Technical SEO focuses on how well search engines can crawl, index, and understand your website. This glossary explains the most important technical terms in plain English, so you can identify and fix issues that affect your rankings and site performance.
A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z
A
Algorithm update
When Google changes how it ranks websites. Updates can affect traffic if your site relies on factors that have been devalued.
AMP (Accelerated Mobile Pages)
A lightweight web format designed to load pages faster on mobile devices. Once popular, but now used less since most sites are mobile-friendly.
API (Application Programming Interface)
A system that allows different tools or platforms to communicate, such as connecting analytics or SEO software to your website.
B
Breadcrumbs
Navigation links that show users where they are within your site structure. They also help search engines understand hierarchy.
Broken link
A link that no longer works, often because the destination page has been deleted or moved. Too many broken links can harm user experience and SEO.
Browser caching
Storing static website files (like images or CSS) in a visitor’s browser so pages load faster on repeat visits.
C
Canonical tag
A tag that tells search engines which version of a page is the “main” one when duplicate or similar content exists.
CDN (Content Delivery Network)
A network of servers around the world that stores and delivers website content closer to users, improving load times.
CLS (Cumulative Layout Shift)
One of Google’s Core Web Vitals. It measures how much content moves unexpectedly as a page loads — a low CLS means a stable layout.
Crawl budget
The amount of time and attention Googlebot gives your site when crawling. Wasting it on duplicate or low-value pages can slow indexing.
Crawl error
When a search engine tries to access a page but can’t, due to broken links, redirects, or blocked files.
Crawlability
How easily search engines can navigate your website. A crawlable site has no major barriers, broken links, or blocked sections.
D
DNS (Domain Name System)
Translates your website’s domain name into an IP address so browsers can find it. Slow DNS can delay page loading.
Duplicate content
Text or pages that appear in more than one place. It can confuse search engines and weaken ranking signals.
Data structure
The way information is organised in your website’s code. Good structure helps both users and crawlers understand relationships between pages.
De-indexing
When a page is removed from Google’s index, either intentionally or due to errors like “noindex” tags or poor quality content.
E
Error 404
The message users see when they visit a broken or missing page. Custom 404 pages can guide users back to active content.
External link
A hyperlink that leads from your website to another domain. Linking to relevant, authoritative sources supports SEO credibility.
F
Fetch as Google
An old Google Search Console feature (now called “URL Inspection”) used to test how Google crawls a page.
First Input Delay (FID)
A Core Web Vital metric that measures how quickly a page responds when someone first interacts with it.
Flat site structure
A structure where important pages are only a few clicks from the homepage. This helps crawlers reach everything easily.
Favicon
The small icon that appears in browser tabs. It’s a small branding element but also contributes to user trust and professionalism.
G
Googlebot
Google’s web crawler that discovers and indexes pages. Making your site accessible to Googlebot ensures your content can be ranked.
GSC (Google Search Console)
A free tool from Google for monitoring your site’s indexing, performance, and technical health.
GZIP compression
A method of reducing file sizes on your server to speed up page loading times.
H
Hreflang
A tag that tells Google which language or regional version of a page to show to users in different countries.
HTTP / HTTPS
Protocols for transferring data between browsers and servers. HTTPS is secure and now a ranking signal for Google.
HTTP status code
Numbers that tell browsers how a page request was handled. For example, 200 means OK, 301 means redirected, 404 means not found.
Headless CMS
A content management system where the front end (design) and back end (data) are separated, allowing faster and more flexible site builds.
I
Index
Google’s database of all web pages it knows about. Only indexed pages can appear in search results.
Indexability
Whether or not a page can be added to Google’s index. Factors like “noindex” tags or blocked robots.txt can prevent indexing.
Internal link
A link from one page on your website to another. Internal links guide both users and search engines through your site structure.
IP address
A unique number identifying your website’s server on the internet. It helps browsers find where your site is hosted.
J
JavaScript
A coding language that adds interactivity to web pages. If not implemented properly, it can block crawlers or delay content rendering.
JSON-LD
A structured data format used to add schema markup to web pages, helping search engines understand their content better.
K
Keyword cannibalisation
When multiple pages on your site compete for the same keyword, causing Google to struggle choosing which one to rank.
L
Lazy loading
A technique that delays loading images or videos until they appear on screen, improving page speed.
Load time
How long a page takes to fully display. Slow load times can increase bounce rate and hurt rankings.
Log file
A file that records every request made to your web server. Analysing logs helps you see how crawlers move through your site.
Link equity
The ranking value or “authority” passed through links from one page to another. Internal linking helps distribute link equity efficiently.
