What is URL encoding?

URL encoding (percent-encoding) replaces characters that are unsafe or ambiguous inside a URL with a % followed by two hexadecimal digits representing that character's byte value. For example, a space becomes %20 and an ampersand becomes %26.

What is the difference between encodeURI and encodeURIComponent?

encodeURI encodes a complete URL and deliberately leaves structural characters like / ? # : untouched since they define the URL's structure. encodeURIComponent encodes everything except letters, digits, and - _ . ~, including those structural characters — it is the correct function for encoding a single value that will be placed inside a URL, such as one query parameter.

When do I need URL encoding?

Any time you're inserting user-generated or arbitrary text into a query string, path segment, or form submission — for example, encoding a search term that might contain spaces or an & character before appending it to a URL as ?q=value.

What is the difference between percent-encoding and HTML entity encoding?

Percent-encoding (%20, %26) makes a value safe for use inside a URL's structure. HTML entity encoding (&, <) makes a value safe for use inside HTML markup, preventing it from being misread as a tag. They solve different problems and are frequently confused, which causes double-encoding bugs when both are applied to the same value incorrectly.

Why does decoding sometimes throw an error?

decodeURIComponent throws a URIError when it encounters a malformed percent sequence — a % not followed by two valid hexadecimal digits, or a partial multi-byte UTF-8 sequence that doesn't form a complete valid character. This usually means the input wasn't actually valid percent-encoded text, or was truncated when copied.

Does this tool encode entire URLs or just parts of them?

It encodes and decodes using encodeURIComponent/decodeURIComponent, which is designed for individual values like a single query parameter — running a full URL (with its scheme and slashes) through it will also encode the // and : that are supposed to remain untouched, breaking the URL structure.

How are non-ASCII characters like emoji or accented letters handled?

They are first converted to their UTF-8 byte representation, and each byte is then percent-encoded separately — which is why a single emoji or accented character can expand into several %XX sequences rather than just one.

Is + the same as %20 for encoding a space?

Not quite — they come from different contexts. %20 is the standard percent-encoding for a space anywhere in a URI. + specifically means a space only within the application/x-www-form-urlencoded format used for HTML form submissions and classic query strings, and a literal + in other contexts must itself be encoded as %2B to avoid ambiguity.

Can this tool help debug a broken redirect or webhook URL?

Yes — pasting a URL containing an unexpectedly truncated or garbled query string parameter and decoding it will often reveal that a nested URL or special character wasn't encoded before being embedded, which is one of the most common causes of broken redirect and callback URLs.

Is my data sent to a server when I encode or decode it?

No. Both operations run entirely with the browser's native encodeURIComponent and decodeURIComponent functions — nothing you enter is ever transmitted anywhere, which is useful when working with sensitive tokens or internal URLs.

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What is Encode / Decode URL?

Encode/Decode URL is a free online tool that percent-encodes special characters for safe use in URLs or decodes percent-encoded strings back to readable text. Essential for web developers working with query strings, API parameters, or URIs — this tool specifically implements encodeURIComponent()/decodeURIComponent() behavior, which is the correct choice for encoding individual values rather than whole URLs.

A URL can only reliably contain a limited set of characters — letters, digits, and a handful of punctuation marks defined by the URI specification (RFC 3986). Everything else — spaces, ampersands, question marks appearing inside a value, non-ASCII letters, emoji — has to be represented using percent-encoding: a % followed by two hexadecimal digits representing that character's byte value. A space becomes %20, an ampersand becomes %26, and an accented character like é becomes %C3%A9 once it's broken into its UTF-8 byte representation. Skip this step and the browser, server, or intermediate proxy is left guessing where one URL component ends and another begins — a bare & inside a query parameter value looks identical to the separator between two different parameters, which is exactly the class of bug this tool exists to prevent.

