What happened
Duolingo's (DUOL 2.09%) website and its foreign language-learning app both crashed this morning -- but not Duolingo stock. Instead of crashing, Duolingo stock soared and is up 10% as of 3:05 p.m. ET this afternoon.
Now why was that?

Image source: Getty Images.
So what
According to data from Downdetector.com, Duolingo first started having problems around 10:30 a.m. ET this morning. Well into the afternoon, these problems remain unresolved.
👋 We're aware of the issues you're experiencing with the Duolingo app and website, and we're working on a fix. We'll be back soon!
— Duolingo (@duolingo) December 7, 2021
In the meantime, know that your streak will be safe! https://t.co/GRbBZ4EiqJ
Ordinarily, you'd expect something like this to be bad news for a stock whose one and only product -- language software -- has been inaccessible to its millions of customers for essentially the entire workday. But investors are taking an entirely different cue from this event.
If you click over to Twitter, you see, the reactions from Duolingo's user base are not critical at all. Rather, they're adoring...
I only need a few lessons the past few weeks, then today I suddenly felt the urge to learn 😂😂😂
— Corey (@_equitial_) December 7, 2021
I'll wait for you my beloved
and perhaps a bit panicked...
Bruh I have a spanish mock exam TOMORROW. Now was not the time to shut down 😩
— Kebabi (@Kebabi19) December 7, 2021
and eager to see Duolingo come back online soon.
I am appeased by the stylish maintenance notification. Get well soon. pic.twitter.com/07YWmU2eZm
— Πρωταγορας محامى ذكى (@JaspersPhilipp) December 7, 2021
Now what
Why are Duolingo's customers so forgiving? Perhaps it's because the light-hearted tone of Duolingo's images, lamenting the site's off-lining, tends to blunt criticism. Or perhaps it's because the company doesn't charge them a dime for its service, instead giving away its language lessons for free, and making it up on volume of ads sold and shown to its users. (Turns out, you can buy a lot of customer loyalty with "free.")
Whatever the reason, today's outage for Duolingo has revealed deep customer love for Duolingo and its product. While Duolingo may not yet be a profitable company, this customer loyalty speaks volumes about the company's growth prospects and suggests the stock is on the right path to success.