Glossary

Website-health glossary

The terms that come up when you work on a site’s technical health, defined in plain English — status codes, redirects, SSL and TLS, DNS, crawl budget, Core Web Vitals, and the rest. Short, accurate, and linked to the tools that check each one.

3

301 redirect

A permanent redirect that passes ranking signals to the new URL.

302 redirect

A temporary redirect that keeps the original URL indexed.

4

403 Forbidden

A status code meaning the server refuses access to an existing resource.

404 error

A status code meaning the requested page could not be found.

410 Gone

A status code meaning a page was removed on purpose and will not return.

5

503 Service Unavailable

A status code meaning the server is temporarily unable to respond.

B

Broken link

A link that points to a URL that can no longer be reached.

C

Canonical URL

The version of a page you tell search engines to treat as the original.

CDN

A network of servers that caches content close to users for speed.

Core Web Vitals

Google's set of metrics for loading, interactivity, and visual stability.

Crawl budget

How many of a site's URLs a search engine will crawl in a given period.

D

DNS

The system that translates domain names into IP addresses.

Domain expiry

The date a domain-name registration lapses if not renewed.

H

HSTS

A header that forces browsers to use HTTPS for a site.

HTTP status code

A three-digit code a server returns to summarize how a request went.

HTTPS

HTTP carried over an encrypted TLS connection.

I

Indexing

When a search engine stores a page so it can appear in results.

L

Latency

The delay between a request being sent and a response beginning.

Link equity

The ranking value that flows through a link from one page to another.

M

Mixed content

An HTTPS page that loads some resources over insecure HTTP.

R

Redirect

A response that sends a request from one URL to another.

Redirect chain

A sequence of redirects where one URL points to another, then another.

robots.txt

A file telling crawlers which parts of a site they may or may not crawl.

S

Sitemap

An XML file listing a site's URLs to help search engines find them.

Soft 404

A missing page that returns 200 OK instead of a real 404 status.

SSL certificate

A digital certificate that enables HTTPS and proves a site's identity.

T

TLS

The protocol that encrypts traffic between a browser and a server.

TTFB

Time to First Byte: how long until the first byte of a response arrives.

U

Uptime

The proportion of time a site is reachable and serving requests.

User agent

A string identifying the client making an HTTP request.

Sitewell tools

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