The threshold for most people is slightly lower than a quarter second, but it's certainly the case that above a quarter-second users will notice the delay[0].

The threshold for most people is slightly lower than a quarter second, but it's certainly the case that above a quarter-second users will notice the delay[0]. However, people may be primed for longer delays still seeming instant. e.g. Smartphones for many years had a built-in 300ms delay on any click event, and even without that event typically still have delays on many 'instant' actions. So while the delay will be registered as being present, it may not be registered as "this site is slow" but "it's just a natural delay". [0] https://psychology.stackexchange.com/questions/1664/what-is-the-threshold-where-actions-are-perceived-as-instant https://psychology.stackexchange.com/questions/1664/what-is-...