SEO Audit Terms Explained: A Plain-English Glossary

A website SEO audit often arrives as a long report full of unfamiliar vocabulary. Without the definitions, it is hard to tell which findings are urgent and which are housekeeping.

This glossary covers the SEO audit terms you are most likely to see. Each entry explains what the term means, why it matters and what a typical finding looks like.

Crawling and indexing terms

Crawlability

Crawlability is whether a search engine’s crawler can reach and fetch your pages. Crawlers follow links and read your XML sitemap to find URLs.

If a page cannot be crawled, nothing else in the audit matters for that page.

Indexability

Indexability is whether a crawled page is allowed and likely to be stored in the search engine’s index. Only indexed pages can appear in results.

A page may be crawlable but not indexable because of a noindex directive, a canonical tag pointing elsewhere, or content the search engine considers duplicate or low in value.

One distinction causes frequent mistakes. A robots.txt rule blocks crawling, not indexing. A blocked URL can still appear in results if other sites link to it. To keep a page out of the index, use noindex and leave the page crawlable so the directive can be read.

Canonical tags

A canonical tag tells search engines which URL is the preferred version when several URLs show the same or very similar content. Online stores generate these duplicates constantly through filters, sorting options and tracking parameters.

Points to know:

Search engines treat the canonical tag as a strong hint, not a command.
Each page should point to one canonical URL, and that URL should load successfully and be indexable.
Most unique pages should carry a self-referencing canonical.

Redirects

A redirect sends visitors and crawlers from one URL to another.

A 301 redirect signals a permanent move. Search engines transfer the old URL’s signals to the new one.
A 302 redirect signals a temporary move. The original URL is generally kept in the index.

Audits often flag redirect chains, where one URL redirects to a second that redirects to a third, and redirect loops, where URLs redirect back to each other. Chains slow down loading and waste crawler effort. Loops make the page unreachable. The fix is to point each old URL directly at its final destination.

Core Web Vitals

Core Web Vitals are three metrics Google uses to measure real-world page experience. They are assessed from actual visitor data, and a page is evaluated at the 75th percentile of visits, so most users must have a good experience for the page to pass.

Metric	What it measures	“Good” threshold
LCP, Largest Contentful Paint	How quickly the main content appears	2.5 seconds or less
INP, Interaction to Next Paint	How quickly the page responds to interactions	200 milliseconds or less
CLS, Cumulative Layout Shift	How much the layout moves unexpectedly	0.1 or less

LCP

LCP marks when the largest visible element, usually a hero image or main heading, finishes rendering. Slow server response, large unoptimized images and render-blocking scripts or stylesheets are the usual causes.

INP

INP measures the delay between a user action, such as a click, tap or key press, and the next visual update. It replaced First Input Delay as a Core Web Vital in 2024. Heavy JavaScript that keeps the browser’s main thread busy is the typical culprit.

CLS

CLS scores unexpected movement of content while the page loads. Images without set dimensions, late-loading ads and embeds, and web fonts that swap in are common sources. Reserving space for each element prevents the shift.

Structured data

Structured data is code added to a page that describes its content in a format machines can read reliably. The standard vocabulary is Schema.org, and the usual format is JSON-LD.

It can label a page as a product, an article, a local business, an FAQ, an event and many other types. This helps search engines understand the page and can make it eligible for enhanced listings, known as rich results, such as review stars or product details.

Two cautions apply. Valid markup makes a page eligible for rich results; it does not ensure they will be shown. And the markup must describe content that is visible on the page.

Hreflang

Hreflang is an attribute that tells search engines which language or regional version of a page to show to which audience. It applies only if your site has multiple versions of the same content, for example English and Spanish editions.

Hreflang is easy to get wrong. Each version must list all the others and itself, and the references must be reciprocal. If page A points to page B, page B must point back. Language codes must be valid. An x-default value can name the fallback version for everyone else.

Backlinks

A backlink is a link from another website to yours. Search engines treat links as a signal of trust and relevance, and they remain an important ranking factor.

Terms you will see in this part of an audit:

Referring domains: the number of distinct websites linking to you. This is usually more meaningful than the raw link count.
Nofollow, sponsored and UGC: attributes that tell search engines how to treat a link, for instance paid links or links in user comments.
Toxic or spammy links: links from low-quality sources. Search engines ignore most of these on their own, so mass disavowal is rarely necessary.
Authority scores: metrics created by SEO tool vendors. They are useful for comparison but are not used by Google.

Buying links violates search engine guidelines and carries real risk.

E-E-A-T

E-E-A-T stands for Experience, Expertise, Authoritativeness and Trustworthiness. It comes from the guidelines Google gives to its human quality raters.

E-E-A-T is not a single score or a direct ranking factor. It is a framework describing the qualities Google’s systems are designed to reward. It carries the most weight for topics that affect health, finances or safety.

Visibility in AI search

Search now includes AI-generated answers, both inside traditional search engines and in assistants such as ChatGPT, Perplexity and Google’s AI features. Newer audits assess how well a site is positioned for them.

The foundations are the same as for classic SEO. An AI system must be able to crawl your content, understand it and consider it trustworthy before it will cite it. Specific checks include:

Whether your robots.txt allows or blocks the crawlers used by AI services, which is a business decision you should make deliberately
Whether key content is present in the HTML rather than hidden behind scripts
Whether pages answer questions directly, with clear headings and concise, factual statements

How to prioritize audit findings

Not every flagged item deserves equal effort. A sensible order:

Access problems: crawl blocks, accidental noindex, server errors and broken redirects on important pages.
Duplication and canonical issues that split signals between URLs.
Core Web Vitals failures on high-traffic templates.
Content and E-E-A-T improvements on the pages that drive revenue.
Enhancements such as structured data and minor warnings.

Key takeaways

Crawlability is whether search engines can reach a page. Indexability is whether they can store it. Both must be true before a page can rank.
Use noindex, not robots.txt, to keep a page out of search results.
Canonical tags consolidate duplicate URLs. Redirects should go straight to the final destination with a 301 for permanent moves.
Core Web Vitals are LCP, INP and CLS, judged on real visitor data.
Structured data helps search engines understand content and qualifies pages for rich results.
E-E-A-T is a quality framework, not a score. Backlink quality matters more than quantity.
AI search visibility builds on the same technical and content foundations as traditional SEO.

iSky Creative runs technical audits as part of its SEO services, and you can contact us for help interpreting your report.