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Encode text for safe use in URLs or decode percent-encoded URL strings with our comprehensive URL Encoder Decoder. URL encoding converts special characters to their percent-encoded equivalents (like spaces to %20), ensuring URLs work correctly across all systems and browsers. This tool handles both standard URL encoding and form data encoding, crucial for developers building web applications, APIs, and tools that manipulate URLs. Whether you need to safely include query parameters with special characters, debug URL-encoded form submissions, work with international domain names using Punycode conversion, or decode URLs from logs and headers, this tool provides instant, reliable conversion. The tool supports both full URI encoding (preserving slashes and colons for proper URL structure) and component encoding (encoding everything for safe parameter values), giving you precise control over the encoding process.
Safely encode values for URL query parameters, ensuring special characters like & = ? # are properly escaped and don't break the URL structure.
Decode captured URL-encoded form data from logs and headers to inspect exact user input, making it easier to debug form submission issues and data validation problems.
Encode URLs containing non-ASCII characters, spaces, or symbols to ensure they work correctly when shared via email, chat, or embedded in documents.
Decode percent-encoded URLs returned by APIs to extract the actual destination and understand API response structure for integration.
Verify how your application handles encoded and decoded URL parameters by encoding test data and examining application behavior with various inputs.
Convert between full URI encoding and component encoding depending on whether you're building complete URLs or individual parameter values for API requests.
URL encoding, formally known as percent-encoding, is a mechanism defined in RFC 3986 for representing characters in a Uniform Resource Identifier (URI) that would otherwise be illegal, ambiguous, or problematic. The concept originates from the earliest days of the World Wide Web, when Tim Berners-Lee and his colleagues needed a way to ensure that URLs—the addresses that identify every resource on the internet—could be transmitted reliably across systems with different character set support and through protocols that imposed strict constraints on allowed characters.
The URL specification reserves certain characters for structural purposes. The question mark (?) separates the path from the query string, the ampersand (&) delimits query parameters, the hash (#) marks fragment identifiers, and the forward slash (/) delineates path segments. When data values contain these characters, they must be encoded to prevent the parser from misinterpreting them as structural delimiters. Percent-encoding achieves this by replacing each problematic character with a percent sign (%) followed by two hexadecimal digits representing the character's byte value. A space becomes %20, an ampersand becomes %26, and a plus sign becomes %2B.
The situation becomes more nuanced with Unicode text. Modern URLs frequently contain characters from non-Latin scripts—Chinese, Arabic, Cyrillic, and many others. The encoding process first converts the Unicode text to its UTF-8 byte representation, then percent-encodes each byte individually. A single Chinese character might expand into nine characters of percent-encoded output (three UTF-8 bytes, each encoded as three characters). This is why international URLs can become extremely long in their encoded form, even though browsers display them in their readable Unicode form.
Two distinct encoding functions exist in JavaScript and most programming environments, each serving a different purpose. The encodeURI function encodes a complete URI, preserving characters that are valid in URL structure such as colons, slashes, and question marks. The encodeURIComponent function encodes individual URI components like query parameter values, encoding everything except unreserved characters (letters, digits, hyphens, underscores, periods, and tildes). Choosing the wrong function is a common source of bugs: using encodeURIComponent on an entire URL will break its structure by encoding the slashes and colons, while using encodeURI on a parameter value will leave structural characters unescaped, potentially creating malformed URLs.
A historical curiosity is the treatment of spaces. Standard percent-encoding converts spaces to %20, but the application/x-www-form-urlencoded format used by HTML forms encodes spaces as plus signs (+). This dual representation persists today and occasionally causes confusion when systems disagree on which convention to use. Understanding these subtleties is essential for anyone building or debugging web applications that handle user input in URLs.
encodeURI encodes a full URI but preserves characters like :, /, and ? that are valid in URLs. encodeURIComponent encodes everything except letters, digits, and a few special characters, making it ideal for encoding individual query parameter values.
Spaces are not allowed in URLs. In standard percent-encoding, spaces become %20. In form data (application/x-www-form-urlencoded), spaces are encoded as +. Both represent a space but are used in different contexts.
Yes. Non-ASCII characters like accented letters, Chinese, or Arabic text are first encoded as UTF-8 bytes, then each byte is percent-encoded (e.g., %C3%A9 for e).
Always encode values placed in URL query parameters, path segments, or form submissions. This prevents special characters like &, =, and # from being misinterpreted as URL delimiters.
All processing happens directly in your browser. Your files never leave your device and are never uploaded to any server.