XML::Tidy - tidy indenting of XML documents


This documentation refers to version 1.20 of XML::Tidy, which was released on Sun Jul 9 09:43:30:08 -0500 2017.


  use strict;use  warnings;
  use   utf8;use XML::Tidy;

  # create new   XML::Tidy object by loading:  MainFile.xml
  my $tidy_obj = XML::Tidy->new('filename' => 'MainFile.xml');

  #   tidy  up  the  indenting

  #             write out changes back     to  MainFile.xml


This module creates XML document objects (with inheritance from XML::XPath) to tidy mixed-content (i.e., non-data) text node indenting. There are also some other handy member functions to compress and expand your XML document object (into either a compact XML representation or a binary one).



This is the standard Tidy object constructor. Except for the added 'binary' option, it can take the same parameters as an XML::XPath object constructor to initialize the XML document object. These can be any one of:

  'filename' => 'SomeFile.xml'
  'binary'   => 'SomeBinaryFile.xtb'
  'xml'      => $variable_which_holds_a_bunch_of_XML_data
  'ioref'    => $file_InputOutput_reference
  'context'  => $existing_node_at_specified_context_to_become_new_obj


The reload() member function causes the latest data contained in a Tidy object to be re-parsed (which re-indexes all nodes).

This can be necessary after modifications have been made to nodes which impact the tree node hierarchy because XML::XPath's find() member preserves state information which can get out-of-sync.

reload() is probably rarely useful by itself but it is needed by strip() and prune() so it is exposed as a method in case it comes in handy for other uses.


The strip() member function searches the Tidy object for all mixed-content (i.e., non-data) text nodes and empties them out. This will basically unformat any markup indenting.

strip() is used by compress() and tidy() but it is exposed because it is also worthwhile by itself.


The tidy() member function can take a single optional parameter as the string that should be inserted for each indent level. Some examples:

  # Tidy up indenting with default two  (2) spaces per indent level

  # Tidy up indenting with         four (4) spaces per indent level
     $tidy_obj->tidy('    ');

  # Tidy up indenting with         one  (1) tab    per indent level
     $tidy_obj->tidy('tab' );

  # Tidy up indenting with         two  (2) tabs   per indent level

The default behavior is to use two (2) spaces for each indent level. The Tidy object gets all mixed-content (i.e., non-data) text nodes reformatted to appropriate indent levels according to tree nesting depth.

NOTE: tidy() disturbs some XML escapes in whatever ways XML::XPath does. It has been brought to my attention that these modules also strip CDATA tags from XML files / data they operate on. Even though CDATA tags don't seem very common, I would very much like for them to work smoothly too. Hopefully the vast majority of files will work fine and future support for any of the more rare types can be added later.

Additionally, please take notice that every call to tidy() (as well as reload, strip, and most other XML::Tidy functions) leak some memory due to their usage of XPath's findnodes command. This issue was described helpfully at HTTPS://RT.CPAN.Org/Ticket/Display.html?id=120296. Thanks to Jozef!


The compress() member function calls strip() on the Tidy object then creates an encoded comment which contains the names of elements and attributes as they occurred in the original document. Their respective element and attribute names are replaced with just the appropriate index throughout the document.

compress() can accept a parameter describing which node types to attempt to shrink down as abbreviations. This parameter should be a string of just the first letters of each node type you wish to include as in the following mapping:

  e = elements
  a = attribute   keys
  v = attribute values *EXPERIMENTAL*
  t = text       nodes *EXPERIMENTAL*
  c = comment    nodes *EXPERIMENTAL*
  n = namespace  nodes *not-yet-implemented*

Attribute values ('v') and text nodes ('t') both seem to work fine with current tokenization. I've still labeled them EXPERIMENTAL because they seem more likely to cause problems than valid element or attribute key names. I have some bugs in the comment node compression which I haven't been able to find yet so that one should be avoided for now. Since these three node types ('vtc') all require tokenization, they are not included in default compression ('ea'). An example call which includes values and text would be:


The original document structure (i.e., node hierarchy) is preserved. compress() significantly reduces the file size of most XML documents for when size matters more than immediate human readability. expand() performs the opposite conversion.


The expand() member function reads any XML::Tidy::compress comments from the Tidy object and uses them to reconstruct the document that was passed to compress().


The bcompress() member function stores a binary representation of any Tidy object. The format consists of:

  0) a null-terminated version string
  1) a byte specifying how many bytes later indices will be
  2) the number of bytes from 1 above to designate the total string  count
  3) the number of null-terminated          strings from 2 above
  4) the number of bytes from 1 above to designate the total integer count
  5) the number of 4-byte                  integers from 4 above
  6) the number of bytes from 1 above to designate the total float   count
  7) the number of 8-byte (double-precision) floats from 6 above
  8) node index sets until the end of the file

Normal node index sets consist of two values. The first is an index (again the number of bytes long comes from 1) into the three lists as if they were all linear. The second is a single-byte integer identifying the node type (using standard DOM node type enumerations).

