What do you think about double-clicking in web apps?

I've struggled with this while building a desktop app for an internal test team way back when...

While it was a different application and environment, I ended up applying both single click and double click on a specific element in the user interface(the most visible element).

We produced training videos and documentation for users to be able to use the tool with minium effort. That said, it was an ultra specific in-house testing tool with a very dedicated focus (i.e. there weren't a whole lot of actions for a user to take in order to use the tool).

In the end, the tool and the interface was well received. Yet, even after a year of it being used, most users seemed unaware about the double-click functionality. When I asked people about it, the general response was that since single click was present in the app, there was no expectation of a double click option. It almost became like an easter egg. Any time I did a webinar for new and existing employees, there was was always an 'ahh I didn't know you could also double click' comment...

So, moral of the story, for me, was to KISS and avoid double-clicks. Not saying don't implement it, but KISS is KISSS is KISS. :-D

In a browser, I only double click to select a word and I expect it o be consistent on every page I go to.

I think it's fine as long as the context around the action has already been established elsewhere eg desktop OS. In Google drive I often double click on folders which does exactly what you'd expect: take me into the folder.

But I think I'd get annoyed if some vague functionality was only accessible through a double click.

I've got to say, I've never even thought about this - it's amazing how you subconsciously use products and don't think about how you use them

If I'm in a web browser, I never double click.

For things like folders, I would expect it to expand on a single click