Is my URL or string data sent to external servers?

No. All percent-encoding, decoding, and query string parsing operations execute locally in your web browser session using client-side JavaScript.

What causes a URIError: malformed URI sequence during decoding?

This error occurs when the input contains an invalid percent sequence (such as a standalone % not followed by two valid hexadecimal digits) or an incomplete UTF-8 multi-byte sequence.

URL Encoder & Decoder with Query String Inspector

Q: What is the difference between encodeURI and encodeURIComponent?

encodeURI is designed for complete URLs; it leaves protocol and routing delimiters (: / ? # & =) unencoded. encodeURIComponent is designed for isolated query parameter keys and values; it encodes all reserved characters to prevent URL structural corruption.

Q: When should spaces be encoded as %20 versus +?

%20 is the official percent-encoding standard defined in RFC 3986 for path segments and URIs. The plus symbol (+) is specifically used in application/x-www-form-urlencoded query strings and classic HTML form submissions.

Sample Inputs:

Input String 0 Characters

Output Result 0 Characters

Scope:

Spaces:

Real-time Encode

Client-Side Execution

🔍 Parsed URL Components & Parameters

Base Origin & Path: -

Anchor Fragment: -

Parameter Key	Decoded Parameter Value

1. The Mechanics of URL Percent-Encoding

Uniform Resource Identifiers (URIs) across HTTP/HTTPS networks must conform strictly to the US-ASCII character set. Because URLs use specific punctuation characters like ?, &, =, and / to define protocol hierarchy, path segments, and query parameters, arbitrary strings cannot contain these literal symbols without ambiguity.

Percent-encoding maps reserved, unprintable, or non-ASCII multibyte characters (like UTF-8 international text or emojis) into a % followed by a two-digit hexadecimal byte value. For instance, the UTF-8 symbol & becomes %26, preventing downstream web servers and reverse proxies from truncating parameter pairs.

2. URL Character Classifications (RFC 3986)

Classification	Characters Included	Encoding Policy
Unreserved	`A-Z`, `a-z`, `0-9`, `-`, `_`, `.`, `~`	Never encoded; safe in all URL contexts
Reserved (General)	`:`, `/`, `?`, `#`, `[`, `]`, `@`	Encoded inside query values; preserved in full URIs
Reserved (Sub-delimiters)	`!`, `$`, `&`, `'`, `(`, `)`, `*`, `+`, `,`, `;`, `=`	Encoded when separating keys/values
Non-ASCII (Multibyte)	Accented letters, non-Latin scripts, Emojis	Converted to UTF-8 byte sequences, then percent-encoded

3. Technical Limitations & Error Prevention

Incomplete UTF-8 Sequences: Truncated hex sequences like %E0%A4 will trigger a URIError during decoding because JavaScript expects complete multi-byte representations.
Contextual Scope Matters: Do not encode entire URLs using encodeURIComponent or the protocol delimiter (https://) will become https%3A%2F%2F, breaking client routing. Use Full URI mode for full links and Component mode for parameters.
Hash Fragment Scope: Anchor fragments (prefixed with #) are processed on the client side and are never transmitted to the web server in standard HTTP GET request headers.

4. Execution Architecture & Privacy Transparency

All percent-encoding, decoding, string replacements, and query parsing routines are processed directly in-memory within your web browser session using client-side JavaScript. No URL strings, credentials, or query parameters are ever uploaded to remote servers or stored in databases.

Standard analytics (Google Analytics) and advertising scripts (Google AdSense) operate on this website for operational analytics and ad delivery in accordance with our Privacy Policy.

5. Explore Related Developer Utilities

6. Frequently Asked Questions

What is the difference between encodeURI and encodeURIComponent?

encodeURI is meant for full URLs and preserves protocol and path delimiters like : / ? # & =. encodeURIComponent encodes all reserved characters, making it suitable for single query string keys and values.

When should spaces be encoded as %20 versus +?

%20 is the standard percent-encoding defined in RFC 3986 for URIs. The plus symbol (+) is specific to HTML form data submissions (application/x-www-form-urlencoded).

Is my URL data stored on any server?

No. All calculations run locally in your browser sandbox using JavaScript. No input data is logged on remote servers.

What causes a URIError: malformed URI sequence?

This error happens when the input contains an invalid percent sequence (such as % without two hex digits) or an incomplete multi-byte UTF-8 character.