JavaScript actually provides two related but distinctly different encoding functions, and picking the wrong one is a common source of broken links. encodeURI() is meant for encoding an entire URL and deliberately leaves structural characters like /, ?, #, and : untouched, since those are meaningful delimiters in a full URL and shouldn't be escaped. encodeURIComponent() — what this tool uses — is meant for encoding a single component, such as one query parameter's value, and encodes everything except unreserved characters (letters, digits, and - _ . ~), including characters like &, =, and / that would otherwise be misread as URL structure if they appeared inside a value.

A related and equally important distinction is between percent-encoding, which this tool implements, and HTML entity encoding (turning & into &), which is a completely separate escaping mechanism used to prevent characters from being misinterpreted as HTML markup rather than URL structure. Confusing the two is a frequent source of double-encoding bugs, where a value gets percent-encoded and then HTML-entity-encoded (or vice versa) and comes out wrong on the other end.

Everything runs using the browser's native, spec-compliant encodeURIComponent() and decodeURIComponent() functions — no custom regex substitution that could miss an edge case — and no text you enter is ever sent to a server.

Building or debugging a sitemap URL? Generate Sitemap produces properly-formed URLs directly.

How It Works

Encoding passes your input directly to JavaScript's built-in encodeURIComponent(), which converts every character outside its small unreserved set (A-Z, a-z, 0-9, and - _ . ~) into UTF-8 bytes and represents each byte as a %XX hexadecimal escape — so a single non-ASCII character can expand into two or three percent-encoded triplets depending on how many UTF-8 bytes it requires. Decoding passes a percent-encoded string to decodeURIComponent(), which reverses the exact same mapping, reconstructing the original UTF-8 byte sequence from each %XX triplet and decoding it back to readable text. If the input to decode contains a malformed sequence — a stray % not followed by two valid hex digits, or a truncated multi-byte UTF-8 sequence — decodeURIComponent() throws a URIError, which this tool catches and reports as a specific, readable error rather than returning corrupted or partial output.

How to Use

Paste your URL or string

Enter the URL or text string you need to encode or decode in the input field.

Encode or decode

Click "Encode URL" to percent-encode special characters, or "Decode URL" to convert encoded sequences back to readable text.

Copy the result

Copy the output for use in web development, API calls, or browser address bars.

Who Uses This Tool

🔗

Query String Parameters

Encode user-supplied search terms or filter values before appending them as URL query parameters.

🛠️

API Request Construction

Percent-encode parameter values when building API request URLs programmatically to prevent injection issues.

🌍

Internationalized URLs

Encode non-ASCII characters like accented letters or CJK characters so they are safe to use in URLs.

🔍

Debugging Encoded URLs

Decode obfuscated or percent-encoded URLs from logs or redirects to read the original destination.

📧

Mailto Link Parameters

Encode subject and body text for mailto: links to ensure special characters render correctly in email clients.

📦

Redirect URL Encoding

Encode return_url or redirect parameters that contain slashes and question marks to keep the parent URL valid.

Why Choose This Tool

encodeURIComponent Accuracy

Uses JavaScript's encodeURIComponent which encodes all unsafe characters correctly for query parameter values.

Decode Mode Included

Decode any percent-encoded string back to readable text with a single button, covering both encode and decode workflows.

Malformed Sequence Detection

Shows a clear error when decoding an invalid percent-encoded sequence rather than returning corrupted output.

Unicode Handling

Correctly encodes multi-byte Unicode characters to their full percent-encoded form per the URI specification.

Instant Results

Encoding and decoding run synchronously in the browser so output appears immediately without any delay.

No Upload Required

All processing is client-side so you can safely encode sensitive query parameters and tokens offline.

Key Benefits

Encodes all special characters for safe use inside a URL query parameter

Decodes percent-encoded strings back to readable text

Uses encodeURIComponent/decodeURIComponent — correct for individual values, not whole URLs

Handles multi-byte Unicode characters correctly via UTF-8 percent-encoding

Shows a specific error for malformed percent-encoded sequences instead of silent corruption

One-click copy output button

Frequently Asked Questions

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Encode / Decode URL