A few special cases exist in node index sets though. If the index is null, it is interpreted as a close-element tag (so no accompanying type value is read). On the other end, when the index is non-zero, the type value is always read. In the event that the type corresponds to an attribute or a processing instruction, the next index is read (without another accompanying type value) in order to complete the data fields required by those node types.

NOTE: Please bear in mind that the encoding of binary integers and floats only works properly if the values are not surrounded by spaces or other delimiters and each is contained in its own single node. This is necessary to enable thorough reconstruction of whitespace from the original document. I recommend storing every numerical value as an isolated attribute value or text node without any surrounding whitespace.

  # Examples which encode all numbers as binary:
  <friend name="goodguy" category="15">

  # Examples which encode all numbers as strings:
  <enemy name="badguy" category=" 666 ">
    <hitpoints> 2.0 </hitpoints>
    <location> 4.0 -2.0 4.0 </location>

The default file extension is .xtb (for XML::Tidy Binary).


The bexpand() member function reads a binary file which was previously written from bcompress(). bexpand() is an XML::Tidy object constructor like new() so it can be called like:

  my $xtbo = XML::Tidy->bexpand('BinaryInputFilename.xtb');


The prune() member function takes an XPath location to remove (along with all attributes and child nodes) from the Tidy object. For example, to remove all comments:


or to remove the third baz (XPath indexing is 1-based):


Pruning your XML tree is a form of tidying too so it snuck in here. =)


The write() member function can take an optional filename parameter to write out any changes to the Tidy object. If no parameters are given, write() overwrites the original XML document file (if a 'filename' parameter was given to the constructor).

write() will croak() if no filename can be found to write to.

write() can also take a secondary parameter which specifies an XPath location to be written out as the new root element instead of the Tidy object's root. Only the first matching element is written.


The toString() member function is almost identical to write() except that it takes no parameters and simply returns the equivalent XML string as a scalar. It is a little weird because normally only XML::XPath::Node objects have a toString() member but I figure it makes sense to extend the same syntax to the parent object as well, since it is a useful option.

createNode Wrappers

The following are just aliases to Node constructors. They'll work with just the unique portion of the node type as the member function name.

e() or el() or elem() or createElement()

wrapper for XML::XPath::Node::Element->new()

a() or at() or attr() or createAttribute()

wrapper for XML::XPath::Node::Attribute->new()

c() or cm() or cmnt() or createComment()

wrapper for XML::XPath::Node::Comment->new()

t() or tx() or text() or createTextNode()

wrapper for XML::XPath::Node::Text->new()

p() or pi() or proc() or createProcessingInstruction()

wrapper for XML::XPath::Node::PI->new()

n() or ns() or nspc() or createNamespace()

wrapper for XML::XPath::Node::Namespace->new()


Since they are sometimes needed to compare against, XML::Tidy also exports the same node constants as XML::XPath::Node (which correspond to DOM values). These include:



















XML::Tidy also exports:


which returns a reasonable default XML declaration string (assuming typical "utf-8" encoding).


- fix reload() from messing up Unicode escaped &XYZ; components like Copyright &#xA9; and Registered &#xAE; (probably needs pre and post processing)
- write many better UTF-8 tests
- support namespaces
- handle CDATA


Revision history for Perl extension XML::Tidy:

- 1.20 H79M9hU8 Sun Jul 9 09:43:30:08 -0500 2017

* removed broken Build.PL to resolve HTTPS://RT.CPAN.Org/Ticket/Display.html?id=122406. (Thank you, Slaven.)

- 1.18 H78M5qm1 Sat Jul 8 05:52:48:01 -0500 2017

* fixed new() to check file or xml to detect standalone in declaration, from HTTPS://RT.CPAN.Org/Ticket/Display.html?id=122389 (Thanks Alex!)

* traced tidy() memory leak from HTTPS://RT.CPAN.Org/Ticket/Display.html?id=120296 (Thanks Jozef!) which seems to come from every XPath->findnodes() call

* aligned synopsis comments

* updated write() to use output encoding UTF-8 since that's what almost all XML should rely on (with thanks to RJBS for teaching me much from his great talk at HTTPS://YouTube.Com/watch?v=TmTeXcEixEg)

* collapsed trailing curly braces on code blocks

* added croak for any failed file open attempt

- 1.16 G6LM4EST Tue Jun 21 04:14:28:29 -0500 2016

* stopped using my old fragile package generation and manually updated all distribution files (though Dist::Zilla should let me generate much again)

* updated license to GPLv3+

* fixed 00pod.t and 01podc.t to eval the Test modules from issue and patch: HTTPS://RT.CPAN.Org/Public/Bug/Display.html?id=85592 (Thanks again MichielB.)

