URLSearchParams

Baseline Widely available *

This feature is well established and works across many devices and browser versions. It’s been available across browsers since ⁨April 2018⁩.

* Some parts of this feature may have varying levels of support.

Note: This feature is available in Web Workers.

The URLSearchParams interface defines utility methods to work with the query string of a URL.

URLSearchParams objects are iterable, so they can directly be used in a for...of structure to iterate over key/value pairs in the same order as they appear in the query string, for example the following two lines are equivalent:

for (const [key, value] of mySearchParams) {
}
for (const [key, value] of mySearchParams.entries()) {
}

Although URLSearchParams is functionally similar to a Map, when iterating, it may suffer from some pitfalls that Map doesn't encounter due to how it's implemented.

Constructor

URLSearchParams(): Returns a URLSearchParams object instance.

Instance properties

size Read only: Indicates the total number of search parameter entries.

Instance methods

URLSearchParams[Symbol.iterator](): Returns an iterator allowing iteration through all key/value pairs contained in this object in the same order as they appear in the query string.
URLSearchParams.append(): Appends a specified key/value pair as a new search parameter.
URLSearchParams.delete(): Deletes search parameters that match a name, and optional value, from the list of all search parameters.
URLSearchParams.entries(): Returns an iterator allowing iteration through all key/value pairs contained in this object in the same order as they appear in the query string.
URLSearchParams.forEach(): Allows iteration through all values contained in this object via a callback function.
URLSearchParams.get(): Returns the first value associated with the given search parameter.
URLSearchParams.getAll(): Returns all the values associated with a given search parameter.
URLSearchParams.has(): Returns a boolean value indicating if a given parameter, or parameter and value pair, exists.
URLSearchParams.keys(): Returns an iterator allowing iteration through all keys of the key/value pairs contained in this object.
URLSearchParams.set(): Sets the value associated with a given search parameter to the given value. If there are several values, the others are deleted.
URLSearchParams.sort(): Sorts all key/value pairs, if any, by their keys.
URLSearchParams.toString(): Returns a string containing a query string suitable for use in a URL.
URLSearchParams.values(): Returns an iterator allowing iteration through all values of the key/value pairs contained in this object.

Examples

Using URLSearchParams

const paramsString = "q=URLUtils.searchParams&topic=api";
const searchParams = new URLSearchParams(paramsString);

// Iterating the search parameters
for (const p of searchParams) {
  console.log(p);
}

console.log(searchParams.has("topic")); // true
console.log(searchParams.has("topic", "fish")); // false
console.log(searchParams.get("topic") === "api"); // true
console.log(searchParams.getAll("topic")); // ["api"]
console.log(searchParams.get("foo") === null); // true
console.log(searchParams.append("topic", "webdev"));
console.log(searchParams.toString()); // "q=URLUtils.searchParams&topic=api&topic=webdev"
console.log(searchParams.set("topic", "More webdev"));
console.log(searchParams.toString()); // "q=URLUtils.searchParams&topic=More+webdev"
console.log(searchParams.delete("topic"));
console.log(searchParams.toString()); // "q=URLUtils.searchParams"

Search parameters can also be an object.

const paramsObj = { foo: "bar", baz: "bar" };
const searchParams = new URLSearchParams(paramsObj);

console.log(searchParams.toString()); // "foo=bar&baz=bar"
console.log(searchParams.has("foo")); // true
console.log(searchParams.get("foo")); // "bar"

Parsing window.location

Unlike URL, the Location interface does not provide a readily-available searchParams property. We can parse location.search with URLSearchParams.

// Assume page has location:
// https://developer.mozilla.org/en-US/docs/Web/API/URLSearchParams?foo=a
const paramsString = window.location.search;
const searchParams = new URLSearchParams(paramsString);
console.log(searchParams.get("foo")); // a

Duplicate search parameters

const paramStr = "foo=bar&foo=baz";
const searchParams = new URLSearchParams(paramStr);

console.log(searchParams.toString()); // "foo=bar&foo=baz"
console.log(searchParams.has("foo")); // true
console.log(searchParams.get("foo")); // bar, only returns the first value
console.log(searchParams.getAll("foo")); // ["bar", "baz"]

No URL parsing

The URLSearchParams constructor does not parse full URLs. However, it will strip an initial leading ? off of a string, if present.

