Free URL Encoder & Decoder

RFC 3986 Standard

RFC 3986 defines the Uniform Resource Identifier (URI) syntax and specifies percent-encoding rules. This standard ensures consistent URL encoding across all web technologies and platforms. The standard categorizes characters as unreserved (don't need encoding), reserved (must be encoded when used as data), and percent-encoded characters (already encoded).

Our URL Encoder follows RFC 3986 specifications precisely, ensuring compatibility with all web browsers, servers, and applications. The encoding process converts characters to their UTF-8 byte representation, then percent-encodes each byte that isn't an unreserved character. This approach handles international characters correctly and ensures maximum compatibility.

encodeURIComponent vs. encodeURI

JavaScript provides two encoding functions with different behaviors. encodeURIComponent encodes almost everything, including reserved characters like /, ?, and #, making it ideal for encoding individual URL components like query parameter values. encodeURI only encodes characters that are not part of the URI syntax, preserving the URL structure while encoding unsafe characters.

When encoding complete URLs, use encodeURI to preserve the URL structure. When encoding individual components (like query parameter values or path segments), use encodeURIComponent. Our tool automatically applies the appropriate encoding level, ensuring URLs are correctly formatted for their intended use case.

Understanding the difference prevents common encoding errors. For example, encoding a complete URL with encodeURIComponent will break it by encoding the / characters in the path, while encoding a query parameter value with encodeURI might not encode special characters that could break the URL structure.

Common Encoding Examples

Understanding common encoding examples helps developers work with URLs effectively. A space character encodes as %20 (or + in form data). The @ symbol encodes as %40, crucial for email addresses in URLs. Special characters like & encode as %26, important for preventing query parameter confusion.

International characters encode as multiple percent-encoded bytes. For example, the character é encodes as %C3%A9 in UTF-8 (two bytes). Emojis encode as multiple bytes—the smiley emoji 😀 encodes as %F0%9F%98%80. Our encoder handles all Unicode characters correctly, converting them to proper UTF-8 percent encoding.

Encoding is reversible—decoding converts percent-encoded sequences back to their original characters. However, decoding must be done carefully, as double-encoding (encoding already-encoded strings) creates incorrect URLs. Our decoder correctly handles standard percent-encoded strings and identifies double-encoded or malformed sequences.

When to Encode

Always encode user input before inserting it into URLs. Never trust user-provided data to be URL-safe—always encode query parameters, path segments, and other dynamic URL components. This prevents URL injection attacks and ensures reliable URL construction across different browsers and systems.

Encode filenames that will appear in URLs, especially when filenames contain spaces, special characters, or international characters. Even if your file system allows these characters, URLs have stricter requirements. Encode email addresses, phone numbers, and other data that might contain special characters.

When working with APIs, encode parameter values according to the API's specifications. Most REST APIs expect URL-encoded query parameters, while some may require different encoding schemes. Always check API documentation for encoding requirements and test encoding with sample data to ensure compatibility.

Avoiding Common Encoding Errors

Common encoding mistakes include double-encoding (encoding already-encoded strings), encoding complete URLs when only components need encoding, and forgetting to encode spaces in filenames or user input. Double-encoding creates URLs like %2520 instead of %20, breaking URL parsing.

Another common error is encoding only part of a URL component. For example, encoding just the spaces in "hello world" while leaving other characters unencoded can still cause issues if other special characters are present. Always encode complete values, not just individual characters.

Be careful with encoding in different contexts. URL components should use percent encoding, but HTML form data uses + for spaces (though modern forms typically use percent encoding). JavaScript template literals and string concatenation require explicit encoding, while some frameworks handle encoding automatically—always verify behavior for your specific use case.

Testing and Validation

Test encoded URLs across different browsers, as encoding behavior can vary slightly between implementations. Test with various special characters, international characters, and edge cases like empty strings, very long strings, and strings containing only special characters.

Validate that encoded URLs are correctly decoded by servers and applications. Test round-trip encoding and decoding to ensure data integrity. Use our encoder's decode function to verify that encoded URLs decode correctly, and test with real-world data from your application to catch encoding issues before they reach production.

Monitor URL encoding in production through error logs and analytics. Broken URLs often indicate encoding issues, and monitoring helps identify patterns. Use our tool for debugging URL encoding issues reported by users or discovered during testing, ensuring quick resolution of encoding problems.

RFC 3986 Standard

Read the official RFC specification that defines URI syntax and percent-encoding rules. This standard ensures consistent URL encoding across all web technologies and platforms, providing the foundation for reliable URL construction and parsing.

MDN Web Docs

Comprehensive documentation on URL encoding in web development, including JavaScript encodeURI and encodeURIComponent functions, browser APIs, and best practices for URL construction and manipulation.

Wikipedia Percent-encoding

Detailed information about percent-encoding history, technical details, character encoding tables, and usage examples across different web technologies and standards.