特殊文字を URL エンコードする方法

问题

URL にスペース、アンパサンドなどの特殊文字が含まれており、クエリ文字列の構造が壊れています。

前提条件

• URL 構造の基礎知識
• パーセントエンコーディングの理解

ステップ

1. 1. Identify unsafe characters

   Characters like space, &, =, ?, #, and + have special meaning in URLs. Leaving them unencoded will change how the server parses the query string. Review your input and flag every reserved or non-ASCII character.

   入力

   name=John Doe & Co.

   输出

   unsafe: space, &

2. 2. Percent-encode each character

   Replace each unsafe character with a percent sign followed by its two-digit UTF-8 hex byte. A space becomes %20, an ampersand becomes %26, and a non-ASCII character may produce multiple percent sequences.

   入力

   name=John Doe & Co.

   输出

   name=John%20Doe%20%26%20Co.

3. 3. Verify the encoded URL

   Paste the encoded URL into a browser or HTTP client. The server should receive the original string exactly. If any character is still raw, the encoding was incomplete.

   入力

   name=John%20Doe%20%26%20Co.

   输出

   server receives: name=John Doe & Co.

期待される結果

標準準拠のサーバーならどれでも曖昧さなくパースできる、完全にパーセントエンコードされた URL。

よくあるエラー

Encoding the entire URL including the scheme and host

Only encode the query parameter values and path segments, not the protocol or domain.

Double-encoding an already-encoded string

Check for existing % sequences before encoding. Decode first if you need to re-encode.

トラブルシューティング指引

• If the server receives literal %20 instead of a space, the string was double-encoded.
• Use encodeURIComponent in JavaScript for query values, not encodeURI.

セキュリティ上の制限

• URL encoding prevents parsing errors but does not prevent injection. Validate and sanitize all input on the server side.