const paramsString1 = "http://example.com/search?query=%40";
const searchParams1 = new URLSearchParams(paramsString1);

console.log(searchParams1.has("query")); // false
console.log(searchParams1.has("http://example.com/search?query")); // true

console.log(searchParams1.get("query")); // null
console.log(searchParams1.get("http://example.com/search?query")); // "@" (equivalent to decodeURIComponent('%40'))

const paramsString2 = "?query=value";
const searchParams2 = new URLSearchParams(paramsString2);
console.log(searchParams2.has("query")); // true

const url = new URL("http://example.com/search?query=%40");
const searchParams3 = new URLSearchParams(url.search);
console.log(searchParams3.has("query")); // true

Percent encoding

URLSearchParams objects percent-encode anything in the application/x-www-form-urlencoded percent-encode set (which contains all code points except ASCII alphanumeric, *, -, ., and _), and encode U+0020 SPACE as +. However, it only handles percent-encoding when serializing and deserializing full URL search params syntax. When interacting with individual keys and values, you always use the unencoded version.

// Creation from parsing a string: percent-encoding is decoded
const params = new URLSearchParams("%24%25%26=%28%29%2B");
// Retrieving all keys/values: only decoded values are returned
console.log([...params]); // [["$%&", "()+"]]
// Getting an individual value: use the decoded key and get the decoded value
console.log(params.get("$%&")); // "()+"
console.log(params.get("%24%25%26")); // null
// Setting an individual value: use the unencoded key and value
params.append("$%&$#@+", "$#&*@#()+");
// Serializing: percent-encoding is applied
console.log(params.toString());
// "%24%25%26=%28%29%2B&%24%25%26%24%23%40%2B=%24%23%26*%40%23%28%29%2B"

If you append a key/value pair with a percent-encoded key, that key is treated as unencoded and is encoded again.

const params = new URLSearchParams();

params.append("%24%26", "value");
params.toString(); // "%2524%2526=value"

Preserving plus signs

The URLSearchParams constructor interprets plus signs (+) as spaces, which might cause problems. In the example below, we use hexadecimal escape sequences to mimic a string containing binary data (where every byte carries information) that needs to be stored in the URL search params. Note how the encoded string produced by btoa() contains + and isn't preserved by URLSearchParams.

const rawData = "\x13à\x17@\x1F\x80";
const base64Data = btoa(rawData); // 'E+AXQB+A'

const searchParams = new URLSearchParams(`bin=${base64Data}`); // 'bin=E+AXQB+A'
const binQuery = searchParams.get("bin"); // 'E AXQB A', '+' is replaced by spaces

console.log(atob(binQuery) === rawData); // false

Never construct URLSearchParams objects using dynamically interpolated strings. Instead, use the append() method, which as mentioned above, interprets all characters as-is.

const rawData = "\x13à\x17@\x1F\x80";
const base64Data = btoa(rawData); // 'E+AXQB+A'

const searchParams = new URLSearchParams();
searchParams.append("bin", base64Data); // 'bin=E%2BAXQB%2BA'
const binQuery = searchParams.get("bin"); // 'E+AXQB+A'

console.log(atob(binQuery) === rawData); // true

Interaction with URL.searchParams

The URL.searchParams property exposes the URL's search string as a URLSearchParams object. When updating this URLSearchParams, the URL's search is updated with its serialization. However, URL.search encodes a subset of characters that URLSearchParams does, and encodes spaces as %20 instead of +. This may cause some surprising interactions—if you update searchParams, even with the same values, the URL may be serialized differently.

const url = new URL("https://example.com/?a=b ~");
console.log(url.href); // "https://example.com/?a=b%20~"
console.log(url.searchParams.toString()); // "a=b+%7E"
// This should be a no-op, but it changes the URL's query to the
// serialization of its searchParams
url.searchParams.sort();
console.log(url.href); // "https://example.com/?a=b+%7E"

const url2 = new URL("https://example.com?search=1234&param=my%20param");
console.log(url2.search); // "?search=1234&param=my%20param"
url2.searchParams.delete("search");
console.log(url2.search); // "?param=my+param"

Empty value vs. no value

URLSearchParams doesn't distinguish between a parameter with nothing after the =, and a parameter that doesn't have a = altogether.

const emptyVal = new URLSearchParams("foo=&bar=baz");
console.log(emptyVal.get("foo")); // returns ''
const noEquals = new URLSearchParams("foo&bar=baz");
console.log(noEquals.get("foo")); // also returns ''
console.log(noEquals.toString()); // 'foo=&bar=baz'

Specifications

Specification
URL # urlsearchparams

Browser compatibility

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This page was last modified on ⁨Feb 26, 2025⁩ by MDN contributors.

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