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Difference Between UCS-2 and UTF-16

UCS-2 vs UTF-16

UCS-2 and UTF-16 are two character encoding schemes that use 2 bytes, which consists of 16 bits, to represent each character; thus the 2 and 16 suffixes. The main difference between UCS-2 and UTF-16 is which one is being used today. UCS-2 is an older scheme that has since been considered obsolete and replaced with the much newer and more powerful UTF-16.

UCS-2 is a fixed width encoding that uses two bytes for each character; meaning, it can represent up to a total of 216 characters or slightly over 65 thousand. On the other hand, UTF-16 is a variable width encoding scheme that uses a minimum of 2 bytes and a maximum of 4 bytes for each character. This lets UTF-16 represent any character in Unicode while using minimal space for the most commonly used characters. For majority of the 65,000+ characters, UCS-2 and UTF-16 have identical code points; so they are largely equivalent. This lets UTF-16 capable applications to correctly interpret UCS-2 codes. But the other way around would not work due to the many enhancements in UTF-16.

One of the said enhancements is the ability to represent scripts that go from right to left rather than from left to right. In UTF-16 the scripts can identify directionality, thus allowing the application to correctly render the words that are stored in the code. UCS-2 lacks this ability thus will not work with scripts like Arabic and Hebrew, which move from right to left. Another feature that UTF-16 has is normalization. Normalization treats words that mean the same thing but are represented differently as identical. For example, the words “cannot” and “can’t” are identical since the latter is just a contraction of the former. This is very important, especially when you are searching for such words, as it would allow for a more comprehensive search result. In UCS-2, this does not occur automatically, so the application needs to implement such a feature on its own.

There is really no reason to choose UCS-2 over UTF-16, aside from having an application you need not supporting UTF-16. In all aspects, UTF-16 is superior to UCS-2. It is also largely backwards compatible, so you do not have to worry about files encoded in UCS-2.


  1. UCS-2 is obsolete and has since been replaced with UTF-16
  2. UCS-2 is a fixed width encoding scheme while UTF-16 is a variable width encoding scheme
  3. UTF-16 capable applications can read UCS-2 files but not the other way around
  4. UTF-16 supports right to let scripts while UCS-2 does not
  5. UTF-16 supports normalization while UCS-2 does not

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