Technical SEO is the part of an SEO company’s work that deals with the website’s infrastructure rather than its words or links. The goal is narrow and concrete: make sure search engines can find every page that should rank, read it correctly, and render it without errors. A page that cannot be crawled or indexed cannot rank at all, so this work sits underneath everything else an agency does. Below is the actual service set most SEO companies group under “technical SEO.”
Crawlability and indexation
The first job is making sure search engines can reach and store the right pages. An SEO company reviews the robots.txt file to confirm it is not accidentally blocking important sections, checks the XML sitemap so it lists current, indexable URLs and nothing broken, and audits which pages are actually in Google’s index versus which are missing or wrongly included. They look for orphaned pages that no internal link points to, pages excluded by noindex tags that should not be, and thin or duplicate pages that dilute the site. On large sites they may also study crawl behavior through server log files to see which pages Googlebot visits and how often, which exposes wasted crawl activity and pages the bot ignores.
Site architecture and URL structure
Technical SEO covers how the site is organized. An agency maps the hierarchy so that important pages sit close to the homepage and follow logical, predictable paths. They review URL structure for clean, readable patterns and consistent formatting, and they check that the internal linking structure passes authority to priority pages. This is structural work: it is about the skeleton of the site, not the content written on each page.
Canonicalization, redirects, and duplicate content
Most sites generate the same content under several URLs through parameters, trailing slashes, or HTTP versus HTTPS. An SEO company sets canonical tags so search engines know which version to count, fixes redirect chains and loops, replaces temporary redirects with permanent ones where appropriate, and finds broken links that return errors. They also confirm the site runs fully on HTTPS. Handled poorly, these issues split ranking signals across duplicate URLs; handled well, they consolidate them.
Page experience and Core Web Vitals
Search engines measure how a page performs for real users. Technical SEO includes diagnosing Core Web Vitals, the metrics Google uses for loading, interactivity, and visual stability. An agency identifies what slows a page down, such as heavy images, render-blocking scripts, or unoptimized code, and recommends or implements fixes. They also confirm the site works correctly on mobile devices, since Google indexes the mobile version. The diagnostic and infrastructure side of speed is technical SEO; the broader topic of site speed strategy is its own subject.
Structured data implementation
Structured data, also called schema markup, is code that labels what a page is about so search engines can interpret it more precisely. An SEO company adds and validates this markup against Schema.org standards and checks it for errors. The deep strategy of which schema types to use is a separate question; here it is enough to know that adding and maintaining valid markup falls inside the technical service set.
Rendering and crawl errors
Modern sites built with heavy JavaScript can show content to users that search engines never see. Technical SEO includes checking how pages render for crawlers, confirming that key content and links appear in the rendered version, and resolving server errors, soft 404s, and other status-code problems flagged in tools like Google Search Console.
What to expect from this work
A technical SEO engagement usually starts with a full site audit that documents these issues, followed by a prioritized list of fixes ranked by impact. Some fixes the agency can implement directly; others require coordination with the client’s developers. Because sites change constantly, technical SEO is also ongoing monitoring, not a one-time project. When you ask an SEO company about technical services, expect them to describe a clear audit process, the tools they use, and how they hand off or implement fixes. Vague answers here are a warning sign, because this is the most measurable and verifiable part of SEO.