I have edited the size several times.
Currently 1200x627 which came from
Social Media FAQ #4 pic related.
I am not on any social media -- so if you know better, bring the sauce and we'll update.
I was rigid about 1200x600 twats for a long time, then added Insta + FB square size 1600x1600 more recently and relaxed my personal standard, currently making graphics in all sizes and shapes but no dimension greater than about 1800 pixels.
There are many anons who would really, REALLY, like to know by trial and error the best sizes for memes. And there are many who simply don't care and won't follow any guidelines suggested. I won't criticize them or scale back their efforts, although sometimes if an extremely large file is provided, I will shrink it to a reasonable file size using one or more of several tools.
Open to discussion & learning & adaptation!