What Is URL Encoding?
URL encoding — also called percent encoding — is a mechanism defined in RFC 3986 for representing arbitrary data within a Uniform Resource Identifier. When a URL contains characters that are either reserved (such as &, =, ?, and #) or unsafe for transmission (such as spaces, non-ASCII characters, and control bytes), those characters must be replaced with a percent sign followed by their two-digit hexadecimal code point. For example, a space becomes %20, an ampersand becomes %26, and a Chinese character like 你 becomes its UTF-8 bytes encoded as %E4%BD%A0.
The distinction between reserved and unreserved characters is central to percent encoding. Unreserved characters — A through Z, a through z, 0 through 9, hyphen, underscore, period, and tilde — are safe to use as-is everywhere in a URL. Everything else must be encoded when it appears as data rather than as a structural delimiter. This rule matters most for query parameter values: a value containing an unescaped & would be misread as the start of a new parameter.
JavaScript provides two built-in functions for this purpose: encodeURIComponent encodes everything except unreserved characters and is the correct choice for individual query parameter keys and values; encodeURI preserves the structural characters (/, :, ?, #, &) and is meant for encoding a full URL that is already well-formed. The url encoder and url decoder on this page apply encodeURIComponent-style percent encoding by default. For binary payloads carried in a query string, reach for the Base64 Converter instead, and use the JSON Formatter when a parameter holds an encoded JSON object.
▶How to URL Encode or Decode a String Online
- 1Paste your text. Enter a URL with special characters to encode, or a percent-encoded string to decode.
- 2Choose mode. Select URL Encode or URL Decode.
- 3Copy the result. The converted string appears instantly. Click copy to use it.
▶Encoding Query Parameters and Double Encoding
Paste the text you want to encode into the input field and select Encode. Every character outside the unreserved set is immediately replaced with its percent-encoded equivalent. To reverse the process, paste a percent-encoded string and select Decode — the tool reconstructs the original bytes and interprets them as UTF-8 text.
For query parameters, always encode the value alone, not the entire URL. Encoding https://example.com/search?q=hello world as a whole will corrupt the structural slashes and colon; instead encode only hello world to get hello%20world and then assemble the URL. If your string has already been encoded once and you see sequences like %2520 (a double-encoded percent sign), run decode twice to recover the original text.
▶Code Examples
▶JavaScript / TypeScript
// encodeURIComponent — encode a single query parameter value
const query = "hello world & more";
console.log(encodeURIComponent(query));
// "hello%20world%20%26%20more"
// encodeURI — encode a complete URL, preserving structural characters
const url = "https://example.com/search?q=hello world";
console.log(encodeURI(url));
// "https://example.com/search?q=hello%20world"
// Decode
console.log(decodeURIComponent("hello%20world%20%26%20more"));
// "hello world & more"▶Python
from urllib.parse import quote, unquote, urlencode
# Encode a single value (safe='' encodes everything including /)
value = "hello world & more"
print(quote(value, safe=""))
# "hello%20world%20%26%20more"
# Encode a dict of query parameters
params = {"q": "hello world", "lang": "en"}
print(urlencode(params))
# "q=hello+world&lang=en"
# Decode
print(unquote("hello%20world%20%26%20more"))
# "hello world & more"▶Go
package main
import (
"fmt"
"net/url"
)
func main() {
// Encode a query parameter value
value := "hello world & more"
encoded := url.QueryEscape(value)
fmt.Println(encoded) // "hello+world+%26+more"
// url.PathEscape preserves slashes, suitable for path segments
path := url.PathEscape("path/to my file")
fmt.Println(path) // "path%2Fto%20my%20file"
// Decode
decoded, _ := url.QueryUnescape(encoded)
fmt.Println(decoded) // "hello world & more"
}▶Bash
# Encode with curl (writes encoded form to stdout)
curl -Gso /dev/null -w "%{url_effective}" --data-urlencode "q=hello world & more" "https://example.com" | cut -c2-
# ?q=hello%20world%20%26%20more
# Encode using printf + xxd (portable, no curl required)
printf '%s' "hello world" | xxd -plain | tr -d '
' | sed 's/\(..\)/%\1/g'
# %68%65%6c%6c%6f%20%77%6f%72%6c%64
# Decode with Python one-liner (available on most systems)
python3 -c "import sys, urllib.parse; print(urllib.parse.unquote(sys.argv[1]))" "hello%20world%20%26%20more"
# hello world & more▶Frequently Asked Questions
▶What is URL encoding (percent encoding)?
URL encoding replaces unsafe characters in a URL with a percent sign (%) followed by two hexadecimal digits. For example, a space becomes %20 and an ampersand becomes %26.
▶When should I URL encode a string?
You should URL encode any string that will be used as a query parameter, path segment, or fragment — especially if it contains spaces, special characters (&, =, ?, #), or non-ASCII characters like Chinese or emoji.
▶What is the difference between encodeURI and encodeURIComponent?
encodeURI encodes a full URL but preserves characters like :, /, ?, and #. encodeURIComponent encodes everything except A-Z, a-z, 0-9, and a few symbols, making it suitable for encoding individual query parameter values.
▶Can this tool decode double-encoded URLs?
Yes. If your URL has been encoded multiple times (e.g., %2520 instead of %20), you can decode it repeatedly until you get the original text.