It was designed for backward compatibility with ASCII: the first 128 characters of Unicode, which correspond one-to-one with ASCII, are encoded using a single byte with the same binary value as ASCII, so that valid ASCII text is valid UTF-8-encoded Unicode as well. Code points with lower numerical values, which tend to occur more frequently, are encoded using fewer bytes. UTF-8 is capable of encoding all 1,112,064 valid character code points in Unicode using one to four one- byte (8-bit) code units. Defined by the Unicode Standard, the name is derived from Unicode (or Universal Coded Character Set) Transformation Format – 8-bit. UTF-8 is a variable-width character encoding used for electronic communication.