There are many apps on the web that provides timer but, first of all you need to open app website and it takes time to start timer. So if we want to use online timer from other website then it will consume more time.
But now Google provides online timer on google search. You can setup timer in Google by adding command of timer in google search bar.
timer for <time> OR set timer for <time>
timer for 1 hour 5 minutes 30 seconds OR set timer for 1 hour 5 minutes 30 seconds
You can also use hour, minute and second in timer option, as per your requirement.