SEO glossary: every term explained in plain English

SEO is full of jargon. Here's what each term means in a sentence or two, with a link to a free tool or guide where you can see it in action on your own site.

Last updated · By the XKey team

Jump to: # · A · B · C · D · E · F · G · H · I · J · K · L · M · N · O · P · R · S · T · U · W · X · Z

0–9

301 redirect – A permanent redirect from one address to another. It passes almost all of the old page's ranking value to the new one, so use it whenever a page moves. Redirect checker

302 redirect – A temporary redirect. Search engines keep the old address in their index, so don't use it for permanent moves.

404 error – The 'page not found' response. A few are normal; links from your own pages to 404s waste visitors and crawling. Broken link checker

A

AI Overviews – AI-written summaries Google shows above some search results, with links to the pages they draw on.

Algorithm update – A change Google makes to how it ranks pages. Big 'core updates' happen a few times a year and can move rankings up or down.

Alt text – A short description of an image in the page code. Screen readers read it aloud, and Google uses it to understand the picture. Image SEO guide

Anchor text – The clickable words of a link. Descriptive anchor text tells Google and visitors what the linked page is about. Anchor text checker

Authority – An estimate of how strong a website is, based on the links pointing to it. Each SEO tool has its own score; Google doesn't publish one. Domain authority checker

B

Black hat SEO – Tactics that break search engines' rules – hidden text, bought links, fake reviews. They risk penalties and rarely last.

Bounce rate – In older analytics, the share of visits that left after one page. Google Analytics 4 uses 'engagement rate' instead.

C

Canonical tag – A line in the page code that names the main version of a page when the same content is reachable at several addresses. Duplicate content guide

Citation – A mention of your business name, address and phone number on another site, such as a directory. Important for local SEO. Directory listings guide

Click-through rate (CTR) – The share of people who saw your result in Google and clicked it. Better titles and descriptions raise it.

CLS (Cumulative Layout Shift) – How much a page jumps around while it loads. Under 0.1 is good.

CMS – Content management system – the software you edit your website with, such as WordPress, Wix or Shopify. Technology checker

Content gap – Topics your competitors cover that you don't. Filling them can win searches you're missing. Competitor comparison

Conversion rate – The share of visitors who do what you want – call, book, buy or send an enquiry. More traffic only helps if pages convert.

Core update – A broad change to Google's ranking systems, announced a few times a year.

Core Web Vitals – Google's three measures of real-world page experience: loading (LCP), responsiveness (INP) and visual stability (CLS). Core Web Vitals guide

Crawl budget – Roughly how many pages Google is willing to crawl on your site in a given time. Only matters for very large sites.

Crawler – A program that visits web pages to read them, such as Googlebot or Bingbot. Also called a spider or bot. Website crawler

D

Deindexed – Removed from Google's index, so the page can't appear in results.

DKIM – A digital signature on your emails that proves they came from your domain. Not an SEO factor, but vital for email delivery. DKIM checker

DMARC – An email DNS record that says what to do with mail that fails SPF and DKIM checks. DMARC checker

DNS – The internet's address book: it turns your domain name into the server address your site lives on. DNS lookup

Domain age – How long ago a domain was first registered. Age alone isn't a ranking factor, but older sites have had longer to earn links. Domain age checker

Domain authority – Moz's name for its 0–100 link strength score, now used loosely for any tool's authority score. What is domain authority?

Duplicate content – The same or very similar text on several pages or sites. Google usually shows only one version. Duplicate content guide

E

E-E-A-T – Experience, Expertise, Authoritativeness and Trustworthiness – the qualities Google's quality raters look for in content. What is E-E-A-T?

F

Favicon – The small icon shown in browser tabs and next to your site in Google's mobile results.

G

Google Business Profile – Your free business listing on Google Search and Maps – the most important thing for local SEO. Google Business Profile guide

Google Search Console – Google's free tool showing which searches you appear for, clicks, indexing problems and more. Search Console guide

Googlebot – Google's crawler. It reads pages much like a modern Chrome browser.

H

H1 heading – The main heading of a page. Each page should have one that says what the page is about.

Headings (H2–H6) – Subheadings that break a page into sections and help readers and search engines scan it.

Hreflang – Tags that tell Google which language or country each version of a page is for. Hreflang checker

HTTPS – The secure version of a web address, shown with a padlock. A light ranking signal and essential for trust. SSL checker

I

Impressions – How many times your pages appeared in search results, whether or not anyone clicked.

Index – Google's database of pages it can show in results. A page must be indexed to rank.

Indexing – Google adding a page to its index after crawling it. Not on Google? Causes and fixes

IndexNow – A way to tell Bing and some other search engines instantly when pages change. Google doesn't use it.

INP (Interaction to Next Paint) – How quickly a page responds when someone taps or clicks. Under 200 milliseconds is good.

J

JSON-LD – The format Google recommends for structured data: a block of code describing the page's content. Schema generator

K

Keyword – A word or phrase people type into a search engine. Keyword research guide

Keyword cannibalisation – Several of your own pages competing for the same search, so none ranks as well as one strong page would.

Keyword difficulty – An estimate of how hard it would be to reach page one for a search. Keyword difficulty checker

Keyword stuffing – Repeating a phrase unnaturally often. Against Google's spam policies and off-putting for readers.

Knowledge panel – The information box Google shows about well-known people, organisations and places.

