Two decades ago, when I was a student in a part-time master’s degree program at Johns Hopkins University, I would hurry from my office twice a week to make class, hoping like many of my classmates for a few minutes to grab coffee and a bite to eat before settling in for the 2 1/2-hour seminars.

Next week, when I address the graduating class of the same school, most of them will probably be meeting face to face for the first time at commencement: Seventy percent of this year’s graduates earned their master’s degrees online.

Once the backwater of higher education, online learning is now mainstream. At a time when overall enrollment in higher education is declining, the number of online students continues to climb. More than 6.3 million students took at least one online class in 2016, according to an annual analysis of federal data by the Babson Survey Research Group. That represents 32 percent of all students in higher education, up from 26 percent in 2012.

The expansion of online education has coincided with concerns about the price of brick-and-mortar education. And it has arrived as much-improved technology gives time-pressed, place-bound adults the flexibility to earn a degree. That flexibility has often translated to concerns from campus-based academics about the quality of online classes. But those worries seem to be subsiding. In part, that’s because the big for-profit providers, which were responsible for the early growth of online education, are losing market share to traditional brand-name colleges, particularly public universities.

Employers are also playing a significant role in the enhancement of online education. The United States has 6 million vacant jobs — 1 million in health care alone — according to the Labor Department. While employers might have been skeptical of online degrees a decade ago, today they are most worried about hiring workers with high-quality skills.

“We see online programs as the wave of the future for filling our talent needs,” said Nancy Vish, president and chief nursing officer of Baylor Jack and Jane Hamilton Heart and Vascular Hospital in Dallas. Even so, Vish added, “we tell our nurses to be selective in finding the right school.”

As hospitals increasingly require nurses to have a four-year degree, one of the most popular online degrees is the “R.N. to B.S.N.,” for people who are already registered nurses to earn a bachelor of nursing degree. There are 4.2 million nurses in the United States, and about one-third lack a bachelor’s degree.

One of the largest online nursing programs is at the University of Texas at Arlington, with nearly 11,000 students — part of a broader online strategy the university has pursued over the past few decades. The school started to put courses online in the 1990s to offset a sharp drop in enrollment. By 2008, it had 5,100 students enrolled in at least one online course. That’s when it partnered with Academic Partnerships, one of several companies that help nonprofit universities build online programs and recruit students.

“Online education is a way for us to reach what is the new traditional student in higher ed, and that’s not an 18-year-old but an adult student looking for a college degree to change her life,” said Vistasp Karbhari, UT-Arlington’s president. “So we’re focused on face-to-face, online and a mix of the two to provide education in the form, location and time that is convenient to the students who need it to get ahead in this economy.”

Given that the largest online programs UT-Arlington offers are in nursing and education, Karbhari told me, the university can’t afford to turn out low-quality online degrees. Hospitals and schools usually recruit at institutions based on their previous hiring experiences. “You’re always judged on your last class of graduates,” he said.

I first became familiar with the University of Texas at Arlington in 2013, when I contributed to a project at New America, a nonpartisan public policy think tank. It studied public universities that had been able to expand enrollment and achieve higher graduation rates in a cost-effective manner. The Arlington campus was one of six selected after an analysis of federal higher-education data.

In the five years since that report was published, UT-Arlington’s online enrollment has continued to climb, making it one of the fastest-growing universities in the country. Today, 57 percent of UT-Arlington students take at least one class online, and of those students, 45 percent are enrolled exclusively online.

One of the fully online students is Tara Bordeaux, who is scheduled to graduate in August with a master’s degree in curriculum and instruction. Bordeaux started online courses with UT-Arlington in 2012, while working in the film industry in Los Angeles. She wanted to become certified as a teacher. Now, she teaches audio and video production, filmmaking, and photography at Lanier High School in Austin, where she was recently named teacher of the year in the state.

Bordeaux was an early pioneer in online education 20 years ago, when she took a few online courses by checking out videotapes from a community college. “I felt like those were watered-down courses,” she said. But with the widespread use of broadband, online courses have improved enough, Bordeaux told me, that they are often as challenging as, or in some cases more difficult than, face-to-face classes.

Advances in online technology allow students in many programs to take synchronous courses, in which students watch remotely at a set time, and asynchronous classes, which allow students to watch at their own pace. Synchronous online courses, Bordeaux said, require students to “step up their game,” because unlike in a face-to-face class, you can’t hide in the back of the lecture hall and rarely, if ever, get called on. “You’re out there in an online class for everyone to see,” she said. “If you don’t participate during class or on discussion boards, it’s easily noticed.”

Another reason online education became a popular strategy at public universities is that it’s seen as a way to expand enrollment amid declining state appropriations. That’s what Jonathan Becker, associate professor of educational leadership at Virginia Commonwealth University, called in a recent blog post “chasing a pot of gold at the end of the distance education rainbow.”

If they’re only about making money, the online efforts of universities will fail. But for many colleges, online programs are part of a broader movement to ensure that students graduate with a credential. In the California State University System, more than 100,000 students choose to take at least one online course because face-to-face courses are often full and unavailable. Without the online option, it would take students longer to graduate, or many might drop out short of a degree.

“Distance education can and should be a legitimate part of an institution of higher education’s overall mission,” Becker said. “Higher education can meet workforce demand via distance education. But they must do so with attention to program quality and outcomes.”