There are many ways people express laughter online and two of the most common are "lol" and "haha." Facebook has been monitoring the way people laugh online and says "lol" is pretty much dead, having been replaced by "haha." A research team at Facebook has been looking at the way people laugh on the social network since May.
Of all the ways people e-laugh, "haha" is the most common and the second most common is with emoji. The majority of people only use one type of e-laugh, while 20% use two types.
Facebook went as far as to explain the differences between "haha", "hahaha", and "hahahahhhhahahahaha."
The six letter hahaha is also very common, and in general, the hahaers use longer laughter. The hahaers are also slightly more open than the hehe-ers to using odd number of letters, and we do see the occasional hahaas and hhhhaaahhhaas. The lol almost always stands by itself, though some rare specimens of lolz and loll were found. A single emoji is used 50% of the time, and it's quite rare to see people use more than 5 identical consecutive emoji. Perhaps emoji offer a concise way to convey various forms of laughter? - Facebook