Thus the replacement character is now only seen for encoding errors, such as invalid UTF-8.

Consider a text file containing the German word für (meaning 'for') in the ISO-8859-1 encoding (0x66 0xFC 0x72). This file is now opened with a text editor that assumes the input is UTF-8. The first and last byte are valid UTF-8 encodings of ASCII, but the middle byte (0xFC) is not a valid byte in UTF-8. Therefore, a text editor could replace this byte with the replacement character symbol to produce a valid string of Unicode code points. The whole string now displays like this: "f�r".