What does a technical SEO audit check?

A technical SEO audit checks whether a website can be crawled, understood and indexed efficiently by search engines, and whether technical problems are preventing important pages from appearing or performing in organic search. It examines the way a site is built, linked, rendered and delivered to users, rather than focusing only on page copy or keyword targeting.

A thorough audit normally reviews the following areas.

Crawlability

Crawlability is the extent to which search engine crawlers can discover and access a website’s pages. An audit checks the robots.txt file for rules that unintentionally block important sections, resources or page types. It also examines crawl paths, orphan pages, excessive URL variations and crawl traps such as calendar pages, filter combinations or endlessly generated parameters.

The audit may compare pages found through crawling with pages listed in XML sitemaps and pages recorded in search engine data. Differences can reveal important URLs that are difficult to discover, outdated sitemap entries or areas that are being crawled unnecessarily.

Indexing and indexation controls

Being crawlable does not guarantee that a page will be indexed. The audit checks whether valuable pages are eligible for inclusion in search results and whether directives are sending the correct signals. This includes noindex instructions, canonical tags, X-Robots-Tag headers, blocked resources and pages that search engines have discovered but chosen not to index.

It also looks for accidental indexation of low-value or inappropriate URLs, such as internal search results, duplicate filter pages, test environments, thin utility pages and outdated content. The aim is not to have every URL indexed; it is to ensure that the pages intended to attract organic traffic are accessible, understandable and supported by consistent signals.

HTTP status codes and technical errors

Every URL returns a response that helps search engines interpret its condition. An audit identifies broken pages returning not-found responses, server errors, redirect chains, redirect loops and unexpected soft errors where a page appears to be missing but returns a successful response.

Redirects are checked to confirm that retired or moved URLs lead to the most relevant replacement. Redirects should not be used to conceal broken navigation or send users through several unnecessary hops. The audit also checks whether internal links, canonical tags and XML sitemaps point directly to the preferred live URL instead of to redirected or broken addresses.

Site architecture and URL structure

Search engines use the site’s structure to understand relationships between pages and to assess which content is important. A technical audit reviews navigation, directory depth, URL consistency and the relationship between key landing pages and supporting content.

URLs are checked for avoidable duplication caused by capitalisation, trailing slashes, parameters, session identifiers, alternate protocols or different hostnames. The preferred format should be clear and consistently referenced across internal links, canonicals, sitemaps and redirects. Changing URLs is not automatically beneficial, so any restructuring should be planned carefully to protect existing visibility and links.

Internal linking

Internal links help crawlers discover pages and help distribute authority and context throughout a site. An audit identifies important pages with few or no internal links, excessive links to low-value URLs, broken links and links using inconsistent or unhelpful destinations.

It can also assess whether anchor text gives a useful indication of the linked page’s subject, whether navigation supports the intended page hierarchy and whether key commercial or informational pages are easy to reach. Internal linking is both a technical and structural consideration: a page may be technically valid but still underperform if the rest of the site rarely links to it.

Canonicalisation and duplicate content

Canonical signals help indicate which version of substantially similar pages should be treated as the main version. An audit checks that canonical tags exist where appropriate, use valid absolute or relative URLs consistently, and point to indexable pages that match the page’s purpose.

It also looks for conflicting signals, such as a page declaring one canonical URL while the sitemap, internal links or redirects favour another. Duplicate content can result from product variations, printer-friendly pages, URL parameters, syndicated text, location pages or multiple versions of the same page. The correct solution may be canonicalisation, redirection, consolidation, controlled indexing or simply improving the distinct value of each page.

Mobile usability and responsive behaviour

A technical SEO audit checks whether the website works reliably on mobile devices and whether search engines receive the same important content and signals across device types. It reviews responsive layouts, viewport configuration, text readability, interactive elements, navigation, intrusive overlays and content that is hidden or difficult to use on smaller screens.

Mobile checks should cover real page templates rather than only the homepage. Problems often occur on product listings, forms, tables, account areas or pages containing complex components. A page can pass a basic mobile check while still providing a poor experience because of horizontal scrolling, blocked controls or content that loads inconsistently.

Page speed and Core Web Vitals

Performance testing examines how quickly pages load and become usable, how stable the layout remains while content loads, and how promptly the page responds to interaction. The review may include server response time, caching, compression, image delivery, font loading, JavaScript execution, render-blocking resources and third-party scripts.

