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Validate XML or Parse XML to JS/JSON and vise versa rapidly without C/C++ based libraries and no callback

**Note**: If you are using v3, your code may start failing in parsing and validation both. I apologize for the breaking changes. But code was supposed to be changed to support large files and many other options. Please refer the code example below for more detail.

You can use this library online (press try me button above), or as command from CLI, or in your website, or in npm repo.
  • This library let you validate the XML data syntactically.
  • Or you can transform/covert/parse XML data to JS/JSON object.
  • Or you can transform the XML in traversable JS object which can later be converted to JS/JSON object.

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Main Features

  • Works with node packages, in browser, and in CLI
  • Faster than any pure JS implementation.
  • It can handle big files (tested up to 100mb).
  • You can parse CDATA as separate property.
  • You can prefix attributes or group them to separate property. Or can ignore them from result completely.
  • You can parse tag's or attribute's value to premitive type: string, integer, float, or boolean. And can optionally decode for HTML char.
  • You can remove namespace from tag or attribute name while parsing
  • It supports boolean attributes, if configured.

How to use


$npm install fast-xml-parser

or using yarn

$yarn add fast-xml-parser


var fastXmlParser = require('fast-xml-parser');
var jsonObj = fastXmlParser.parse(xmlData);

/* upto 2.9.x
var options = {
    attrPrefix : "@_",
    attrNodeName: false,
    textNodeName : "#text",
    ignoreNonTextNodeAttr : true,
    ignoreTextNodeAttr : true,
    ignoreNameSpace : true,
    ignoreRootElement : false,
    textNodeConversion : true,
    textAttrConversion : false,
    arrayMode : false
//from 3.0.0
var options = {
    attributeNamePrefix : "@_",
    attrNodeName: "attr", //default is 'false'
    textNodeName : "#text",
    ignoreAttributes : true,
    ignoreNameSpace : false,
    allowBooleanAttributes : false,
    parseNodeValue : true,
    parseAttributeValue : false,
    trimValues: true,
    decodeHTMLchar: false,
    cdataTagName: "__cdata", //default is 'false'
    cdataPositionChar: "\\c",
if(fastXmlParser.validate(xmlData)=== true){//optional
	var jsonObj = fastXmlParser.parse(xmlData,options);

//Intermediate obj
var tObj = fastXmlParser.getTraversalObj(xmlData,options);
var jsonObj = fastXmlParser.convertToJson(tObj,options);


  • attributeNamePrefix : prepend given string to attribute name for identification
  • attrNodeName: (Valid name) Group all the attributes as properties of given name.
  • ignoreAttributes : Ignore attributes to be parsed.
  • ignoreNameSpace : Remove namespace string from tag and attribute names.
  • allowBooleanAttributes : a tag can have attributes without any value
  • parseNodeValue : Parse the value of text node to float, integer, or boolean.
  • parseAttributeValue : Parse the value of an attribute to float, integer, or boolean.
  • trimValues : trim string values of an attribute or node
  • decodeHTMLchar : decodes any named and numerical character HTML references excluding CDATA part.
  • cdataTagName : If specified, parser parse CDATA as nested tag instead of adding it's value to parent tag.
  • cdataPositionChar : It'll help to covert JSON back to XML without loosing CDATA position.

To use from command line

$xml2js [-ns|-a|-c|-v|-V] <filename> [-o outputfile.json]
$cat xmlfile.xml | xml2js [-ns|-a|-c|-v|-V] [-o outputfile.json]
  • -ns : To include namespaces (bedefault ignored)
  • -a : To ignore attributes
  • -c : To ignore value conversion (i.e. "-3" will not be converted to number -3)
  • -v : validate before parsing
  • -V : only validate

To use it on webpage

  1. Download and include parser.js Or use directly from CDN
var result = parser.validate(xmlData);
if(result !== true) cnosole.log(result.err);
var jsonObj = parser.parse(xmlData);

JSON or JS Object to XML

var Parser = require("fast-xml-parser").j2xParser;
//default options need not to set
var defaultOptions = {
    attributeNamePrefix : "@_",
    attrNodeName: "@", //default is false
    textNodeName : "#text",
    ignoreAttributes : true,
    encodeHTMLchar: false,
    cdataTagName: "__cdata", //default is false
    cdataPositionChar: "\\c",
    format: false, 
    indentBy: "  ",
    supressEmptyNode: false
var parser = new Parser(defaultOptions);
var xml = parser.parse(json_or_js_obj);


  • attributeNamePrefix : Identify attributes with this prefix otherwise treat them as a tag.
  • attrNodeName: Identify attributes when they are grouped under single property.
  • ignoreAttributes : Don't check for attributes. Treats everything as tag.
  • encodeHTMLchar : encodes values (except cdata values) when writing to XML.
  • cdataTagName : If specified, parse matching tag as CDATA
  • cdataPositionChar : Identify the position where CDATA tag should be placed. If it is blank then CDATA will be added in the last of tag's value.
  • format : If set to true, then format the XML output.
  • indentBy : indent by this char when format is set to true
  • supressEmptyNode : If set to true, tags with no value (text or nested tags) are written as self closing tags.


I decided to created this library when I couldn't find any library which can convert XML data to json without any callback and which is not based on any C/C++ library.

Libraries that I compared

  • xml-mapping : fast, result is not satisfactory
  • xml2js : fast, result is not satisfactory
  • xml2js-expat : couldn't test performance as it gives error on high load. Installation failed on travis and on my local machine using 'yarn'.
  • xml2json : based on node-expat which is based on C/C++. Installation failed on travis.
  • fast-xml-parser : very very fast.

Why not C/C++ based libraries? Installation of such libraries fails on some OS. You may require to install missing dependency manually.

Benchmark report

file size fxp 3.0 validator (rps) fxp 3.0 parser (rps) xml2js 0.4.19 (rps)
1.5k 16581.06758 14032.09323 4615.930805
1.5m 14918.47793 13.23366098 5.90682005
13m 1.834479235 1.135582008 -1
1.3k with CDATA 30583.35319 43160.52342 8398.556349
1.3m with CDATA 27.29266471 52.68877009 7.966000795
1.6k with cdata,prolog,doctype 27690.26082 41433.98547 7872.399268
98m 0.08473858148 0.2600104004 -1
  • -1 indicates error or incorrect output.



Benchmark for JSON to XML

file size fxp 3.2 js to xml xml2js 0.4.19 builder
1.3k 160148.9801 10384.99401
1.1m 173.6374831 8.611884025


Changes from v3

  • It can handle big file now (I have tested up to 98mb). Performance report is given above.
  • Meaningful error messages from validator
"err": {
    "code": "InvalidAttr",
    "msg": "Attributes for rootNode have open quote"
  • Updated options : check snippet aboove
  • Parse boolean values as well. E.g. "true" to true
  • You can set pasrer not to trim whitespaces from attribute or tag /node value.
  • You can set pasrer to HTML decode Tag / node and attribute values. However CDATA value will not be HTML decoded.
  • Tag / node value will not be parsed if CDATA presents.
  • You can set validator and parser to allow boolean values.
  • Few validation and parsing bugs are also fixed

Worth to mention

  • stubmatic : A stub server to mock behaviour of HTTP(s) / REST / SOAP services.
  • fastify-xml-body-parser : Fastify plugin / module to parse XML payload / body into JS object using fast-xml-parser.
  • fast-lorem-ipsum : Generate lorem ipsum words, sentences, paragraph very quickly.
  • Grapes : Flexible Regular expression engine which can be applied on char stream. (under development)


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