Pittsburgh (CNN Business) Noah Higgs hated learning Irish in school. He hated the way it was taught, overly formal and disconnected from ordinary people's lives. Most of all he hated the effect the lessons had on his fellow students' willingness to speak the language.

But the Dublin native never lost his love for Irish, nor his opinion that more people should be learning the language.

Today, almost 40% of the 7,000 languages spoken worldwide are endangered, according to the United Nations. More are going extinct every year

It was once widely feared that the internet revolution would speed up this decline. If developers and smartphone manufacturers aren't willing to invest in supporting minority languages, that would cut off people who speak them from an important way to communicate and trap those languages in the past.

Higgs, 23, though, is one of a small cohort of educators and activists reinventing how minority languages are taught and preserved online by using cutting-edge technology.

When he was 17, Higgs "had this kind of crazy teenage idea." He had begun using Duolingo, a mobile language-learning app, to study French, and wondered if the creators had considered adding support for Irish.

At the time in early 2013, there were five languages on Duolingo, the smallest of which, Italian, has an estimated 67.9 million speakers worldwide. By comparison, at its height in the 18th century, there were an estimated four million Irish speakers. Today the figure is closer to 1.2 million

"I didn't get a reply," Higgs said.

But his email wasn't ignored. Inside Duolingo's open-plan, Silicon Valley-style headquarters in Pittsburgh, Pennsylvania, change was afoot. Within five years, the language startup would build a library of over 30 languages , including some of the most imperiled on the planet.

Invention and reinvention

Duolingo is based on the idea that if learning is gamified and bite-sized (and free), people will stick with it when they might not otherwise. Users of its smartphone or web app are presented with short, five minute lessons in which they identify words, translate short sentences, or practice speaking and listening. Users earn points for passing lessons, and they can compete in daily and weekly leaderboards.

Duolingo's roots are in spam — or, rather, the fight against it. Co-founder Luis von Ahn made his fortune selling reCaptcha, the irritating but necessary software which makes you prove "I'm not a robot" when filling out certain forms online.

Von Ahn founded Duolingo while teaching at Carnegie Mellon University, alongside his graduate student Severin Hacker. Both were non-native English speakers working in the United States — von Ahn was born in Guatemala, Hacker in Switzerland — and they had seen how access to language learning had improved their earning potential. They wanted to create a free language app that would make money by providing translation services for other websites.

"(Von Ahn's) field of research has always been in human-computer interaction," said Duolingo spokesman Sam Dalsimer, who met with CNN Business at the company's Pittsburgh headquarters.

Duolingo founder Luis von Ahn speaks at an event in 2015.

Dalsimer described the app's original concept as one that would allow people to learn languages while simultaneously translating the internet. The translation part of the business model worked for a bit before the founders realized that artificial intelligence was quickly supplanting their human translators as the cheapest option.

Alphabet's GOOGL So they pivoted to focus exclusively on language learning. The founders also raised a lot of venture capital: They've brought in more than $100 million so far at a valuation of $700 million, with investments fromprivate equity firm, Union Square Ventures and Ashton Kutcher, among others.

Duolingo's lofty mantra fits right alongside the most ambitious in Silicon Valley: "Making language education free, fun and accessible for everyone in the world." But the company initially focused on the most profitable languages that had the biggest potential reach and userbase. It generated income by selling display ads against the courses and premium subscriptions, and by forging various partnerships.

Higgs' email arrived at the perfect time, when some in the company were questioning the focus on major languages like English and Spanish, and wondering whether they could expand the program to include smaller tongues.

Nor was Higgs the only person to email Duolingo asking the company to add a particular language, or to castigate the developers for choosing one language over another. The team was inundated with offers to volunteer to build courses for new languages, if they would only provide a way.

"People really wanted to contribute to get their language into the Duolingo system," community specialist Myra Awodey told CNN Business. Awodey works with language communities educators to develop new courses.

"That's kind of how the incubator came about."

In October 2013, Duolingo launched a program for anyone to begin building language courses . Even then, however, the incubator was originally conceived as a way to add new major languages — Russian was an early candidate — rather than minority tongues.

"But we had this heartfelt plea from I think a high schooler at the time," Awodey said. "(Our founder) was like, why not? This guy sounds cool. He's serious, let's just do it."

Irish became the first endangered or minority language added to the platform, though Higgs would not join the team for another year or so.

"They didn't choose me in the first round," he said, ruefully. But he was part of the team by the time Irish President Michael Higgins commended them at a public ceremony in 2016 for their contributions in preserving the Irish language, which he called "an act of both national and global citizenship."

By then, millions of people — more than the population of Ireland itself — had tried the Irish course, according to company data. Today, the language has more than 940,000 active weekly users, around the same as Hindi and Greek , languages with 615 million and 13 million speakers worldwide, respectively.

"Its been a massive, massive benefit to the language," said Oisín Ó Doinn, a learning technologist at Dublin City University and one of the original creators of the Duolingo Irish course. "It contributes to the ecology, the learning ecology around the language."

He said that many language learners in schools had begun using the app to supplement their studies, and that it has been a huge success in the United States thanks to pickup from the Irish diaspora.

An Irish-language sign reading "yield" in County Kerry, part of the Ghaeltacht, or Irish-speaking region of Ireland. The language has struggled in the past to present itself as a modern, living language that can be used country if not world-wide.

New approach to endangered languages

The success of the Irish course has cultivated a mini revolution inside Duolingo, which now employs 190 designers, developers, linguists, computer scientists and other staff in Pittsburgh.

"We had to focus in the beginning on the courses that had the most demand and largest audience served," said product manager Conor Walsh. "But the cool thing about technology is that the incremental cost decreases. Now that we have all these courses, and we've ironed out a lot of the technical complexity, now adding a new course, in many ways, doesn't cost us that much."

