# How to encode or decode a URL in Node.js

By Atta Ur Rehman Shah (https://attacomsian.com/about). Published Jun 27, 2021, updated Oct 3, 2022. Topics: Node.js.
Canonical URL: https://attacomsian.com/blog/nodejs-encode-decode-url

> Learn how to use Node.js built-in modules and JavaScript functions to encode or decode a URL string in a Node.js application.

URL encoding is commonly used to avoid cross-site scripting (XSS) attacks by encoding special characters in a URL. It converts a string into a valid URL format making the transmitted data more reliable and secure.

In this article, you'll learn how to encode or decode a URL string and query string parameters in a Node.js application.

## URL Encoding

Since Node.js is a JavaScript runtime built on Chrome's V8 JavaScript engine, you can use JavaScript methods such as `encodeURI()` and `encodeURIComponent()` to [encode a URL](https://attacomsian.com/blog/javascript-encode-url).

### `encodeURI` Method

The `encodeURI()` method encodes a complete URL, including encodes special characters except `~!$&@#*()=:/,;?+` characters:

```javascript
const url = 'http://example.com/!Learn Node$/ Example'

// Encode complete URL
const encodedUrl = encodeURI(url)

// Print encoded URL
console.log(encodedUrl)

// http://example.com/!Learn%20Node$/%20Example
```

### `encodeURIComponent()` Method

You should use the `encodeURIComponent()` method to encode special characters in URI components. This method is suitable for encoding URL components such as query string parameters and not the complete URL. 

Here is an example:

```javascript
const baseUrl = 'http://example.com/search?q='
const query = 'SELECT * from users WHERE id = 1'

// Encode query string
const encodedQuery = encodeURIComponent(query)

// Build full URL
const url = baseUrl + encodedQuery

// Print full URL
console.log(url)

// http://example.com/search?q=SELECT%20*%20from%20users%20WHERE%20id%20%3D%201
```

### `querystring` Module

You could also use the Node.js built-in `querystring` module to encode a URL. This module provides utility methods for parsing and formatting URL query strings:

```javascript
const querystring = require('querystring')

const baseUrl = 'http://example.com/search?'
const query = 'SELECT * from users WHERE id = 1'

// Encode query string
const encodedQuery = querystring.stringify({ q: query })

// Build full URL
const url = baseUrl + encodedQuery

// Print full URL
console.log(url)

// http://example.com/search?q=SELECT%20*%20from%20users%20WHERE%20id%20%3D%201
```

## URL Decoding

URL decoding is the opposite of the encoding process. It converts the encoded URL strings and query parameters back to their regular formats.

JavaScript provides `decodeURI()` and `decodeURIComponent()` that can also be used in Node.js to perform URL decoding.

### `decodeURI` Method

The `decodeURI()` method is used to decode a complete URL:

```javascript
const encodedUrl = 'http://example.com/!Learn%20Node$/%20Example'

// Decode URL
const url = decodeURI(encodedUrl)

// Print URL
console.log(url)

// http://example.com/!Learn Node$/ Example
```

### `decodeURIComponent()` Method

The `decodeURIComponent()` function is used to decode URL components:

```javascript
const query = 'Dankeschön für Ihre €100'

// perofrm encode/decode
const encodedStr = encodeURIComponent(query)
const decodedStr = decodeURIComponent(encodedStr)

// print values
console.log(`Encoded Query: ${encodedStr}`)
console.log(`Decoded Query: ${decodedStr}`)

// Output
// Encoded Query: Dankesch%C3%B6n%20f%C3%BCr%20Ihre%20%E2%82%AC100
// Decoded Query: Dankeschön für Ihre €100
```