infoOverview

A URL full of %XX sequences is unreadable at a glance, and remembering whether encodeURI or encodeURIComponent is the right call for a given string trips up most developers at some point. This tool runs both directions — encode a raw string into percent-encoded form, or decode an encoded one back to plain text — using the exact same JavaScript methods you'd call in code, so the result matches what your app will actually produce.

checklistHow to Use

1. 1Type or paste the text into String to convert — this works whether it's already encoded or still plain text.
2. 2Set Mode to Encode or Decode depending on which direction you need.
3. 3Turning on Convert all URL symbols (e.g. / and ?) as well switches to encodeURIComponent behavior, encoding every reserved character. Leave it off to use encodeURI behavior, which leaves URL structure characters like / and ? untouched.
4. 4Click Convert to see the result, or Clear to start over.

menu_bookSpecifications & Glossary

• encodeURI: Does not encode characters that are valid in a URL (scheme http://, path separator /, query characters ?, =, &, etc.). Use when passing the entire URL.
• encodeURIComponent: Encodes all characters except A-Z a-z 0-9 - _ . ! ~ * ' ( ). Use when passing a part of a URL, such as a query parameter value.
• Percent encoding (RFC 3986): The mechanism behind the %XX notation. Each character is first encoded as UTF-8 bytes, then each byte is written as %XX in hex — a multi-byte character like "あ" expands to multiple %XX groups, e.g. %E3%81%82.
• Decoding: Supports decodeURI and decodeURIComponent to restore encoded strings back to their original text.
• Difference between encodeURI and encodeURIComponent: encodeURI does not encode URL structural characters such as :, /, ?, and #, while encodeURIComponent encodes all of them.
• Double encoding: Encoding a string that's already encoded turns the % character itself into %25, breaking a clean round trip back to the original text. Check whether the input already contains %XX sequences before converting.

lightbulbUse Cases

• Encoding non-ASCII text or special characters before putting them into an API request's query parameters.
• Converting form field values into a URL-safe format before building a query string by hand.
• Making sense of a long percent-encoded URL from a browser address bar, server log, or bug report.
• Settling the classic "+ vs %20" confusion: form submissions (application/x-www-form-urlencoded) traditionally encode a space as +, while encodeURIComponent and a URL's path always use %20 — mixing the two conventions is a common source of subtly broken query strings.
• Converting a URL with a Japanese domain or path into a form that's safe to share or paste elsewhere.

quizFAQ

Should I use encodeURIComponent or encodeURI?

Use encodeURIComponent when you're encoding a fragment of a URL — a query parameter value, a single path segment. Use encodeURI when you already have a complete, well-formed URL and want to encode it as a whole while keeping structural characters like / and ? intact.

How does encoding handle URLs containing Japanese text?

Japanese and other multi-byte characters are first converted to their UTF-8 byte sequence, and each byte is then written as %XX. The character "あ" is 3 bytes in UTF-8, so it expands into the three-part sequence %E3%81%82.

What happens if I accidentally encode a string twice?

Encoding an already-encoded string a second time turns the literal % character into %25, and decoding it once no longer gets you back to the original string. Check whether your input is already encoded before running it through the tool again.

Which characters in a query parameter actually need encoding?

Spaces and multi-byte characters like Japanese are obvious candidates, but reserved characters that carry structural meaning — &, =, ?, and # — need encoding too if a value might contain them. Enabling Convert all URL symbols as well encodes all of these along with everything else.

Does this tool encode spaces as "+" or as "%20"?

This tool follows JavaScript's built-in encodeURI/encodeURIComponent behavior, which always represents a space as %20. The "+" convention for spaces belongs to application/x-www-form-urlencoded form submissions, a separate encoding scheme that this tool doesn't produce.

In what situations does decoding fail?

Decoding fails when a "%" isn't followed by exactly two hex digits (for example, a string that ends abruptly with "%2"), or when the decoded bytes don't form valid UTF-8. Double-check the string before it was encoded and try again.