I like this add-on but I confirm it unfortunately has a memory leak, leads to firefox freezing up and sometimes crashing...

Best!
It has the same UI and features of Web Activity tracker on Chrome Web Store. Love it!

It has memory leak. After an hour, it consumes my 8 GB ram.

This is great! Very clean but feature rich. I was using a similar firefox plugin about 10 years ago. To my pleasant surprise this is better and has more features. (Sometimes software gets worse over time, bloated, won't do the main thing well)

This one I think I might keep using long term. I like how it shows your usage data but doesn't overwhelm with more of that then you need. And the limits and notifications are easy to set up. (Though I guess granting access to notifications as a separate step is necessary :-/ ) And I like that you have both.

My only complaint is a feature request: Sometimes the page I get limited on is something I want to keep track of or see again. But currently it seems the limit page doesn't show where you were (except the general domain) so the only way to get back would be to turn the whole add-on off than go back in browser/history. Would be a nice feature to have the limit page list the full URL of the page it blocked so in 24hrs you could revisit and save to bookmark (I use onetab add-on to collect my history). Does that make sense? Just the URL gets kept on that page so you don't lose it.

Thanks for making the add-on. I like it!

-----
Sorry to reply slow:
I was thinking that on the block page itself, no need for a pop-up. The blocked page would say "Time limit
You've reached today your limit on twitter.com
Your current daily limit is 00h : 10m
at the URL twitter.com/theaddressofhtepageIwasviewingwhenthetimerreached10minutes.html"

----------------
further update

I am now having a problem now that the blocking and notification is unreliable. For example right now I have it blocking twitter.com and the time is used up for today but the page is not blocked. In the Time chart it has the eye so it is recognising I have twitter.com open. But the timer is stopped. And the page is usable, not blocked.

I did do the permission.

I did some testing and this is what I found.

I have a notification 5 minutes before the Limit. I noticed the timer stops at the notification time instead of advancing to the Limit time. So I tested by deleting the notification.

That worked! And the timer proceeded and the page was blocked at the limit time.

I had a theory that my adblock was stopping the popup notification, then the FTT was getting stuck. So I created a notification and disable adblock on that URL. What happened was the timer stopped and there was no notification. So, I think the notifications are just broken and it is not related to adblock?

Too bad. For a workaround I guess I will not have notifications. But that is disappointing as that is a good feature. I will update again if I find anything else out.

Fire Time Tracker is a port of excellent Chromium extension Web Activity Time Tracker. It is a well-designed extension which has a good set of features, sports a stylish and snappy GUI and offers export to CSV. So far I have not found a better Firefox extension for time tracking. A good addition might be export to HTML.