What is Technical SEO? The Complete Guide

Technical SEO is the process of making sure search engines can find, crawl, index, and understand your website. It covers everything that happens before a search engine even reads your content: the infrastructure that either allows or prevents your pages from ranking.

Without a solid technical foundation, even the best content and the strongest backlink profile will underperform. Google cannot rank pages it cannot crawl, and it will not rank pages it cannot index.

What does technical SEO cover?

Technical SEO is broad. It covers six core areas:

Crawlability: can search engine crawlers reach your pages? This includes your robots.txt configuration, internal link structure, crawl depth, and whether important pages are reachable from the homepage.

Indexability: once crawled, can your pages be indexed? Pages blocked by a noindex tag, canonical issues, or nofollow on all inbound links will be crawled but not indexed.

Site speed and Core Web Vitals: Google uses Core Web Vitals as a ranking signal. LCP (Largest Contentful Paint), INP (Interaction to Next Paint), and CLS (Cumulative Layout Shift) measure loading, interactivity, and visual stability.

HTTPS and security: all pages should be served over HTTPS. Mixed content (HTTP resources on HTTPS pages) causes browser warnings and can affect crawling.

Mobile usability: Google indexes the mobile version of your site first. Pages that are broken on mobile or significantly different from the desktop version create indexing problems.

Structured data: Schema.org markup helps search engines understand what a page is about and can unlock rich results in SERPs.

How is technical SEO different from on-page and off-page SEO?

The three pillars of SEO are:

• Technical SEO: can search engines access and understand your site?
• On-page SEO: is your content relevant, well-structured, and targeted at the right keywords?
• Off-page SEO: does your site have the authority and trust signals to rank competitively?

Technical SEO is the foundation. Fix technical issues first. Producing content on a site with crawling or indexing problems is wasteful, and the content may never be indexed at all.

What are the most common technical SEO issues?

Broken pages (4xx errors)

Pages returning 404 or 410 errors waste crawl budget and lose any link equity pointing to them. They also create a poor user experience. A site crawl will surface all broken pages and the internal links that point to them.

Redirect chains

A redirect chain occurs when Page A redirects to Page B, which redirects to Page C. Each hop slows page load and dilutes link equity. Google will follow chains but stops after a certain number of hops. See how to find and fix redirect chains.

Non-indexable pages

Pages can be non-indexable for several reasons: a noindex meta tag, a canonical tag pointing to a different URL, or being blocked in robots.txt. Non-indexable pages will not appear in search results, which is sometimes intentional (thank-you pages, admin areas) and sometimes a mistake.

Missing or duplicate titles and meta descriptions

Title tags and meta descriptions are among the most basic on-page signals. Missing ones are a missed opportunity. Duplicates confuse search engines about which page is canonical for a given topic.

Slow page speed

Core Web Vitals scores affect rankings directly. LCP measures how long it takes for the largest content element to load. Pages with an LCP above 4 seconds are flagged as poor. Unoptimised images are the most common cause.

Missing HTTPS or mixed content

If any page serves resources (images, scripts, stylesheets) over HTTP while the page itself is HTTPS, browsers display security warnings. Crawly's security headers audit surfaces mixed content alongside missing HSTS, CSP, and other headers.

Hreflang errors

Sites targeting multiple languages or regions use hreflang tags to tell Google which version of a page to serve in which locale. Missing x-default tags, incorrect language codes, and broken reciprocal links are all common issues. See the hreflang guide.

How do you audit technical SEO?

A technical SEO audit starts with a site crawl. Crawling your site gives you a complete picture of every URL, its status code, its on-page metadata, and its indexability, all at once.

The steps:

1. Crawl the site: use a desktop crawler to visit every URL and collect data
2. Review the issues dashboard: group problems by severity and type
3. Fix crawlability issues first: broken pages, redirect chains, robots.txt blocks
4. Fix indexability issues: noindex on pages that should rank, canonical mismatches
5. Review on-page signals: missing titles, duplicate H1s, missing meta descriptions
6. Check Core Web Vitals: use Google Search Console's Core Web Vitals report
7. Check structured data: validate schema markup with Google's Rich Results Test
8. Re-crawl after fixes: use crawl comparison to verify changes and catch regressions

Crawly runs this entire process for free, with no page cap. It groups issues by severity automatically and lets you diff any two crawls to see what changed.

How often should you run a technical SEO audit?

• Monthly for most sites: catches issues before they compound
• After any significant deploy: a new CMS, URL restructure, or site rebuild should always be followed by a crawl
• After a ranking drop: a technical audit is the fastest way to rule out site-side causes

For a full walkthrough of the audit process using Crawly, see the technical SEO audit guide.

Technical SEO checklist

A quick reference for the most important checks:

• robots.txt is accessible and not blocking important pages
• XML sitemap exists and contains only indexable URLs
• All pages are served over HTTPS with no mixed content
• No important pages are blocked by noindex
• No canonical tags pointing to wrong URLs
• No redirect chains longer than one hop
• No broken internal links
• Title tags present and unique on every page
• H1 present on every page
• Meta descriptions present and unique
• Core Web Vitals scores passing in Search Console
• Structured data valid and implemented on key page types
• Hreflang implemented correctly on international pages
• AI crawlers allowed in robots.txt (GPTBot, ClaudeBot, PerplexityBot)

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Technical SEO creates the conditions for everything else to work. No amount of content or links will compensate for a site that search engines cannot crawl and index properly.

Download Crawly to run a free technical SEO audit with no page cap.