Access to minority language learning also has the ability to empower communities, he said.

Awodey, the Duolingo community specialist, agreed.

"I do feel like we have a responsibility as a company promoting these majority languages, and contributing to some of the trends that are further marginalizing minority languages," to do something about it, she said.

The legacy of colonialism worldwide has left numerous languages hanging on by a thread , as native tongues have been supplanted — often by force — with English, Spanish or other majority languages. Globalization has only accelerated the process, as those supertongues became even more economically and culturally powerful.

The digital revolution has been considered as having the potential to be the final nail in the coffin for many endangered languages. Digital language death happens when a tongue fails to "ascend" to the digital realm, meaning that it can't be used on smartphones or other parts of daily digital life, according to the Hungarian linguist András Kornai . That lack of relevancy can doom a language to history.

"It's really important that people see a language like Welsh as something they can interact with and use on modern devices," said Jonathan Perry, a language teacher who works on Duolingo's Welsh course. "It brings the language up to date with modern technology usage which is absolutely so essential that a language feels fresh and used."

Since Irish's rollout in 2013, Duolingo has added Welsh, Hawaiian and Navajo, along with the constructed global language Esperanto. Haitian Creole, Scottish Gaelic, Latin and Yiddish are currently in the incubation stage.

There's also a business justification. The more languages Duolingo adds, the more potential users are exposed to the app (and its advertisements). Minority and heritage language communities are also a user base where there is less competition from other services, as opposed to the multitude of apps which claim to help you learn French or Spanish.

"Irish was the test case because we were the first minority language on the platform and we're still one of the most popular courses," said Ó Doinn. (Irish is among the top 50% of courses as measured by active learners, and the most popular minority language.)

A man uses his smart phone as he walks along a street in New York on March 4, 2015. Some linguists have warned that the lack of support for minority languages on many platforms could hasten their demise.

Political red lines

Of course, there's a big difference between picking up a few words in Irish or Welsh to make you feel as if you're connecting with your ancestors, and actually learning a language — particularly an endangered one that needs all the speakers it can get.

This is a tension that Duolingo has struggled with when it comes to its two endangered language courses, Navajo and Hawaiian. Those tongues are listed as vulnerable and critically endangered, respectively, by UNESCO.

Both languages were added to Duolingo this year to coincide with the United Nations International Year of the Indigenous Language . But they raised questions that weren't necessarily an issue for courses such as French or Spanish, which aren't expected to be used by native speakers of those languages.

"Who's the audience for the Hawaiian course? Is it going to be tourists? Mostly? Because that would affect the content," said Awodey. "Or is it going to be primarily built by and for indigenous speakers and people reconnecting with the language?"

In Hawaii, the team partnered with Kamehameha Schools , a network of private schools dedicated to teaching students of native Hawaiian heritage with a particular focus on preserving the Hawaiian language.

Despite this, however, the Duolingo Hawaiian course can sometimes risk speaking down to native Hawaiians, few of whom need teaching, for example, what a "lei" is.

"Everyone was super excited about it, but it's totally tapered off because it's not for natives, it's too baby, it's too simple," said Kū Kahakalau, executive director of Hawaiian language and culture NGO Kū-A-Kanaka.

Linguistic politics are often fraught with regard to majority tongues, let alone for endangered languages that have a long history of colonialism and disrespect. Scrutiny of such courses is always going to be tighter, and invisible red lines easier to cross.

"When you're dealing with a heritage language, it does come with a bundle of stuff that we don't have when teaching English," said Duolingo learning scientist Hope Wilson. "There are lots of tricky issues to get into, very often there are divides within the communities where people don't agree on, you know, issues of spelling or that kind of thing."

For example, there was considerable skepticism when Duolingo announced that it had added an Arabic course, wading into a multi-country dispute over which version of the language to teach. Wilson wrote a long blog post explaining that the company chose to teach a less-formal version of the language often used in conversation.

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Visibility and viability

So does Duolingo actually work? The company pointed to an independent study carried out by researchers at the City University of New York of Spanish learners on the platform, which found a "statistically significant" improvement in their abilities.

This is supported by a wealth of anecdotal evidence from learners and course creators, and the sheer size of Duolingo's userbase. Many courses boast millions of active learners.

The app has faced criticism , however, that it overstates its effectiveness in some promotional material. Ads for Duolingo — including within the app itself — sometimes make outlandish claims, such as that "15 minutes a day can teach you a language." There is no silver bullet for language learning, and research supports the idea that immersion and active use are essential. Duolingo employees and course creators themselves emphasize the need for other forms of practice and learning outside of the app.

The question of effectiveness is particularly fraught when it comes to endangered or minority languages. But even if Duolingo isn't minting millions of new Hawaiian speakers, there are other ways in which the presence of a language on the app can help.

Visibility and prestige are vitally important to preserving and promoting endangered languages. Minority and endangered languages are generally at risk because they are marginalized within their own countries or communities. Anything that can improve their standing can go a long way to helping preserve them.

"Even if people aren't becoming entirely fluent with the app, it's hugely beneficial in terms of raising visibility and that's incredibly important," said Ó Doinn, the Irish course creator. "Status and support are the most important things for facilitating a language's usage."

Ó Doinn, Perry, Higgs and Kahakalau all pointed to the ability to have their phone's interface in their native language as a key factor in this regard.

"My phone is in Irish because I have an Android and I'm able to make that decision," Ó Doinn said. "My Gmail is in Irish. These things are done for free by the community for the community. If we open up those resources that people can modify themselves, that's really important for preserving minority languages online."