Discerning between Asian texts is actually an easy feat. The major point of confusion arises because written Chinese,Korean and Japanese are highly related having all originated from China.  Fortunately the use the Chinese character system did not perfectly fit with spoken Japanese or Korean.  As such both Japanese and Korean have adopted the writing system to their benefit, a fact that can be used to allow one to tell them apart without being able to read them.

The differences can be summed up as such; that Chinese is heavy and messy, that Korean looks alien like and that Japanese is lighter, sometimes much lighter, than Chinese.

You’d be forgiven if you thought that ‘alien like’ and ‘lighter’ are too subjective to be useful.  My use of these terms is by no means scientific nor standard, but it is descriptive, and likely a bit derogatory. Fear not, a more complete and useful description is provided later, but first I should explain to more depth.

Since Chinese is the basis from which Korean and Japanese have evolved it would be logical to start with it.

范丽青：前两天已经公布过一个两岸新增航点以及春节增加航班班次的新闻。尽管春运期间空运资源异常紧张，而且京沪穗深的机场也异常繁忙，但是大陆民航业务主管部门还是想方设法来尽量满足两岸同胞春节期间往返两岸走亲访友和旅游休闲对航空的需求。 Courtesy of  news.workercn.cn

Notice how ‘cluttered’ or ‘dense the text is. Beyond that there is not anything discernable about Chinese other than it is not Japanese or Korean. Someone with an understanding of the characters would of course take issue with my description since a more accurate term would be ‘detailed’.

Now compare the density of Chinese with the light, less dense, text of Japanese.

通常必殺技をはるかに上回る威力を持つ、スーパーコンボ。これよりも強力な超必殺技が、”ウルトラコンボ”だ！　今回入手した写真は、リュウのウルトラコンボ。ド派手な演出からくり出される波動拳の強化版といったところだろうか。体力ゲージが一気に半分くらい減っている点も見逃せない！ Courtesy of Famitsu.com

The important factor is that Japanese uses both the Chinese characters and the かな, whiten in the Roman alphabet as ‘kana’.  The kana are extreme simplifications of certain Chinese characters and instead of carrying meanings as the Chinese characters do, they represent sounds, much like the English Alphabet. They are used for Japanese invented words and words from for foreign languages such as English. The kana are thin and comparable to the English alphabet in density. A general rule of thumb for telling Japanese apart from Chinese is to look for areas of high density, the Chinese characters, followed by areas of light density, the kana.  To achieve a better understanding you will likely have to study the kana, it is not hard to learn them but it is a bit pointless unless you are also studying Japanese as a whole.

Finally last and the easiest, Korean.

복수노조 허용 및 전임자 임금지급 금지 등 노조법을 두고 30일 국회 환경노동위원회에서는 고성이 오가는 등 몸싸움이 벌어졌다.  Courtesy of chosun.com

Notice how alien like it is? Okay so you’ll likely want something a bit more concrete, that’s perfect, because such a thing exists. Written Korean contains circles. If you can remember that then you are set. Neither Chinese nor Japanese texts will ever contain circles. In fact the closest thing Chinese and Japanese have for circles, are squares. This is caused by stroke rules which do not allow the curves needed to make a circle. Convenient eh?

So perhaps a more complicated yet more useful general rule would be that Japanese has periods of density followed by less dense areas, that Korean contains circles and that Chinese is neither Japanese nor Korean.