~/devtools / http-status
tool::http-status
HTTPステータス
コード
1xxから5xxまでの全HTTPステータスコードを説明付きで参照・検索できます。
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Client should continue with the request.
Server is switching protocols as requested.
Server has received the request but has not yet completed it.
Used to preload resources while the server is still processing.
The request has succeeded.
The request has been fulfilled and a new resource has been created.
The request has been accepted but not yet acted upon.
The response is from a transforming proxy, not the origin server.
The server successfully processed the request but returns no content.
The server processed the request; the client should reset the document view.
The server is returning partial content due to a Range header.
Multiple status codes for multiple independent operations (WebDAV).
Members of a DAV binding have already been enumerated.
The server fulfilled the request using instance manipulations.
Multiple options for the requested resource.
The resource has permanently moved to a new URL.
The resource is temporarily at a different URL.
Redirect to another resource using GET.
The cached version is still valid; no new content to return.
Temporary redirect preserving the original HTTP method.
Permanent redirect preserving the original HTTP method.
The server could not understand the request due to invalid syntax.
Authentication is required and has failed or not been provided.
Reserved for future use; some services use it for payment walls.
The server refuses to fulfill the request (authenticated but unauthorized).
The requested resource could not be found.
The HTTP method is not supported for this resource.
No content matching the Accept headers is available.
Authentication with a proxy is required.
The server timed out waiting for the request.
The request conflicts with the current state of the server.
The resource has been permanently deleted and will not return.
The Content-Length header is required but not provided.
One or more conditions in the request headers evaluated to false.
The request body exceeds the server's size limit.
The request URI is longer than the server can process.
The media type of the request is not supported.
The range specified in the Range header cannot be fulfilled.
The expectation in the Expect header cannot be met.
The server refuses to brew coffee; it is a teapot (RFC 2324).
The request was directed at a server unable to produce a response.
The request is well-formed but contains semantic errors.
The resource being accessed is locked (WebDAV).
The request failed because a previous request failed (WebDAV).
The server is unwilling to process a potentially replayed request.
The client should switch to a different protocol.
The server requires the request to be conditional.
The user has sent too many requests in a given time (rate limiting).
Request headers are too large for the server to process.
The resource is unavailable due to legal restrictions.
The server encountered an unexpected condition.
The server does not support the requested functionality.
The gateway received an invalid response from an upstream server.
The server is temporarily unable to handle the request.
The gateway did not receive a timely response from an upstream server.
The HTTP version used in the request is not supported.
A circular reference in transparent content negotiation.
The server is unable to store the representation (WebDAV).
An infinite loop was detected while processing the request (WebDAV).
Further extensions to the request are required.
Network authentication is required before accessing resources.
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// about this tool
HTTPステータスコードについて
HTTPステータスコードは、クライアントのリクエストに対するサーバーの応答結果を3桁の数字で表します。最初の桁が応答の分類を示します：1xxは情報、2xxは成功、3xxはリダイレクト、4xxはクライアントエラー、5xxはサーバーエラーです。このシステムはHTTP/1.0（RFC 1945、1996年）で導入され、現在のHTTP/2やHTTP/3にも引き継がれています。
実務で最もよく見かけるコードは200(OK)、201(Created)、301(Moved Permanently)、302(Found)、400(Bad Request)、401(Unauthorized)、403(Forbidden)、404(Not Found)、500(Internal Server Error)です。401と403の違い（認証失敗vs認可拒否）や301と302の違い（永続的vs一時的リダイレクト）は、API設計とSEOに直接影響します。
このツールは1xx〜5xxの標準HTTPステータスコードをカテゴリタブで整理し、コード番号や名前でリアルタイム検索できます。コードをクリックするとクリップボードにコピーされます。REST API設計、サーバーデバッグ、Web開発学習のクイックリファレンスとして活用してください。
主な使用例
- ▸馴染みのないHTTPステータスコードの正確な意味を調べる
- ▸REST API設計時の正しいステータスコード選択
- ▸サーバーやサードパーティAPIのHTTPエラーのデバッグ
- ▸リダイレクトコードの正しい使い方を確認（301 vs 302 vs 307 vs 308）
- ▸認証エラーの区別を確認（401 vs 403）
よくある質問
Q. 401と403の違いは何ですか？
401 Unauthorizedは「認証（Authentication）が必要か失敗した」ことを意味します。サーバーがあなたが誰かを知らない状態です。403 Forbiddenは「認証は成功したが、このリソースへのアクセス権限がない（Authorization失敗）」ことを意味します。誰かは分かっているが許可しないという状態です。
Q. 301と302と307と308の使い分けは？
301(Moved Permanently)と308(Permanent Redirect)は永続的なURL変更に使用し、検索エンジンはリンク評価を新URLに移します。302(Found)と307(Temporary Redirect)は一時的なリダイレクトで、検索エンジンは元のURLをインデックスし続けます。307/308は301/302と異なりリダイレクト時のHTTPメソッドを変更しません。
Q. 418 I'm a Teapotは実際に使われますか？
RFC 2324でエイプリルフールのジョークとして定義されましたが、IANAのHTTPステータスコードレジストリに登録されています。実際のAPIでユーモアある拒否レスポンスとして使われることもありますが、本番環境での使用は推奨されません。技術的には有効で広く認知されています。