I use localStorage and need to know how my website behaves when there is no storage left on user's device (or at least browser denies access to storage with a quota exceeded).
Is there any way (other than filling my device with files) to simulate a "quota exceeded error"? It seems the reason why many users can't access my website.
Some browsers let the user enter local storage limits. Try setting a really low limit.
See this.
A different approach could be to “fill up” local storage before your application starts, to simulate a full storage.