* replaced all old '&&' with 'and' in POD

- 1.14 G6JMERCY Sun Jun 19 14:27:12:34 -0500 2016

* separated old PT from VERSION to fix non-numeric issue: HTTPS://RT.CPAN.Org/Public/Bug/Display.html?id=56073 (Thanks to Slaven.)

* removed Unicode from POD but added encoding utf8 anyway to pass tests and resolve issues: HTTPS://RT.CPAN.Org/Public/Bug/Display.html?id=92434 and HTTPS://RT.CPAN.Org/Public/Bug/Display.html?id=85592 (Thanks to Sudhanshu and MichielB.)

- 1.12.B55J2qn Thu May 5 19:02:52:49 2011

* made "1.0" float binarize as float again, rather than just "1" int

* cleaned up POD and fixed EXPORTED CONSTANTS heads blocking together

- 1.10.B52FpLx Mon May 2 15:51:21:59 2011

* added tests for undefined non-standard XML declaration to suppress warnings

- 1.8.B2AMvdl Thu Feb 10 22:57:39:47 2011

* aligned .t code

* added test for newline before -r to try to resolve: HTTPS://RT.CPAN.Org/Ticket/Display.html?id=65471 (Thanks, Leandro.)

* fixed off-by-one error when new gets a readable (non-newline) filename (that's not "filename" without a pre-'filename' param) to resolve: HTTPS://RT.CPAN.Org/Ticket/Display.html?id=65151 (Thanks, Simone.)

- 1.6.A7RJKwl Tue Jul 27 19:20:58:47 2010

* added head2 POD for EXPORTED CONSTANTS to try to pass t/00podc.t

- 1.4.A7QCvHw Mon Jul 26 12:57:17:58 2010

* hacked a little test for non-UTF-8 decl str to resolve FrankGoss' need for ISO-8859-1 decl encoding to persist through tidying

* md sure META.yml is being generated correctly for the CPAN

* updated license to GPLv3

- 1.2.75BACCB Fri May 11 10:12:12:11 2007

* made "1.0" float binarize as just "1" int

* made ints signed and bounds checked

* added new('binary' => 'BinFilename.xtb') option

- 1.2.54HJnFa Sun Apr 17 19:49:15:36 2005

* fixed tidy() processing instruction stripping problem

* added support for binary ints and floats in bcompress()

* tightened up binary format and added pod

- 1.2.54HDR1G Sun Apr 17 13:27:01:16 2005

* added bcompress() and bexpand()

* added compress() and expand()

* added toString()

- 1.2.4CKBHxt Mon Dec 20 11:17:59:55 2004

* added exporting of XML::XPath::Node (DOM) constants

* added node object creation wrappers (like LibXML)

- 1.2.4CCJW4G Sun Dec 12 19:32:04:16 2004

* added optional 'xpath_loc' => to prune()

- 1.0.4CAJna1 Fri Dec 10 19:49:36:01 2004

* added optional 'filename' => to write()

- 1.0.4CAAf5B Fri Dec 10 10:41:05:11 2004

* removed 2nd param from tidy() so that 1st param is just indent string

* fixed pod errors

- 1.0.4C9JpoP Thu Dec 9 19:51:50:25 2004

* added xplc option to write()

* added prune()

- 1.0.4C8K1Ah Wed Dec 8 20:01:10:43 2004

* inherited from XPath so that those methods can be called directly

* original version (separating from


From the command shell, please run:

  `perl -MCPAN -e "install XML::Tidy"`

or uncompress the package and run the standard:

  `perl Makefile.PL; make; make test; make install`


XML::Tidy requires:

Carp to allow errors to croak() from calling sub

XML::XPath to use XPath statements to query and update XML

XML::XPath::XMLParser to parse XML documents into XPath objects

Math::BaseCnv to handle base-64 indexing for compress() and expand()


Please report any bugs or feature requests to bug-XML-Tidy at RT.CPAN.Org, or through the web interface at HTTPS://RT.CPAN.Org/NoAuth/ReportBug.html?Queue=XML-Tidy. I will be notified, and then you can be updated of progress on your bug as I address fixes.


You can find documentation for this module (after it is installed) with the perldoc command.

  `perldoc XML::Tidy`

You can also look for information at:

    RT: CPAN's Request Tracker


    AnnoCPAN: Annotated CPAN documentation


    CPAN Ratings


    Search CPAN



Most source code should be Free! Code I have lawful authority over is and shall be! Copyright: (c) 2004-2017, Pip Stuart. Copyleft : This software is licensed under the GNU General Public License (version 3 or later). Please consult HTTPS://GNU.Org/licenses/gpl-3.0.txt for important information about your freedom. This is Free Software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. See HTTPS://FSF.Org for further information.


Pip Stuart <Pip@CPAN.Org>