The set() method of the URLSearchParams interface sets the value associated with a given search parameter to the given value. If there were several matching values, this method deletes the others. If the search parameter doesn't exist, this method creates it.

Note: This feature is available in Web Workers.


URLSearchParams.set(name, value)


The name of the parameter to set.
The value of the parameter to set.

Return value



Let's start with a simple example:

let url = new URL('https://example.com?foo=1&bar=2');
let params = new URLSearchParams(url.search);

//Add a third parameter.
params.set('baz', 3);
params.toString(); // "foo=1&bar=2&baz=3"

Below is a real-life example demonstrating how to create a URL and set some search parameters.

You can copy and paste the example in a code environment like Codepen, JSFiddle, or the multi-line JavaScript interpreter in Firefox.

  • line #41: Comment out this line to stop dumping the search parameters to the console (debug()).
  • line #43: Dumps the generated object and its string representation to the console (info()).
  • line #44: Tries to automatically open a new window/tab with the generated URL (when uncommented).
'use strict'

function genURL(rExp, aText, bDebug=false){
	let theURL

	theURL= new URL('https://regexr.com')
	theURL.searchParams.set( 'expression', rExp.toString() )
	theURL.searchParams.set( 'tool', 'replace' )
	theURL.searchParams.set( 'input', '\u2911\u20dc' )// ⤑⃜
	theURL.searchParams.set( 'text', aText.join('\n') )
	if( bDebug ){
		// Display the key/value pairs
		for(var pair of theURL.searchParams.entries()) {
			console.debug(pair[0] + ' = \'' + pair[1] + '\'');
	return theURL
var url = genURL(
	/(^\s*\/\/|\s*[^:]\/\/).*\s*$|\s*\/\*(.|\n)+?\*\/\s*$/gm	// single/multi-line comments
	// /(^\s*\/\/.*|\s*[^:]\/\/.*)/g								// single-line comments
		"These should work:",
		"// eslint-disable-next-line no-unused-vars",
		"lockPref(	'keyword.URL',\t\t'https://duckduckgo.com/html/?q=!+'	)\t//      test",
		"	* bla bla    ",
		"/* bla bla */",
		"// bla bla ",
		"These shouldn\'t work:",
		"var url = \"http://regexr.com/foo.html?q=bar\"",
	, true
console.info( url, url.toString() )
// window.open( url, 'regex_site' )


Specification Status Comment
The definition of 'set()' in that specification.
Living Standard Initial definition.

Browser compatibility

BCD tables only load in the browser