URL Encode Decode Online

URL Encoding and Best Practices

This URL encode decode online tool applies percent-encoding to query strings and path segments per RFC 3986. URL encoding (also known as percent encoding) uses % followed by two hexadecimal digits. See Percent Encoding.

Unreserved Characters and Encoding Rules

Unreserved characters: ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_.~. Other characters should be converted to UTF-8 first and then percent-encoded byte by byte.

Encoding rules: 1. Unreserved characters remain unchanged 2. Other characters are first converted to UTF-8 3. Each byte of UTF-8 encoding is converted to percent encoding.

Related Tools

• Unicode To UTF-8
• HTML Entity Encoding
• Base64 Encoding

Best Practices

1. Always encode user input
2. Use the correct encoding function (e.g. encodeURIComponent vs encodeURI in JavaScript)
3. Pay attention to encoding scope
4. Avoid double encoding
5. Consider internationalization
6. Test edge cases
7. Follow RFC 3986

Encoding & Decoding

Paste the text or URL you want to process into the input field, then choose Encode or Decode:

• Encode — Converts special characters into %XX percent-encoded form so they can be safely included in a URL
• Decode — Restores %XX sequences back to their original readable characters

Results update in real time as you type.

encodeURI vs. encodeURIComponent

These two JavaScript functions are easy to confuse:

• encodeURI — Encodes a complete URL. It preserves structural characters like :, /, ?, #, &, and =
• encodeURIComponent — Encodes a single URL component (typically a query parameter value). It encodes nearly all special characters, including &, =, and /

Example:

Original URL: https://example.com/search?q=hello world&lang=en

encodeURI result:
https://example.com/search?q=hello%20world&lang=en
→ URL structure stays intact; only the space is encoded

encodeURIComponent result:
https%3A%2F%2Fexample.com%2Fsearch%3Fq%3Dhello%20world%26lang%3Den
→ Everything is encoded, breaking the URL structure

Rule of thumb: Use encodeURI for full URLs; use encodeURIComponent for individual query parameter values.

Handling Non-ASCII and Special Characters

Non-ASCII characters (such as Chinese, Arabic, or emoji) are first converted to their UTF-8 byte sequences and then percent-encoded byte by byte. For example, the character "ü" in UTF-8 is C3 BC, which becomes %C3%BC in a URL.

Common characters that need encoding:

Avoiding Double Encoding

Double encoding is one of the most common pitfalls. If a string has already been encoded once and you encode it again, the % characters themselves get encoded as %25:

Original:    hello world
First pass:  hello%20world        (correct)
Second pass: hello%2520world      (broken)

When decoding, if the result still contains %XX sequences, the original data was probably encoded multiple times—just decode again. In this tool, you can click Decode repeatedly until the output stops changing.

API

Note the different handling of reserved characters in various language APIs.

JavaScript

encodeURIComponent('山月')  // => '%E5%B1%B1%E6%9C%88'
decodeURIComponent('%E5%B1%B1%E6%9C%88')  // => '山月'
encodeURIComponent('(!')  // => '(!'

Python

from urllib.parse import quote, unquote
quote('山月')   # => '%E5%B1%B1%E6%9C%88'
unquote('%E5%B1%B1%E6%9C%88')  # => '山月'
quote('?!')   # => '%3F%21'

FAQ

Q: What's the difference between encodeURI and encodeURIComponent?

encodeURI is meant for encoding a complete URI—it leaves structurally significant characters like :, /, ?, #, &, and = untouched. encodeURIComponent is meant for encoding a single URI component (such as a query parameter value) and encodes nearly every special character. For example, applying encodeURI to https://example.com/search?q=hello world only encodes the space, while encodeURIComponent also encodes ://, /, ?, and =. Use encodeURIComponent when building query strings to avoid breaking the URL structure.

Q: Why do non-ASCII characters become %XX sequences in URLs?

The URL specification (RFC 3986) restricts URIs to a subset of ASCII characters. Characters outside that set—such as Chinese, accented letters, or emoji—must be percent-encoded before they can appear in a URL. The process converts each character to its UTF-8 byte representation and then writes each byte as % followed by two hexadecimal digits. For instance, the character "ñ" is C3 B1 in UTF-8, so it appears as %C3%B1 in a URL.

Q: What's the difference between URL encoding and Base64 encoding?

They serve different purposes. URL encoding (percent-encoding) makes special and non-ASCII characters safe for use within URLs—unaffected characters remain readable. Base64 encoding converts arbitrary binary data into a pure ASCII string and is commonly used to embed binary content in text-based formats like JSON, XML, or email. Base64 transforms all input, so the output is not human-readable. The two can be combined: for example, you might need to URL-encode a Base64 string when placing it in a query parameter.

Q: What is double encoding, and how do I avoid it?

Double encoding occurs when an already-encoded string is encoded again, turning each % into %25. For example, hello world encodes to hello%20world; encoding that a second time produces hello%2520world, which the server would decode back to the encoded form rather than the original text. This typically happens when multiple layers of a framework each apply encoding independently. To avoid it, designate a single point in your code that's responsible for encoding—usually right before the final URL is assembled—and don't encode at intermediate steps.

Q: Should spaces be encoded as %20 or +?

Both are used, but in different contexts. In URL paths and general URI components, spaces should be %20 per RFC 3986. In application/x-www-form-urlencoded data (the default format for HTML form submissions), spaces are represented as +—a historical convention. In JavaScript, encodeURIComponent produces %20, while URLSearchParams produces +. Most servers handle both correctly, but for consistency outside of form data, prefer %20.