Does a valid XML file require an XML declaration

Question

I am parsing an XML file using Sax Parser of Xerces  Is the XML declaration  lt  xml version  1 0  encoding  UTF-8   gt  required

User · Answer

Xml declaration is optional so your xml is well-formed without it  But it is recommended to use it so that wrong assumptions are not made by the parsers  specifically about the encoding used

User · Answer

In XML 1 0  the XML Declaration is optional   See section 2 8 of the XML 1 0 Recommendation  where it says it  should  be used -- which means it is recommended  but not mandatory  In XML 1 1  however  the declaration is mandatory  See section 2 8 of the XML 1 1 Recommendation  where it says  MUST  be used  It even goes on to state that if the declaration is absent  that automatically implies the document is an XML 1 0 document   Note that in an XML Declaration the encoding and standalone are both optional  Only the version is mandatory  Also  these are not attributes  so if they are present they must be in that order  version  followed by any encoding  followed by any standalone    lt  xml version  1 0   gt   lt  xml version  1 0  encoding  UTF-8   gt   lt  xml version  1 0  standalone  yes   gt   lt  xml version  1 0  encoding  UTF-16  standalone  yes   gt    If you don t specify the encoding in this way  XML parsers try to guess what encoding is being used  The XML 1 0 Recommendation describes one possible way character encoding can be autodetected  In practice  this is not much of a problem if the input is encoded as UTF-8  UTF-16 or US-ASCII  Autodetection doesn t work when it encounters 8-bit encodings that use characters outside the US-ASCII range  e g  ISO 8859-1  -- avoid creating these if you can   The standalone indicates whether the XML document can be correctly processed without the DTD or not  People rarely use it  These days  it is a bad to design an XML format that is missing information without its DTD   Update   A  prolog error invalid utf-8 encoding  error indicates that the actual data the parser found inside the file did not match the encoding that the XML declaration says it is  Or in some cases the data inside the file did not match the autodetected encoding   Since your file contains a byte-order-mark  BOM  it should be in UTF-16 encoding  I suspect that your declaration says  lt  xml version  1 0  encoding  UTF-8   gt  which is obviously incorrect when the file has been changed into UTF-16 by NotePad  The simple solution is to remove the encoding and simply say  lt  xml version  1 0   gt   You could also edit it to say encoding  UTF-16  but that would be wrong for the original file  which wasn t in UTF-16  or if the file somehow gets changed back to UTF-8 or some other encoding   Don t bother trying to remove the BOM -- that s not the cause of the problem  Using NotePad or WordPad to edit XML is the real problem

User · Answer

It is only required if you aren t using the default values for version and encoding  which you are in that example

[xml] Does a valid XML file require an XML declaration?

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