URL Encoding in HTML: Special Characters in Links

A web address can only contain a limited set of characters. Everything else must be percent encoded: replaced by a % followed by two hex digits.

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<a href="search.html?q=cats%20and%20dogs">Search for cats and dogs</a>

Where it matters

• Links with query strings: the part after ? often contains user text.
• File names: a file called my photo.jpg should be linked as my%20photo.jpg. It is easier to avoid spaces in file names altogether.
• mailto links with a subject, as in Email links.

Forms do it for you

When a form with method="get" is sent, the browser encodes the values automatically.

In JavaScript

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encodeURIComponent("cats & dogs");  // "cats%20%26%20dogs"

Use encodeURIComponent when you build a link from user text.