easily track their applications. Bold, green check marks pop up as steps are completed. Minus the glitches, students like it.

“It’s an excellent way to manage college applications,” Iyer said. He eventually filed his application to UNC and plans to file others soon. But he panned the Common App’s customer service. There is no phone number to call for help. Queries must be submitted online. Troubleshooting guidance, Iyer said, was slow to appear on the Common App’s help and Facebook pages.

In some ways, the Common App is a victim of its own success. It started in 1975 as an association of 15 private colleges, including Carleton, Goucher and Vassar, that wanted to simplify the application process so students would not have to duplicate effort.

There were 191 member schools when the online Common App debuted in 1998. The number has rocketed in the past decade as schools across the country have moved toward digital systems and phased out paper. Public institutions were invited in 2001. To join, schools must commit to “holistic” admissions, which means they consider more than just grades and test scores.

In the last school year, 723,576 students sought college admission through the Common App. They sent in more than 3 million applications, more than four per student.

Nathan Myers of Gaithersburg found the experience of applying to UNC-Chapel Hill surreal.

Myers, 17, a senior at Quince Orchard High School in Montgomery County, logged into his Common App account Oct. 10, five days ahead of UNC’s early-action deadline. He had finished his application and was ready to submit it, but he couldn’t get the document to load.

For three more days, he tried various computers and various Internet browsers. Each time, the screen showed a “little dial spinning, for about 60 minutes,” Myers said.

His parents pitched in.

“We were taking shifts on watching the spinning wheel,” said his father, Lew Myers. “I would go in there and check it out. My wife would go in there and check it out. It was quite the journey.”

The breakthrough came Oct. 14: The document loaded. Nathan Myers paid his $80 fee and filed. Then, for a day, the payment didn’t register. “It kept asking me to pay again,” he said.

Common App officials say they are working to ensure that any students who overpay get refunds.

Until the glitches surfaced, one of the biggest debates over the revised Common App centered on its five essay prompts. Example: “Recount an incident or time when you experienced failure. How did it affect you, and what lessons did you learn?” This year, there is no longer an option for students to write about a “topic of your choice.”

Many schools in Maryland, Virginia and the District use the Common App. Notable exceptions are two large public universities in the Washington suburbs: the University of Maryland at College Park and George Mason University. Georgetown University is also a holdout.

Georgetown accepts applications through its own Web site or on paper. The Common App stopped using paper this year.

“Obviously, for everyone’s sake, we hope the Common App works since so many students are involved, virtually all for that matter,” said Charles Deacon, Georgetown dean of admissions. “It is unfortunate that they eliminated the paper option because it does leave them and the entire process totally vulnerable to some major collapse.”

About 35 percent of the 517 member colleges and universities use the Common App exclusively. For those schools, it could prove hard to come up with a Plan B if the system were to fail. Georgia Tech’s director of admission, Rick Clark, said the school expected start-up bumps when it joined this year. “Obviously, those have been more magnified than we would have hoped or expected,” Clark said.

But Clark said the simplicity of the Common App has driven up application numbers, drawing prospective students from markets far removed from the school’s regional base.

Nicole Welch, 17, a senior at Walt Whitman High School in Bethesda, said she thought the Common App was great until she tried to apply to Georgia Tech and UNC on Oct. 14 and was stymied over and over again. Finally, she set her alarm for 3:30 a.m. the next day. She woke up, signed on and — at last — filed. But Welch would hardly describe herself as a satisfied customer. “It does not feel like they succeeded in making it more user-friendly at all,” she said.