NodejsHow-ToBeginner · 3 min read

How to Decode URL in Node.js: Simple Guide with Examples

In Node.js, you can decode a URL using the built-in decodeURIComponent() or decodeURI() functions. Use decodeURIComponent() to decode parts of a URL like query parameters, and decodeURI() to decode a full URL string.

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Syntax

decodeURIComponent(encodedURIComponent): Decodes a URL-encoded component, such as query parameters or path segments.

decodeURI(encodedURI): Decodes a full encoded URL but does not decode reserved characters like #, ?, or &.

javascript

decodeURIComponent(encodedURIComponent)
decodeURI(encodedURI)

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Example

This example shows how to decode an encoded URL component and a full encoded URL string using Node.js built-in functions.

javascript

const encodedComponent = 'Hello%20World%21';
const decodedComponent = decodeURIComponent(encodedComponent);

const encodedURL = 'https%3A%2F%2Fexample.com%2Fsearch%3Fq%3Dnode.js%2520url%2520decode';
const decodedURL = decodeURI(encodedURL);

console.log('Decoded Component:', decodedComponent);
console.log('Decoded URL:', decodedURL);

Output

Decoded Component: Hello World! Decoded URL: https://example.com/search?q=node.js%20url%20decode

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Common Pitfalls

1. Using decodeURI() on URL components: It won't decode characters like %26 (&) or %3F (?). Use decodeURIComponent() for parts like query parameters.

2. Double decoding: Decoding an already decoded string can cause errors or unexpected characters.

3. Passing invalid encoded strings: If the string is not properly encoded, decoding functions throw URIError. Always handle errors or validate input.

javascript

try {
  const badString = '%E0%A4%A'; // Invalid encoding
  console.log(decodeURIComponent(badString));
} catch (error) {
  console.error('Error decoding:', error.message);
}

// Correct usage
const goodString = '%E0%A4%A6';
console.log(decodeURIComponent(goodString));

Output

Error decoding: URI malformed द

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Quick Reference

Function	Use Case	Decodes Reserved Characters?
decodeURIComponent()	Decode URL parts like query parameters or path segments	Yes
decodeURI()	Decode full URL string without decoding reserved characters	No

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Key Takeaways

Use decodeURIComponent() to decode individual URL parts like query parameters.

Use decodeURI() to decode a full URL but reserved characters remain encoded.

Avoid double decoding to prevent errors or corrupted strings.

Always handle errors when decoding to catch malformed input.

Node.js built-in functions make URL decoding simple and reliable.