URL encoder / decoder

A query string that breaks without encoding

Say you want q=nails & tips as a search value. If you paste that raw into a URL, the & starts a new parameter and the space splits the request. Component mode turns the value into something a parser can treat as one field:

Build the URL as ?q= plus the encoded value, not by encoding the whole ?q=... string in component mode (that would encode the ? and = too).

Component vs full URL

Component matches encodeURIComponent / decodeURIComponent. Use it for one value you will drop into a query string, path segment, or header that expects a single token.

Full URL matches encodeURI / decodeURI. It escapes spaces and non-ASCII characters but leaves structural characters alone: :/?#[]@!$&'()*+,;=. Reach for it when the input is already shaped like https://example.com/path?x=1 and you only need the unsafe bits percent-encoded.

Wrong scope is a common bug: full-URL encode on a lonely a&b leaves the & untouched, which is usually not what you wanted for a query value.

Spaces, plus signs, and form bodies

This tool follows the JavaScript URL APIs: spaces become %20, and + stays +. HTML form encoding (application/x-www-form-urlencoded) historically used + for spaces. If you are talking to an API that still expects that dialect, encode with component mode, then replace %20 with + for that hop only. Decode the other way: turn + into a space before decodeURIComponent when the peer used form encoding.

What this page will not do

• Upload or log your string (no server round-trip).
• Parse or rebuild a full URL object graph. For query editing beyond encode/decode, use a dedicated URL builder.
• Base64 or JWT work. For payloads in Base64 see the Base64 encoder; for HS256 tokens see the JWT encoder.
• Guess which dialect a remote API wants. Check the docs for %20 vs + and for whether reserved characters should stay literal.

Percent-encode URLs in code

Encode one value, build a whole query string, and decode. Watch the space: path-style encoding gives %20, form encoding gives +.

JavaScript: encodeURIComponent and URLSearchParams

// One query value or path segment: encodeURIComponent
console.log(encodeURIComponent("a&b=c d/é")); // a%26b%3Dc%20d%2F%C3%A9

// Whole query strings: URLSearchParams (form encoding, space becomes +)
const qs = new URLSearchParams({ q: "rock & roll", page: "2" });
console.log(`https://example.com/search?${qs}`); // q=rock+%26+roll&page=2

console.log(decodeURIComponent("caf%C3%A9")); // café

Python: urllib.parse

from urllib.parse import quote, unquote, urlencode

print(quote("a&b=c d/é", safe=""))           # a%26b%3Dc%20d%2F%C3%A9
print(quote("/docs/my file.pdf"))           # keeps "/" by default: /docs/my%20file.pdf
print(urlencode({"q": "rock & roll", "page": 2}))  # q=rock+%26+roll&page=2
print(unquote("caf%C3%A9"))                 # café

Go: net/url

package main

import (
	"fmt"
	"net/url"
)

func main() {
	fmt.Println(url.QueryEscape("a&b=c d/é")) // a%26b%3Dc+d%2F%C3%A9 (space as +)
	fmt.Println(url.PathEscape("my file.pdf")) // my%20file.pdf

	v := url.Values{}
	v.Set("q", "rock & roll")
	v.Set("page", "2")
	fmt.Println(v.Encode()) // page=2&q=rock+%26+roll (keys sorted)

	s, _ := url.QueryUnescape("caf%C3%A9")
	fmt.Println(s)
}

Each snippet was run on October 14, 2026 with Node.js 20, Python 3.14 and Go 1.24.

URL encoding specs: RFC 3986 and WHATWG

• RFC 3986: URI Generic Syntax
• RFC 3986, section 2.1: percent-encoding
• RFC 3986, section 2.3: unreserved characters: A-Z a-z 0-9 - . _ ~ never need encoding
• WHATWG URL Standard: application/x-www-form-urlencoded: the form rules where a space becomes +
• MDN: encodeURIComponent()
• Python docs: urllib.parse
• Go docs: net/url

FAQ