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URL Encode / Decode

Percent-encode query values or whole URLs, or decode them back to plain text.

Direction
0 characters
Encode as

Why URLs need percent-encoding

A URL can only safely contain a limited set of characters — letters, digits, and a handful of punctuation marks that have no special meaning in that position. Everything else (spaces, ampersands inside a value, non-English characters, slashes inside a value rather than as a path separator) has to be percent-encoded: replaced with % followed by its byte value in hex. A space becomes %20, an ampersand becomes %26, and so on.

Get this wrong and a URL either breaks outright or, worse, silently does the wrong thing — an unencoded &inside a query value looks like the start of the next parameter, quietly truncating or corrupting the one before it.

Example

Encoding hello world & more/less? as a single value gives:

hello%20world%20%26%20more%2Fless%3F

Every character outside letters, digits and -_.~ is escaped, including the slash and question mark, since as a value they carry no special meaning.

Component vs. full-URL encoding

The common mistake is running an entire URL through component-style encoding, which escapes the very characters (:, /, ?, &, =) that make it a URL in the first place. The rule of thumb: encode a value that will be placed inside a URL with the component option; only use the full-URL option on something that is already a complete, structurally valid URL and only needs its non-ASCII or space characters escaped.

Doing it in code

JavaScript

encodeURIComponent("hello world & more");  // "hello%20world%20%26%20more"
encodeURI("https://x.y/p q?a=b c");        // "https://x.y/p%20q?a=b%20c"
decodeURIComponent("hello%20world");       // "hello world"

Python

from urllib.parse import quote, unquote, quote_plus
quote("hello world & more")   # 'hello%20world%20%26%20more'
quote_plus("hello world")     # 'hello+world'
unquote("hello%20world")      # 'hello world'

URL Encode / Decode FAQ

What is the difference between the three encode options?

A single value (encodeURIComponent) escapes everything that isn’t a letter, digit or a small set of safe symbols — use it for one query parameter's value. A whole URL (encodeURI) leaves characters like : / ? # & = alone since they are structural, not data — use it when you have a complete URL you don’t want to break. Form field encoding is the same as a single value but turns spaces into "+", matching how HTML forms submit data.

Why would encoding the same text two different ways give different results for spaces?

A space becomes %20 under encodeURIComponent/encodeURI, but becomes + under the form-field convention (application/x-www-form-urlencoded), which is what browsers use for classic HTML form submissions.

When does decoding fail?

Percent-encoding is only valid when a "%" is followed by exactly two hexadecimal digits. Text that was cut off mid-sequence, or that contains a literal "%" that was never meant to be encoded, will fail to decode — the tool reports this rather than guessing.