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3.12.0 • Public • Published


Validate XML, Parse XML to JS/JSON and vice versa, or parse XML to Nimn rapidly without C/C++ based libraries and no callback

This project welcomes contributors. If you have a feature you'd like to see implemented or a bug you'd liked fixed, the best and fastest way to make that happen is to implement it and submit a PR. Basic knowledge of JS is sufficient. Feel free to ask for any guidance.

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Main Features

FXP logo
  • Validate XML data syntactically
  • Transform XML to JSON or Nimn
  • Transform JSON back to XML
  • Works with node packages, in browser, and in CLI (press try me button above for demo)
  • Faster than any pure JS implementation.
  • It can handle big files (tested up to 100mb).
  • Various options are available to customize the transformation
    • 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 primitive type: string, integer, float, hexadecimal, 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

To use it in NPM package install it first

$npm install fast-xml-parser or using yarn $yarn add fast-xml-parser

To use it from CLI Install it globally with -g option.

$npm install fast-xml-parser -g

To use it on a webpage include it from parser.js or directly from CDN


var jsonObj = parser.parse(xmlData [,options] );
var parser = require('fast-xml-parser');
var he = require('he');
var options = {
    attributeNamePrefix : "@_",
    attrNodeName: "attr", //default is 'false'
    textNodeName : "#text",
    ignoreAttributes : true,
    ignoreNameSpace : false,
    allowBooleanAttributes : false,
    parseNodeValue : true,
    parseAttributeValue : false,
    trimValues: true,
    cdataTagName: "__cdata", //default is 'false'
    cdataPositionChar: "\\c",
    localeRange: "", //To support non english character in tag/attribute values.
    parseTrueNumberOnly: false,
    attrValueProcessor: a => he.decode(a, {isAttributeValue: true}),//default is a=>a
    tagValueProcessor : a => he.decode(a) //default is a=>a
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);

Note: he library is used in this example

XML to Nimn

var nimnData = parser.parse(xmlData, schema [,options] );
//Intermediate obj
var tObj = fastXmlParser.getTraversalObj(xmlData,options);
var jsonObj = fastXmlParser.convertToJson(tObj,options);
//construct schema manually or with the help of schema builder
var nimndata = fastXmlParser.convertTonimn(tObj,schema,options);
  • NIMN (निम्न) reduces size of the data by 80%.
  • Check nimnjs to know more about schema, json to nimndata and reverse transformation.
  • 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 : This options has been removed from 3.3.4. Instead, use tagValueProcessor, and attrValueProcessor. See above example.
  • 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 losing CDATA position.
  • localeRange: Parser will accept non-English character in tag or attribute name. Check #87 for more detail. Eg localeRange: "a-zA-Zа-яёА-ЯЁ"
  • parseTrueNumberOnly: if true then values like "+123", or "0123" will not be parsed as number.
  • tagValueProcessor : Process tag value during transformation. Like HTML decoding, word capitalization, etc. Applicable in case of string only.
  • attrValueProcessor : Process attribute value during transformation. Like HTML decoding, word capitalization, etc. Applicable in case of string only.
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 (by default 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
var result = parser.validate(xmlData);
if(result !== true) console.log(result.err);
var jsonObj = parser.parse(xmlData);

JSON / 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,
    cdataTagName: "__cdata", //default is false
    cdataPositionChar: "\\c",
    format: false,
    indentBy: "  ",
    supressEmptyNode: false,
    tagValueProcessor: a=> he.encode(a, { useNamedReferences: true}),// default is a=>a
    attrValueProcessor: a=> he.encode(a, {isAttributeValue: isAttribute, useNamedReferences: true})// default is a=>a
var parser = new Parser(defaultOptions);
var xml = parser.parse(json_or_js_obj);

With the correct options, you can get the almost original XML without losing any information.

  • 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 : This option has been removed from 3.3.4. Use tagValueProcessor, and attrValueProcessor instead. See above example.
  • 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.
  • tagValueProcessor : Process tag value during transformation. Like HTML encoding, word capitalization, etc. Applicable in case of string only.
  • attrValueProcessor : Process attribute value during transformation. Like HTML encoding, word capitalization, etc. Applicable in case of string only.




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.



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

Worth to mention


List of applications and projects using Fast XML Parser. (Raise an issue to submit yours)


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