What happened

Duolingo's (DUOL -1.55%) 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?

Simple green arrow going up.

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.

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...

and perhaps a bit panicked...

and eager to see Duolingo come back online soon.

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.