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Online URL Encoder & Decoder

By Daniel DeGroff

Online URL Encoder & Decoder

URL encoder and decoder

This tool can be used to encode or decode URL parameters. It won’t handle full URLs currently, but you can input parameters that are part of the query string and this will decode them. This is the same format that POST data from forms uses, so you can also capture that data and decode or encode it here as well.

Type or paste text or a URL into the text area above and the text will be Encoded as you type
Type or paste an encoded value into the text area above and the text will be Decoded as you type

What is URL encoding?

URL encoding, also known as percent encoding, is a crucial technique for ensuring the correct transmission of data over the internet. It involves converting characters, particularly those that are reserved, unprintable, or non-ASCII, into a format that can be transmitted over the web. URLs, for instance, can only contain ASCII alphanumeric characters and some safe characters like hyphen (-), underscore (_), tilde (~), and dot (.). Any other character must be encoded. URL encoding works by converting each character to one or more bytes, and each byte is then represented by two hexadecimal digits preceded by a percent sign (%). This is why it’s also referred to as percent encoding.

How do I encode a URL?

Our URL encoding and decoding tool allows you to input a standard URL, and then it will provide you with a UTF-8 encoded version, using ASCII characters.

The tool first converts each reserved, unprintable, or non-ASCII character to one or more bytes. Then each byte is represented by two hexadecimal digits preceded by a percent sign (%) - (e.g. %2E). That gives us the URL encoded value. The percent sign is used as an escape character. That’s why we also refer to URL encoding as percent encoding.

For instance, let’s look at how to URL encode the character @. To encode @, we first convert it into a sequence of bytes using its ASCII value. The ASCII value of @ in decimal is 64, which when converted to hexadecimal comes out to be 40. We then precede the hex value with percent sign, which gives us the final URL encoded value of %40.

What about URL decode?

URL decoding, also known as percent decoding, is essentially the reverse process of URL encoding. It involves converting the percent-encoded strings back into their original form.

How URL decoding works:

  1. The URL decoder scans the encoded string from left to right.
  2. If it encounters a regular character, it simply keeps it as it is.
  3. If it encounters a sequence starting with a percent sign (%), it treats the following two characters as hexadecimal digits. This sequence represents a single byte in the ASCII character set.
  • The URL decoder then converts this byte (expressed in hexadecimal format) back into the corresponding ASCII character.

Using our earlier example: the percent-encoded string %40 would be decoded to the @ character, because 40 is the hexadecimal representation of 64, which is the ASCII value for the @ character.

In terms of implementation, many programming languages offer built-in functions for URL decoding:

  • JavaScript: decodeURIComponent()
  • PHP: rawurldecode()
  • Python: urllib.parse.unquote()
  • Java: java.net.URLDecoder and java.net.URLEncoder

It’s important to use URL decoding when processing received data that may have been URL-encoded. This ensures that the data is correctly interpreted. However, it’s also crucial to consider potential security risks, as decoding URLs can potentially lead to injection attacks if not handled carefully. Always validate and sanitize your inputs, whether they are URL-encoded or not.

Why is it important to URL encode?

The importance of URL encoding is evident in various aspects of web development and internet communication. It is essential for preparing data for HTML form submission with content-type: application/x-www-form-urlencoded and is widely used within the Uniform Resource Identifier (URI) set, which includes both Uniform Resource Locator (URL) and Uniform Resource Name (URN).

The characters in a URL are either reserved or unreserved. Reserved characters have special meanings in certain contexts. For example, the forward slash (/) is used to separate different parts of a URL. When such a reserved character needs to be used for a different purpose, it must be percent-encoded. For instance, if / needs to be in a path segment, it must be represented as %2F or %2f instead.

However, not all reserved characters need to be encoded in all contexts. In the query part of a URI (the part after a ? character), for example, / is considered a reserved character but doesn’t usually need to be percent-encoded unless the specific URI scheme dictates otherwise. It’s also important to note that URLs that only differ by whether a reserved character is percent-encoded or appears literally are typically considered different unless it’s established that the reserved character in question has no reserved purpose.

URL encoding is vital for maintaining the integrity and readability of data transmitted over the internet. Without this process, URLs and other forms of web data could be misinterpreted or corrupted, leading to errors or security risks. Furthermore, URL encoding is implemented using various functions in programming languages, such as encodeURIComponent() in JavaScript, rawurlencode() in PHP, and Server.URLEncode() in ASP, emphasizing its widespread use in web development.