Limit - Set Limits for Distracting Sites.
https://chrome.google.com/webstore/detail/limit-set-limits-for-dist/blcdfhbibkkjpfdddnmnmhfgjlicebba
Chrome-based plugin.
I... can recommend it. :P
And I have 9 minutes left on this social media. 😋 I guess I'll check briefly again this evening!
@undefined @trinsec I don't understand why this is a subscription service 
@dimi
Yes, their Freedom app is payware.
But I'm talking about Limit, their free browser plugin. :) That's also listed on their site.
@trinsec I don't use Chrome, so went to their website to find the Firefox addon, and the advertising on their website made me uneasy. It seems like a trap of some sort. There are enough Firefox addons that I'm sure I can find something similar without worrying about unwanted surprises.