Results should be interpreted by template and page type because a single homepage test does not represent the entire website. Field data, where available, shows how pages perform for real users over time, while laboratory tests are useful for controlled diagnosis. The audit should connect each performance finding to a likely cause and a practical remedy rather than treating a single speed score as the objective.

JavaScript rendering

Where content or links depend on JavaScript, the audit checks whether search engines can render and interpret the page correctly. It compares the initial HTML with the rendered document to identify important text, links, metadata or structured data that is missing until scripts run.

Common issues include navigation links that are not available as standard crawlable links, content loaded only after user interaction, client-side redirects, incomplete server-side rendering and applications that return an empty shell to crawlers. JavaScript is not inherently a problem, but essential content should not depend on unreliable or unnecessarily complex execution.

Metadata and search appearance

Technical audits usually check title elements, meta descriptions, indexing directives, canonical tags, language attributes and other head-section elements. They identify missing, duplicated or excessively long titles, descriptions that do not reflect the page, and templates that apply the same metadata to unrelated URLs.

Metadata is not a complete content audit, but technical problems can prevent search engines from receiving the intended information. The review should also confirm that important pages have a single clear title, that headings are used logically, and that templates do not create misleading or duplicated page signals.

Structured data

Structured data gives search engines machine-readable information about entities and page types, such as products, organisations, articles, events or frequently asked questions. An audit checks whether the markup is present on the appropriate pages, uses properties that match the visible content and follows the relevant technical requirements.

It also checks for invalid syntax, missing required properties, conflicting entity information and structured data copied across pages where it does not apply. Markup can support enhanced search results, but it does not guarantee them and should not be used to describe content that users cannot see.

XML sitemaps

An XML sitemap audit checks that sitemap files are accessible, correctly referenced and limited to preferred, indexable URLs. It looks for broken, redirected, blocked, duplicate or non-canonical entries, along with outdated last-modified dates and incomplete coverage of important page types.

Large websites may need separate sitemaps for different content types or sections. A sitemap should support discovery and validation; it should not be used to compensate for weak internal linking or to list every URL the site has ever generated.

HTTPS, security and access

The audit verifies that pages use HTTPS consistently and that redirects, canonical tags, internal links and sitemap entries do not send users or crawlers back to insecure versions. It may also identify mixed content, certificate problems, insecure resources, exposed staging areas and access restrictions that prevent crawling.

Security configuration is not solely an SEO concern, but compromised pages, malware warnings and unreliable availability can remove pages from search results or prevent users from accessing them. Security findings should therefore be escalated and resolved alongside technical SEO work.

International and multilingual signals

For websites serving more than one country or language, an audit checks language and regional targeting signals, including hreflang annotations where they are appropriate. It verifies that language versions reference one another correctly, use valid URLs and do not contain conflicting canonical instructions.

It can also identify automatic redirects based on a user’s location or browser language that prevent crawlers and users from reaching alternative versions. Each regional page should provide a genuinely suitable experience rather than being a lightly modified duplicate.

Images, video and other media

Media checks cover image file size, dimensions, formats, responsive delivery, lazy loading, alt text and the availability of important resources to crawlers. Oversized images can affect performance, while incorrectly implemented lazy loading can prevent images from being discovered or displayed reliably.

Alt text should describe the purpose of an image when it conveys information, while decorative images generally need no descriptive text. Media files should also return the correct response, use stable URLs and avoid being blocked when they are important to understanding the page.

What the audit does not establish on its own

A technical audit can reveal whether a page is accessible and eligible to compete, but it cannot by itself determine whether the page is the best result for a search, whether its content fully satisfies users or whether its backlink profile is appropriate. Those areas require content, market, user experience and off-page analysis.

Similarly, not every warning requires immediate action. Findings should be prioritised according to the pages affected, the severity of the issue, the likelihood of limiting crawling or indexing, and the effort required to resolve it. A blocked key landing page is usually more urgent than a minor metadata inconsistency on a low-value URL.

How to use the findings

After the audit, group issues by cause rather than treating every affected URL as a separate problem. A template error may affect thousands of pages and should be fixed at source, while an isolated broken link can be handled individually. Validate changes by recrawling the relevant areas, checking server responses and monitoring indexing and performance over time.

The most useful outcome is a prioritised technical SEO action plan: protect important pages from accidental blocking, make preferred URLs clear, improve discovery through architecture and internal links, remove unnecessary duplication, resolve rendering and performance barriers, and then recheck the site after implementation.