URL Encoder & Decoder - Free Online Percent-Encoding Tool

Query String Parameters

When building URLs with user-provided values as query parameters, always URL-encode the values. A search query like "C++ programming" must be encoded to C%2B%2B%20programming to prevent the + and spaces from being misinterpreted as URL syntax. Failing to encode allows users to inject arbitrary URL components (URL injection attacks).

REST API Requests

When passing data as URL parameters in REST API calls, all parameter values must be URL-encoded. This is especially important for filter values, search terms, email addresses, file paths, and any user-generated content embedded in API URLs. Use URLSearchParams in JavaScript to build query strings automatically.

Redirect URLs

When implementing login redirects, OAuth callbacks, or post-action redirects where a URL is passed as a parameter, the return URL must be URL-encoded. For example: /login?redirect=https%3A%2F%2Fapp.example.com%2Fdashboard. Without encoding, the nested URL would break the outer URL's structure.

Internationalized URLs (IDN)

URLs can contain Unicode characters (international domain names, non-Latin path segments) which must be percent-encoded for use in HTTP requests. For example, Chinese, Arabic, or emoji characters in URLs are encoded as UTF-8 byte sequences: the path /café becomes /caf%C3%A9. Browsers display the decoded "pretty" form while sending the encoded form in HTTP headers.

Form Data Submission

HTML form submission with method="GET" URL-encodes all form field values and appends them as query parameters. The application/x-www-form-urlencoded content type (also used for POST form data) requires all values to be URL-encoded with + representing spaces instead of %20.

Email Links (mailto:)

The mailto: URI scheme uses URL encoding for subject, body, and recipient parameters. For example: mailto:[email protected]?subject=Hello%20World&body=Check%20this%20out%3A%20https%3A%2F%2Fexample.com. Special characters in the subject and body must be encoded to prevent parsing errors.

JavaScript

// Encode a parameter value
const encoded = encodeURIComponent("Hello World & more!");
// "Hello%20World%20%26%20more!"

// Decode
const decoded = decodeURIComponent("Hello%20World");
// "Hello World"

// Build a full query string safely
const params = new URLSearchParams({
  q: "C++ programming",
  lang: "en"
});
const url = `/search?${params}`;

Python

from urllib.parse import quote, unquote, urlencode

# Encode
encoded = quote("Hello World & more!")
# "Hello%20World%20%26%20more%21"

# Decode
decoded = unquote("Hello%20World")
# "Hello World"

# Build query string
params = {"q": "C++ programming", "lang": "en"}
query = urlencode(params)
# q=C%2B%2B+programming&lang=en

PHP

// Encode
$encoded = urlencode("Hello World & more!");
// "Hello+World+%26+more%21"

// rawurlencode follows RFC 3986
$encoded = rawurlencode("Hello World");
// "Hello%20World"

// Decode
$decoded = urldecode("Hello+World");
// "Hello World"

Node.js

const { URLSearchParams } = require("url");

// Encode value
const encoded = encodeURIComponent("Hello World");

// Build query string
const params = new URLSearchParams({
  search: "hello world",
  filter: "type:image"
});
console.log(params.toString());
// search=hello+world&filter=type%3Aimage