SEO・リンク構築用語集
ウェブサイトのリンク管理やテクニカルSEOで遭遇する用語のわかりやすい定義。
404エラー
ページが見つからないとき何が起こるか — そしてSEOへの影響。
301リダイレクト
リンクエクイティを保持しユーザーを導く永続リダイレクト。
クロールバジェット
検索エンジンがサイトのクロールに割り当てるリソース。
リンク切れ
目的のページに到達しなくなったハイパーリンク。
リダイレクトチェーン
ページを遅くしSEO価値を薄める連続リダイレクト。
リンクロット
時間とともにリンクが徐々に壊れていくプロセス。
Dead Link
A hyperlink that points to a page or resource that no longer exists.
Soft 404
A page that returns HTTP 200 but displays error content instead of useful information.
HTTP Status Codes
Three-digit server response codes that indicate the result of an HTTP request.
Anchor Text
The visible, clickable text of a hyperlink that describes where the link leads.
302 Redirect
The temporary redirect — when to use it and how it differs from a 301.
Canonical URL
The preferred version of a page — preventing duplicate content issues.
robots.txt
The file that tells crawlers which parts of your site they can access.
XML Sitemap
The map you give search engines to discover and prioritize your pages.
hreflang
The HTML attribute that tells search engines which language version to serve.
Meta Description
The snippet under your title in search results — what users actually read.
noindex
The directive that keeps a page out of search engine indexes.
nofollow
The link attribute that tells search engines not to pass ranking signals.
Internal Link
Links between pages on the same domain — the backbone of site structure.
External Link
Links pointing to another domain — outbound trust signals.
Backlink
An inbound link from another site — the original ranking signal.
Link Equity
The ranking value passed through links — also known as "link juice".
500 Internal Server Error
The catch-all error returned when a server-side problem prevents page rendering.
503 Service Unavailable
The status code that signals temporary downtime — often used during maintenance.
DNS Error
A failure to resolve a domain name to its server — the request never even starts.
SSL Certificate
The cryptographic credential that enables HTTPS — and that search engines expect.
www vs non-www
Choosing the canonical hostname — and why consistency matters more than the choice itself.
Mixed Content
When an HTTPS page loads HTTP resources — a security and SEO problem.
Redirect Loop
When redirects circle back on themselves and the page never loads.
User-Agent
The HTTP header identifying the client — and what servers use to decide what to serve.