How to remove URL from query string?

When working with URLs and query strings, you may sometimes need to remove the URL portion and be left only with the query string. The query string contains additional parameters passed along with the URL and is separated by a question mark (?). Removing the URL is a common requirement when you only need to work with the query parameters and values.

What is a URL query string?

A URL query string is made up of additional parameters added after the main URL separated by a question mark (?). It has a key=value format for each parameter it contains. For example:

www.example.com?key1=value1&key2=value2

Here the main URL is www.example.com and the query string contains two parameters – key1 with a value of value1 and key2 with a value of value2. The & symbol separates each key/value pair in the query string.

The query string allows passing additional data along with the URL and is commonly used to send data to web servers on form submissions and API calls. It is appended to the end of the base URL and everything after the ? is considered part of the query string.

Why remove the URL from the query string?

There are a few common reasons you may want to extract just the query string from a full URL:

To parse through and work with the query parameters and values separately from the base URL.
To pass just the string of parameters to another function or API call.
To log or display only the query string data for analysis.

To reconstruct a URL with a different base URL but keep same query parameters.

By removing the base URL, you are left with only the useful query string content to utilize in various ways. The base URL may not always be needed, so extracting it out simplifies working with just the query data.

Approaches to remove URL from query string

There are a few approaches that can be used to extract the query string out from a full URL:

Using built-in URL/URI methods

Most languages and platforms provide URL/URI parsing methods out of the box that can be used:

JavaScript – can use the URLSearchParams() and searchParams property of the URL API.
Python – can use the urllib.parse.urlparse() method.

Java – can use the java.net.URI class.
PHP – can use parse_url() and check the ‘query’ key.

These methods split the URL into components and return the query string in a simple way. For example:


// JavaScript

let url = 'https://www.example.com/path?foo=bar&x=42';
let searchParams = new URL(url).searchParams;

// Python  

from urllib.parse import urlparse

url = 'https://www.example.com/path?foo=bar&x=42' 
query_string = urlparse(url).query

// Java

import java.net.*;

URI uri = new URI("https://www.example.com/path?foo=bar&x=42");
String query = uri.getQuery();

// PHP

$url = 'https://www.example.com/path?foo=bar&x=42';
$queryString = parse_url($url, PHP_URL_QUERY);

This makes extracting the query string simple with just built-in methods.

Regular expression search

Another option is using a regular expression search to look for the query string portion of the URL. A basic regular expression like /\?(.*)/ can be used to match on any query params after a ? symbol.

For example:


// JavaScript

let url = 'https://www.example.com/path?foo=bar&x=42';
let matches = url.match(/\?(.*)/);
let queryString = matches[1]; 

// Python

import re

url = 'https://www.example.com/path?foo=bar&x=42'
match = re.search(r'\?(.*)', url)
query_string = match.group(1)

// Java

String url = "https://www.example.com/path?foo=bar&x=42";
Pattern pattern = Pattern.compile("\\?(.*)");
Matcher matcher = pattern.matcher(url);

String queryString = "";
if(matcher.find()) {
  queryString = matcher.group(1);
} 

// PHP

$url = 'https://www.example.com/path?foo=bar&x=42';
preg_match('/\?(.*)/', $url, $matches);
$queryString = $matches[1];

The regular expression provides a flexible way to extract the query string across languages.

Splitting on the ? symbol

A simpler approach in some cases is to just split the URL on the ? symbol which always precedes the start of the query string.

  
// JavaScript 

let url = 'https://www.example.com/path?foo=bar&x=42';
let parts = url.split('?');
let queryString = parts[1];

// Python

url = 'https://www.example.com/path?foo=bar&x=42'  
query_string = url.split('?')[1]

// Java

String url = "https://www.example.com/path?foo=bar&x=42";
String[] parts = url.split("\\?");
String queryString = parts[1];

// PHP

$url = 'https://www.example.com/path?foo=bar&x=42';
$parts = explode('?', $url);
$queryString = $parts[1];

A split on the delimiter is a quick way to access the query string part directly.

Key Points

To recap, some key points on removing the URL and extracting just the query string:

The query string in a URL carries key/value parameters and is separated by a ? symbol.
Built-in URL/URI parser methods provide an easy way to access the query string.

Regular expressions can search for text after the ? symbol.
Splitting on the ? symbol divides the URL into pre and post query string.
The query string portion can be used independently for additional processing and parsing.

Example Function

Here is an example function that demonstrates how to extract the query string from a URL using a regular expression:


function getQueryString(url) {
  let regex = /\?(.*)/; 
  let matches = url.match(regex);

  if(!matches) {
    return '';
  }

  return matches[1]; 
}

let testUrl = 'https://www.example.com/path?foo=bar&x=42';

let queryString = getQueryString(testUrl);

console.log(queryString); // Logs 'foo=bar&x=42'

This reusable function takes a full URL, runs a regular expression match to extract the query string portion, and returns it. It demonstrates a straightforward way to isolate the query params from the base URL.

Use Cases

Some examples of where removing the URL and keeping just the query string is useful:

Parsing/handling form data – When submitting forms, you can extract just the form data in the query string for processing.
URL shortener services – To create a shortened URL, the query portion can be preserved while changing the base URL.
APIs/web hooks – APIs may return a URL with query parameters to communicate data that needs extracted.

Web analytics – The query data can provide insights into usage parameters for analysis.

The query string contains meaningful information in many cases where the base URL is less important. Pulling it out allows focusing on just the key/values in the string.

Conclusion

Extracting the query string away from the full URL is a common requirement for further processing and usage of the query data. Built-in parser methods provide an easy way to access it directly. Regular expressions give a flexible approach across languages. And split methods can divide the URL conveniently on the ? delimiter.

Understanding the various options to isolate the query string allows easily removing the base URL when only the query parameters are needed. This simplifies handling use cases where leveraging the query data independently provides value.