SEO & GEO glossary
71 definitions of the vocabulary you will hear in a pitch, an audit or a reporting meeting — from crawl budget to AI Overviews. Every entry answers the question first, then explains why it matters and what it changes in practice.
C
Canonical tag
A canonical tag tells search engines which URL is the preferred version of duplicate or near-duplicate pages, consolidating their ranking signals onto one address.
CLS (Cumulative Layout Shift)
CLS measures how much visible content moves unexpectedly while a page loads. Good is under 0.1. It is the metric users feel as tapping the wrong button.
Core Web Vitals
Core Web Vitals are three field-measured user experience metrics: Largest Contentful Paint (loading), Interaction to Next Paint (responsiveness) and Cumulative Layout Shift (visual stability).
Crawl budget
Crawl budget is the number of URLs a search engine is willing and able to fetch from a site in a given period. It only becomes a constraint on large or slow sites.
Crawling
Crawling is the process by which a search engine's robot discovers URLs and downloads their content, following links and sitemaps across the web.
D
F
H
hreflang
hreflang is an annotation declaring that several URLs are the same page in different languages or regions, so search engines serve the right version to the right audience.
HTTP status code
A status code is the server's three-digit answer to a request: 200 for success, 301 and 302 for redirects, 404 for not found, 410 for gone, 5xx for server failures.
I
Indexing
Indexing is a search engine's decision to store a crawled page and make it eligible to appear in results. A page that is not indexed cannot rank, whatever its quality.
INP (Interaction to Next Paint)
INP measures how quickly a page visually responds to user interactions across the whole visit. It replaced First Input Delay in March 2024. Good is under 200 milliseconds.
L
LCP (Largest Contentful Paint)
LCP measures how long it takes for the largest visible element — usually a hero image, a video poster or a block of text — to render. Good is under 2.5 seconds.
Log file analysis
Log file analysis reads the server's own record of every request to see exactly which URLs search engine crawlers fetched, how often, and what status codes they received.
N
P
R
Redirect (301, 302)
A redirect sends a request for one URL to another. A 301 signals a permanent move and consolidates signals; a 302 signals a temporary one and keeps the original indexed.
Rendering (SSR, CSR, hydration)
Rendering is how HTML reaches the browser: built on the server (SSR), built in the browser by JavaScript (CSR), or pre-built at deploy time. It determines whether crawlers can see your content.
robots.txt
robots.txt is a file at the root of a domain that tells crawlers which paths they may request. It controls crawling, not indexing, and it is public.
S
Site migration
A migration is any change to a site's domain, URL structure, platform or content organisation. It is the highest-risk event in SEO and the most often under-planned.
Structured data (schema.org)
Structured data is machine-readable markup, usually JSON-LD following schema.org vocabulary, that states what a page is about: a product, an article, an organisation, an FAQ.