L

LCP (Largest Contentful Paint) – How long the biggest thing on the screen takes to appear. Under 2.5 seconds is good.

llms.txt – A proposed text file that gives AI tools a summary of your site and its key pages. llms.txt generator

Local pack – The map and three businesses Google shows for local searches such as 'plumber near me'. Local search checker

Local SEO – Getting found by customers searching in your area. Local SEO checklist

Long-tail keyword – A longer, more specific search, such as 'emergency boiler repair Preston'. Easier to rank for and often ready to buy. Keyword generator

M

Manual action – A penalty applied by a person at Google for breaking its spam policies. Shown in Search Console.

Meta description – The page summary in the code that Google often shows under your title in results. Meta descriptions guide

Meta robots tag – A line in the page code that tells search engines whether to index the page and follow its links.

Mobile-first indexing – Google ranks pages using the mobile version of your site, so it must work well on phones.

MX record – The DNS record that says where your domain's email is delivered. MX lookup

N

NAP – Name, address and phone number – they should be identical everywhere your business is listed.

Nofollow – A link attribute (rel="nofollow") asking search engines not to pass ranking value. Also 'sponsored' and 'ugc'.

Noindex – An instruction that keeps a page out of search results.

O

Off-page SEO – Everything outside your site that affects rankings – mainly links, reviews and mentions.

On-page SEO – Optimising the page itself: content, titles, headings, images and links. On-page SEO checklist

Open Graph – Tags that control how your page looks when shared on Facebook, LinkedIn, WhatsApp and others. Open Graph checker

Organic traffic – Visitors who arrive from unpaid search results.

Orphan page – A page that no other page on your site links to, so visitors and search engines struggle to find it.

P

Page speed – How fast a page loads and becomes usable. Page speed checker

PageRank – Google's original method of scoring pages by the links pointing to them. Still part of how Google works, though no longer public.

Penalty – A drop in rankings caused by breaking Google's rules, either automatically or through a manual action.

People Also Ask – The expandable list of related questions Google shows in many results.

Position – Where your page appears in the results – position 1 is the top organic result.

R

Ranking factor – Anything Google uses to decide the order of results, such as relevance, links and page experience.

Redirect chain – Several redirects in a row (A → B → C). Each hop slows things down; link straight to the final page. Redirect checker

Referring domain – A different website that links to yours. Ten links from ten sites usually count for more than ten from one site.

Rich results – Search results with extras such as star ratings, prices or FAQs, made possible by structured data. Schema checker

robots.txt – A file at the root of your site telling crawlers which areas they may visit. robots.txt tester

S

Schema markup – Structured data using the schema.org vocabulary to describe your business, products, events and more. Schema markup guide

Search intent – What the searcher actually wants – to learn, to compare, to buy or to find a place. Pages that match intent rank better.

Search volume – Roughly how many times a month a phrase is searched.

SERP – Search engine results page – the page of results you see after searching.

Site migration – Moving a site to a new domain, platform or structure. Needs redirects for every old address. Redesign without losing rankings

Sitemap (XML) – A file listing the pages you want search engines to find. XML sitemap generator

Slug – The part of a web address after the domain, such as /emergency-plumber. URL slug generator

Soft 404 – A page that says 'not found' (or has almost no content) but returns a normal 200 status, confusing search engines.

Spam score – A tool's estimate of how likely a site is to be penalised, based on spammy patterns. Not a Google measure.

SPF – An email DNS record listing the services allowed to send email as your domain. SPF checker

SSL certificate – The file that lets a site use HTTPS. Free certificates from Let's Encrypt are just as secure as paid ones. SSL checker

Status code – The three-digit answer a server gives for each request: 200 OK, 301 moved, 404 not found, 500 error. HTTP header checker

Structured data – Code that labels the information on a page in a way machines understand. See schema markup.

T

Technical SEO – Making sure search engines can crawl, render and index your site: speed, HTTPS, sitemaps, redirects and so on. Technical SEO checklist

Thin content – Pages with little useful content of their own. Google may ignore them or rank the whole site lower.

Title tag – The page title in the code, shown as the blue link in Google's results. Title tag checker

Top-level domain (TLD) – The ending of a domain, such as .co.uk, .uk or .com. A .co.uk ending helps signal that you serve UK customers. Choosing a domain name

Traffic – The number of visitors to a website.

U

URL – A web address, such as https://xkey.co.uk/seo-tools.

User experience (UX) – How easy and pleasant a site is to use. Good UX keeps visitors and supports rankings.

UTM tags – Labels added to a link so analytics can show where visits came from – a newsletter, a flyer QR code or an advert. UTM builder

W

Webmaster guidelines – Now called Google Search Essentials: Google's rules for sites that want to appear in its results.

White hat SEO – SEO that follows search engines' rules: useful content, a sound site and earned links.

WHOIS – The public record of who a domain is registered with, and when it was registered and expires. WHOIS lookup

Word count – How many words a page has. There's no ideal number – cover the topic fully and stop. Word counter

X

XML sitemap – See sitemap.

Z

Still stuck?

Run the free SEO check on your website – every result in the report explains what it means and how to fix it, in the same plain English. New to SEO? Start with SEO for small businesses, or take the free 10-lesson SEO course.

Frequently asked questions

What does SEO stand for?

Search engine optimisation: making your website easier for search engines like Google to find, understand and recommend.

What's the difference between SEO and SEM?

SEO is about unpaid results. SEM (search engine marketing) usually means paid search adverts such as Google Ads, and sometimes covers both.

Which SEO terms matter most for a small business?

Title tags, Google Business Profile, backlinks, page speed and indexing. Get those right and you're ahead of most competitors.

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