M
Meta robots tag
Code that tells search engines how to handle a page — for example, whether to index it or follow its links.
Mobile-first indexing
Google primarily uses the mobile version of your site for indexing and ranking, so mobile optimisation is essential.
Minification
The process of removing unnecessary characters (like spaces and comments) from code files to reduce size and speed up load times.
Mirror site
An identical copy of a website hosted at a different address. It’s sometimes used for backups or international versions but can cause duplication issues.
N
Navigation depth
How many clicks it takes to reach a page from the homepage. Shallow navigation helps crawlers discover content faster.
Noindex
A tag that tells search engines not to include a page in search results. Often used for thank-you pages or admin areas.
Nofollow
An attribute on a link that tells search engines not to pass authority to the linked page. Used for paid or user-generated links.
O
Orphan page
A page that isn’t linked to from anywhere else on your site. Orphan pages are hard for search engines and users to find.
Open Graph tags
Meta tags that control how your content looks when shared on social media — title, image, and description.
Outdated content
Information that’s no longer accurate or relevant. Regular updates help maintain trust and visibility.
P
Page speed
How fast your website loads. Faster pages improve user experience and rankings.
Page experience
Google’s measurement of how enjoyable a page is to use — factoring in Core Web Vitals, HTTPS, and mobile friendliness.
Pagination
Dividing long lists of content (like blog posts or products) into separate pages to make them easier to browse and crawl.
Penalty
A ranking drop caused by breaking Google’s guidelines. Penalties can result from manipulative links or low-quality content.
Protocol
The set of rules that allow data to be transferred online — such as HTTP, HTTPS, or FTP.
Q
Query parameter
Extra information added to a URL after a question mark, often used for tracking or filters (e.g. ?source=google).
R
Redirect
A way to send users and search engines from one URL to another. A 301 redirect is permanent; a 302 is temporary.
Rendering
The process of turning code into visible content on a screen. Some JavaScript-heavy sites delay rendering, affecting SEO.
Robots.txt
A file that tells search engines which parts of your site they can or can’t crawl.
Response time
The time your server takes to respond to a user or crawler request. Lower response times improve performance.
S
Schema markup
Structured data added to your pages to help search engines understand your content and show rich results like stars or FAQs.
Search Console
Google’s free tool for monitoring site performance, coverage issues, and indexing health.
Server
The computer that hosts your website and delivers content to visitors when they access it.
Site architecture
How your website’s pages are organised and linked together. A clear architecture helps users and search engines navigate efficiently.
Sitemap
A file (usually XML) listing all the important pages on your site to help search engines find and crawl them.
Soft 404
A page that looks like an error page but still returns a 200 (OK) status. It confuses search engines and should be fixed.
SSL certificate
A security layer that encrypts data sent between your site and visitors. Sites with HTTPS use SSL certificates.
Structured data
Code that helps search engines interpret your content, such as identifying reviews, FAQs, or products.
T
Technical audit
A detailed check of your website’s structure, speed, and crawl health to identify SEO issues.
Thin content
Pages with very little useful information. Google may ignore or de-rank them.
Title tag
The HTML title of a web page that appears in search results. It’s one of the strongest on-page ranking signals.
Tokenisation
Breaking text into small chunks (tokens) that search engines use to analyse meaning and intent.
U
URL structure
The format of your website’s addresses. Clear, descriptive URLs help both users and search engines.
Usability
How easy it is for people to use your website. Good usability improves engagement and reduces bounce rates.
User agent
Software that retrieves and displays content for users — for example, a browser or a search engine crawler.
V
Validation
Checking your website’s code for errors to ensure it meets web standards. Clean code helps with accessibility and SEO.
Viewport
The visible area of a webpage within the browser. Responsive design adjusts layout automatically to fit different viewports.
Virtual hosting
Running multiple websites on a single server. Each has its own domain name but shares the same resources.
W
Web Core Vitals
Google’s performance metrics: LCP (Largest Contentful Paint), FID (First Input Delay), and CLS (Cumulative Layout Shift).
Web crawling
The process search engines use to discover new or updated pages by following links across the web.
Website speed
The time it takes for pages to load fully. Speed affects SEO, user experience, and conversions.
WordPress
A popular content management system used for building websites. Technical SEO settings in WordPress can be managed with plugins like Rank Math.
X
XML sitemap
A structured file that lists your website’s key pages, helping search engines crawl and index them efficiently.
Y
YMYL (Your Money or Your Life)
Google’s term for content that can impact people’s finances, health, or safety. YMYL sites are held to higher quality standards.
Z
Zero-click searches
Search results where users get their answers directly on the results page without clicking any link, often due to featured snippets or maps.