URL Encoder / Decoder

How to Use the URL Encoder / Decoder

This free URL encoding tool converts special characters in text to their percent-encoded equivalents, making them safe for use in URLs. It can also decode percent-encoded strings back to readable text. All processing is done locally in your browser.

What is URL Encoding?

URL encoding (also called percent-encoding) replaces unsafe characters with a percent sign followed by two hexadecimal digits. For example, a space becomes %20, and an ampersand becomes %26. This ensures that URLs are transmitted correctly across the internet without ambiguity.

When Do You Need URL Encoding?

URL encoding is necessary whenever you include user input in URLs, pass special characters as query parameters, build API request URLs programmatically, or encode file names that contain spaces or special characters. Without proper encoding, URLs may break or be interpreted incorrectly by web servers.

Characters That Need Encoding

Reserved characters like ?, &, =, #, and / have special meaning in URLs and must be encoded when used as data. Unsafe characters such as spaces, quotes, and angle brackets should always be encoded. This tool handles all of these automatically using the standard encodeURIComponent function.

URLエンコーダー/デコーダーの使い方

「エンコード」または「デコード」モードを選択し、テキストを入力してボタンを押すだけでURLエンコード・デコードができます。 スペースや特殊文字、日本語などのUnicode文字も正しく処理されます。APIのクエリパラメータ作成やURLデバッグに便利です。 全ての処理はブラウザ内で完結し、データが外部に送信されることはありません。

よくあるエラーと対処 / Common Errors and Fixes

言語別コード例 / Code Examples

JavaScript

encodeURIComponent("東京&大阪")  // "%E6%9D%B1%E4%BA%AC%26%E5%A4%A7%E9%98%AA"
decodeURIComponent("%E6%9D%B1%E4%BA%AC")  // "東京"
// URLSearchParams なら自動でエンコードされる
new URLSearchParams({ q: "東京&大阪" }).toString()

Python

from urllib.parse import quote, unquote, urlencode
quote("東京&大阪", safe="")        # 値のエンコード
urlencode({"q": "東京&大阪"})       # クエリ文字列の組み立て

Shell (curl)

curl -G --data-urlencode "q=東京 大阪" https://example.com/search
# --data-urlencode が自動でエンコードしてくれる

Go

import "net/url"
url.QueryEscape("東京&大阪")   // クエリ値用
url.PathEscape("東京/大阪")    // パスセグメント用(/もエンコード)

変換例 / Before & After

"hello world"   → "hello%20world"
"東京"           → "%E6%9D%B1%E4%BA%AC"  (UTF-8の3バイトを%表記)
"a&b=c"         → "a%26b%3Dc"           (構造文字のエスケープ)
"100%"          → "100%25"              (%自体は%25)

Why browser-only?

URLs frequently embed sensitive data: session tokens, API keys in query strings, internal hostnames, or user identifiers. Pasting them into a server-backed encoder hands all of that to a third party. This tool uses the browser's built-inencodeURIComponent/decodeURIComponent — every conversion happens on your machine, nothing is transmitted, and it works offline. Verify in the DevTools Network tab.

URLにはセッショントークンやAPIキーが含まれがちです。本ツールは変換の全てがブラウザ内で完結し、 入力したURLが外部に送信されることはありません。