The phrase "social giant" refers to a person or company that has a huge influence and presence in the world of social media or social networking platforms. They are highly popular and have a large number of users or followers. Full definition
We can't really ignore this very powerful social giant of the web. (careerdigital.com)
Just the knowledge that I may some day become buddy - buddies with such social giants as Mike Romanoff, John Perona and Henry McLemore cements my allegiance to their association. (si.com)
A number of social giants like Twitter, Facebook and Instagram also make their data available for free online through APIs. (allwork.space)