--- title: "Percent-encoding - Glossary | MDN" chunk: 1/3 source: "https://developer.mozilla.org/en-US/docs/Glossary/Percent-encoding" category: "reference" tags: "web, html, css, javascript, documentation" date_saved: "2026-05-05T05:40:13.513580+00:00" instance: "kb-cron" --- * [Skip to main content](https://developer.mozilla.org/en-US/docs/Glossary/Percent-encoding#content) * [Skip to search](https://developer.mozilla.org/en-US/docs/Glossary/Percent-encoding#search) [ MDN ](https://developer.mozilla.org/en-US/) HTML [HTML: Markup language](https://developer.mozilla.org/en-US/docs/Web/HTML) HTML reference * [Elements](https://developer.mozilla.org/en-US/docs/Web/HTML/Reference/Elements) * [Global attributes](https://developer.mozilla.org/en-US/docs/Web/HTML/Reference/Global_attributes) * [Attributes](https://developer.mozilla.org/en-US/docs/Web/HTML/Reference/Attributes) * [See all…](https://developer.mozilla.org/en-US/docs/Web/HTML/Reference "See all HTML references") HTML guides * 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[Glossary](https://developer.mozilla.org/en-US/docs/Glossary) 2. [Percent-encoding](https://developer.mozilla.org/en-US/docs/Glossary/Percent-encoding) # Percent-encoding **Percent-encoding** is a mechanism to encode 8-bit characters that have specific meaning in the context of [URLs](https://developer.mozilla.org/en-US/docs/Glossary/URL). It is sometimes called URL encoding. The encoding consists of a substitution: A '%' followed by the hexadecimal representation of the ASCII value of the replaced character. Special characters needing encoding are: `':'`, `'/'`, `'?'`, `'#'`, `'['`, `']'`, `'@'`, `'!'`, `'$'`, `'&'`, `"'"`, `'('`, `')'`, `'*'`, `'+'`, `','`, `';'`, `'='`, as well as `'%'` itself. Other characters don't need to be encoded, though they could. | Character | Encoding | | --- | --- | | `':'` | `%3A` | | `'/'` | `%2F` | | `'?'` | `%3F` | | `'#'` | `%23` | | `'['` | `%5B` | | `']'` | `%5D` | | `'@'` | `%40` | | `'!'` | `%21` | | `'$'` | `%24` | | `'&'` | `%26` | | `"'"` | `%27` | | `'('` | `%28` | | `')'` | `%29` | | `'*'` | `%2A` | | `'+'` | `%2B` | | `','` | `%2C` | | `';'` | `%3B` | | `'='` | `%3D` | | `'%'` | `%25` | | `' '` | `%20` or `+` | Depending on the context, the character `' '` is translated to a `'+'` (like in the percent-encoding version used in an `application/x-www-form-urlencoded` message), or in `'%20'` like on URLs. ## In this article * [See also](https://developer.mozilla.org/en-US/docs/Glossary/Percent-encoding#see_also) ## [See also](https://developer.mozilla.org/en-US/docs/Glossary/Percent-encoding#see_also) * Definition of [percent-encoding](https://en.wikipedia.org/wiki/Percent-encoding) in Wikipedia. * [RFC 3986](https://datatracker.ietf.org/doc/html/rfc3986), section 2.1, where this encoding is defined. * [`encodeURI()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/encodeURI) and [`encodeURIComponent()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/encodeURIComponent) — functions to percent-encode URLs