You see it on Japanese forums. Strings of "w's". I often quote individuals as writing "lol", "LOL", or even, "lulz". But let's get something straight. People in Japan do not laugh out loud. Oh, no. They wwww.
Using "w" is not new. Online in Japan, people have been using them for over a decade, which in internet time is since the Stone Age.
The base for "w" is from "warau" (笑う) or "warai" (笑い), the Japanese word for laugh or smile.
The use of "w" has become prevalent online. On Japanese keyboards, it's easy to knock out the letter "w" and you can show the degree of your amusement in online games or on internet forums by writing, for example, "wwwwwwww" or a more enthusiastic "wwwwwwwwwwwwwwwww." What also makes the "w" appealing is also how the letter looks somewhat like an upturned face—a motif echoed in the country's internet meme characters, like "Yaruo" (やる夫, above).
Earlier this month, a columnist in Japan remarked how using "(笑)" instead of "w" might make others happier. The point of the piece was that you can soften jokes in your online communication by using that kanji character.
It was a rather odd thing to write, seeing how more recently, (笑) is used to sneer at those who aren't funny or amusing—an internet slow clap. In a way, it can be similar to the schadenfreude that "lulz" expresses for English speaking net users. Though, "lulz" isn't always ironic.
Japan isn't the only country to have its own version of "lol." Korea has kkk, China 233, and Thailand has 555—among others.  See, everybody's laughing, just not LOL-ing.