URL Encoding Explained — Why %20 Means Space and How It Works

Why URLs Cannot Contain Every Character

A URL is text, but it is special text. The URL specification (RFC 3986) defines a strict set of characters that are allowed — letters, digits, and a handful of special characters like -, _, ., and ~. Characters outside this set must be encoded before they appear in a URL.

The reason is ambiguity. Some characters have special meaning in URL syntax. The ? separates the path from the query string. The & separates query parameters from each other. The = separates parameter names from values. The # starts a fragment identifier.

If your query parameter value contains a &, the URL parser would interpret it as the end of that parameter and the start of the next one. To include these characters literally, they must be encoded in a way that tells the parser "this is data, not structure."

How Percent Encoding Works

Percent encoding replaces each unsafe character with a % sign followed by the two-digit hexadecimal ASCII code for that character.

Space is ASCII 32. In hexadecimal, 32 is 20. So a space becomes %20. That is all. You can verify any character: look up its ASCII code, convert to hex, add a % in front.

A few common encodings worth knowing:

• Space → %20 (or + in form encoding)
• @ → %40
• : → %3A
• / → %2F
• ? → %3F
• = → %3D
• & → %26

Non-ASCII characters (accented letters, Chinese characters, emoji) are first converted to their UTF-8 byte sequences, and then each byte is percent-encoded. An emoji might become several %xx sequences in a URL.

The Two Types of URL Encoding

URL encoding (also called percent encoding) — encodes everything that is not in the allowed set of unreserved characters. Used for encoding entire URLs or URI components.

Form encoding — Used specifically for HTML form data submitted via GET or POST. Nearly identical to percent encoding but uses + instead of %20 for spaces. This is what browsers use when you submit a form.

You see both in the wild. An API endpoint might use %20 for spaces in its URL structure, while form submissions use +. Knowing the difference prevents subtle bugs when building or debugging APIs.

Practical Uses for URL Encoding

Building API requests — Any query parameter that might contain special characters needs to be URL-encoded before being appended to a URL. Most HTTP libraries do this automatically, but knowing what is happening helps when debugging raw requests.

Reading server logs — Log files show encoded URLs. Decoding them makes the actual paths and parameters readable.

Debugging redirects — Redirect chains often involve URL-encoded destination URLs nested inside other URL parameters. Decoding these step by step reveals the actual redirect target.

Our URL Encoder/Decoder tool handles both encoding and decoding instantly. Paste a URL or text string and get the encoded or decoded result immediately, no installation required.