URL Query String Parser
Supported Input Formats
- URL: Full URL (e.g., https://example.com?id=123)
- Query String: Query String (e.g., id=123&name=test)
Frequently Asked Questions
Basics
What is a URL Query String?
A URL query string is the part of a URL that comes after the question mark (?). It contains key-value pairs separated by ampersands (&), used to pass data to web servers. For example, in 'https://example.com/search?q=hello&lang=en', the query string is 'q=hello&lang=en'.
What Are the Components of a URL?
A URL consists of several parts: Protocol (https://), Domain (example.com), Port (:8080), Path (/page), Query String (?key=value), and Fragment (#section). The query string allows passing parameters to the server, while the fragment is used for client-side navigation.
What's the Difference Between GET and POST Parameters?
GET parameters are visible in the URL query string and are suitable for bookmarkable, shareable links with non-sensitive data. POST parameters are sent in the request body, hidden from the URL, and used for sensitive data or large payloads. GET has URL length limits (~2048 chars), while POST has no practical limit.
Security
Why Do URL Parameters Need to Be Encoded?
URL encoding is necessary because URLs can only contain ASCII characters, and certain characters have special meanings (like &, =, ?, /). Characters like spaces, Chinese characters, or special symbols must be percent-encoded (e.g., space becomes %20) to be safely transmitted in URLs.
What Are Security Considerations for URL Parameters?
Never put sensitive data (passwords, tokens) in URL parameters as they appear in browser history, server logs, and referrer headers. Always validate and sanitize parameters on the server to prevent injection attacks. Use HTTPS to encrypt the entire URL including parameters during transmission.
Usage
How to Parse URL Parameters in JavaScript?
In JavaScript, you can use the URLSearchParams API:
const url = new URL('https://example.com?name=John&age=30');
const params = url.searchParams;
console.log(params.get('name')); // 'John'
console.log(params.get('age')); // '30'
// Or get all parameters
for (const [key, value] of params) {
console.log(key, value);
}How to Handle Multiple Values for the Same Parameter?
URLs can have multiple values for the same parameter (e.g., ?color=red&color=blue). Use URLSearchParams.getAll('color') to get all values as an array. Some servers use bracket notation like ?color[]=red&color[]=blue for array parameters.
What Are Hash Fragment Parameters?
Hash fragments (after #) are typically used for client-side navigation and single-page applications. Some frameworks pass parameters in the hash (e.g., #/page?id=123). Unlike query strings, hash fragments are never sent to the server - they're processed entirely by the browser.
Query Parameter Debugging Checklist
Repeated keys
Some APIs accept repeated keys like ?tag=js&tag=vue, while others expect comma-separated or bracket syntax. Check whether your server reads the first value, the last value, or all values.
Hash-only parameters
Values after # are not sent to the server. If analytics, OAuth redirects, or SPA routes seem missing on the backend, check whether the data is in the fragment instead of the query string.
Tracking noise
UTM, fbclid, gclid, and similar tracking parameters can hide the real business parameters. Remove or group them before debugging API behavior.
Sensitive values
Tokens, emails, and private IDs in query strings can leak through logs, browser history, and referrers. Move sensitive data to headers or request bodies when possible.