URL Codec

Freely convert between Text, URL Encoded, and Component Encoded formats

URL Codec is a free online tool for easy URL string encoding and decoding. Supports both URL encoding for form data transmission (application/x-www-form-urlencoded) and RFC 3986 compliant component encoding. Your input data is not stored on the server, so you can safely convert sensitive information.

How to Use

Using the URL Codec is very simple:

Step 1: Enter Data and Select Input Format
Enter the data you want to convert in the text box below. Select the input format (Text, URL Encoded, or Component Encoded).
Step 2: Select Output Format
Choose the conversion destination format. You can select from Text, URL Encoded (for forms), or Component Encoded (RFC 3986 compliant).
Step 3: Click Convert Button
Click the "Convert" button and the entered data will be instantly converted to the selected format. Copy the result and use it.

Your input data is not stored on the server. All processing is completed in the browser, and your privacy is completely protected.

URL Conversion Tool

Input Format

Output Format

Enter Data to Convert

Conversion Result

Practical Use Cases for URL Codec

URL Codec is used in the following situations in web development and API integration:

Form Data Encoding

Encode and decode data submitted from HTML forms (application/x-www-form-urlencoded). Ideal for checking and debugging POST/GET parameters. Spaces are converted to "+".

URL Query Parameter Generation

Encode search queries and filter conditions as URL query parameters. Convert search keywords containing Japanese or special characters to URL-safe format. Example: "Tokyo Tower" → "Tokyo%20Tower"

REST API Parameter Encoding

Encode parameters included in REST API endpoint URLs in RFC 3986 compliant format. Using component encoding, spaces are converted to "%20", and slashes and colons are also preserved.

URL Decoding and Debugging

Decode encoded URLs displayed in browser address bars or access logs to check the original string. Useful for identifying error causes and analyzing logs.

OAuth Authentication Parameter Processing

Encode and decode OAuth 2.0 redirect_uri and state parameters. Used for verification and debugging of URL parameters sent within authentication flows.

What is URL Encoding? Understanding Encoding Methods

URL encoding (percent encoding) is a method of representing characters that cannot be used in URLs or special characters using a combination of the "%" symbol and hexadecimal numbers. Since URLs originally handle only ASCII characters, it is necessary when sending multibyte characters like Japanese or special symbols.

Types of URL Encoding

Form Encoding (application/x-www-form-urlencoded): Method used in HTML forms. Converts spaces to "+" and other special characters to "%XX" format. Equivalent to PHP's urlencode().
Component Encoding (RFC 3986): Method used in each component of a URL (path, query parameter values, etc.). Converts spaces to "%20" and performs more strict encoding. Equivalent to PHP's rawurlencode().

Encoding Examples

Text "Hello World!" → Form Encoding "Hello+World%21"
Text "Hello World!" → Component Encoding "Hello%20World%21"
Japanese "こんにちは" → UTF-8 Encoding "%E3%81%93%E3%82%93%E3%81%AB%E3%81%A1%E3%81%AF"

Which Should You Use?

Use form encoding when submitting HTML forms, and component encoding for REST API URL paths and query parameters. If in doubt, choosing component encoding (RFC 3986) will work correctly in most cases.

Frequently Asked Questions (FAQ)

Are URL encoding and percent encoding the same?

Yes, they are the same. URL encoding is officially called "percent encoding" and is named so because it uses the "%" symbol to represent characters.

What is the difference between form encoding and component encoding?

The main difference is the handling of spaces. Form encoding (application/x-www-form-urlencoded) converts spaces to "+", while component encoding (RFC 3986) converts them to "%20". The character set to be encoded also differs slightly.

What happens when Japanese is URL encoded?

Multibyte characters like Japanese are converted to UTF-8 byte sequences, and then each byte is encoded in "%XX" format. For example, "あ" becomes "%E3%81%82" (3 bytes).

What characters are encoded?

Most characters other than alphanumeric characters (A-Z, a-z, 0-9), hyphens (-), underscores (_), periods (.), and tildes (~) are encoded. Spaces, slashes (/), colons (:), non-ASCII characters like Japanese, and special symbols are subject to encoding.

Why are some strings unable to be decoded?

Decode errors occur in cases of invalid encoding format (no two hexadecimal digits after %, invalid UTF-8 byte sequence, etc.). Also, strings that have been encoded multiple times may require multiple decoding operations.

Is URL encoding encryption?

No, URL encoding is simply string encoding (conversion), not encryption. Encoded strings can be easily decoded and cannot be used for security protection purposes.

How do I perform URL encoding in programming languages?

Each language has built-in functions. JavaScript: encodeURIComponent(), Python: urllib.parse.quote(), PHP: rawurlencode(), Java: URLEncoder.encode(), Ruby: ERB::Util.url_encode(), etc. are available.

What is double encoding?

It is re-encoding a string that has already been encoded. For example, re-encoding "%20" becomes "%2520". Unintentional double encoding can cause bugs, so caution is necessary.