How to Do a Technical SEO Audit Without Paid Tools

A technical SEO audit finds the mechanical problems preventing your site from ranking. Broken links, slow pages, missing canonical tags, crawl errors — these issues silently cap your rankings no matter how good your content is.

Most audit guides assume you have Ahrefs ($229/month) or Semrush ($249/month). You don’t need them. Every critical technical SEO check can be done with free tools, and for indie sites, the free tools are often more accurate because they pull data directly from Google.

This guide walks through a complete technical SEO audit using only free tools. By the end, you’ll have a prioritized action list of everything wrong with your site.

Why Technical SEO Matters Before Content

You can publish 100 well-researched articles, but if Google can’t crawl your pages, mobile rendering is broken, and your site takes 6 seconds to load — none of it ranks. Technical SEO is the foundation that lets your content perform.

Think of it this way: content is the product, internal linking is the distribution, and technical SEO is the infrastructure. You need all three, but infrastructure comes first.

The Audit: 8 Areas to Check

1. Crawlability and Indexing

Tool: Google Search Console (free)

Start here. GSC tells you exactly what Google can and can’t see. As we covered in our Google Search Console guide, the “Pages” report in GSC is your starting point for crawl issues.

Check these reports:

Pages > Indexing:

• “Indexed” — pages Google has crawled and added to its index
• “Not indexed” — pages Google found but chose not to index
• “Crawled, currently not indexed” — Google visited but decided the page isn’t worth indexing (often a quality or thin-content signal)
• “Discovered, currently not indexed” — Google knows the URL exists but hasn’t crawled it yet (often a crawl budget issue)

What to fix:

• Pages marked “not indexed” that should be: check for noindex tags, thin content, or duplicate content
• Pages marked “discovered but not crawled”: improve internal linking to these pages
• Soft 404s: pages that return 200 but have little or no content — either add real content or return a proper 404

Sitemaps report:

• Submit your XML sitemap if you haven’t
• Check that the number of discovered URLs matches your actual page count
• If GSC reports fewer URLs than expected, your sitemap may have errors

2. Page Speed and Core Web Vitals

Tools: Google PageSpeed Insights (free), Chrome DevTools Lighthouse (free)

Page speed is a confirmed Google ranking factor. But the specific metrics that matter are Core Web Vitals — three metrics that measure real user experience:

Largest Contentful Paint (LCP) — How fast the main content loads. Target: under 2.5 seconds.

Interaction to Next Paint (INP) — How quickly the page responds to user input. Target: under 200 milliseconds. (INP replaced FID in March 2024.)

Cumulative Layout Shift (CLS) — How much the page layout shifts as it loads. Target: under 0.1.

How to audit:

Go to PageSpeed Insights, enter your URL, and review both Mobile and Desktop scores. The tool shows your Core Web Vitals pass/fail status based on real Chrome User Experience Report data.

Common fixes for indie sites:

• Compress images — Use WebP or AVIF instead of PNG/JPEG. Most frameworks support automatic conversion.
• Reduce JavaScript — Ship less JS. Astro islands, partial hydration, or static generation help enormously.
• Use a CDN — Cloudflare’s free tier caches your static assets globally.
• Eliminate render-blocking resources — Defer non-critical CSS and JS.
• Set proper cache headers — Static assets should have long-lived Cache-Control headers.

3. XML Sitemap and Robots.txt

Tools: Browser (free), Google Search Console (free)

Your XML sitemap is a roadmap for search engines. Your robots.txt tells them what to crawl and what to ignore.

Sitemap checklist:

• Sitemap exists at /sitemap.xml or /sitemap-index.xml
• All important pages are included
• No redirects, 404s, or canonicalized URLs in the sitemap
• Last modified dates are accurate (not all set to the same date)
• Sitemap is submitted in GSC

Robots.txt checklist:

• File exists at /robots.txt
• Doesn’t block important pages or directories
• References your sitemap URL
• Doesn’t block CSS or JS files that Google needs to render pages

Common mistake: blocking /assets/ or /static/ in robots.txt, which prevents Google from rendering your pages properly. Google needs access to CSS and JS to understand your layout.

4. Broken Links and Redirects

Tools: Free link checker (Screaming Frog free tier up to 500 URLs, or your own script)

Broken links waste crawl budget and create poor user experience. They also prevent link equity from flowing through your site.

Check for:

• 404 errors (broken internal links)
• 301/302 chains (multiple redirects in sequence — each redirect dilutes link equity slightly)
• Links to redirecting external URLs (update them to the final URL)
• Orphan pages (pages with no internal links pointing to them)

For sites under 500 URLs, Screaming Frog’s free tier is sufficient. For larger sites, you can write a simple Python script that crawls internal links and reports status codes — which is exactly what ZensInk’s open-source site audit tool does.

5. Canonical Tags

Tool: Browser “View Source” (free)

Canonical tags (<link rel="canonical">) tell search engines which version of a page is the primary one. Get this wrong and you’ll have duplicate content issues that split your ranking power.

Check every page for:

• A self-referencing canonical tag (each page should point to itself as canonical)
• Correct absolute URL (not relative — https://example.com/page/, not /page/)
• HTTPS (not HTTP)
• Trailing slash consistency (pick one convention and stick to it)
• No conflicting canonicals (don’t have both a canonical tag and a noindex on the same page)

Common problems:

• Paginated pages all canonicalizing to page 1 (use rel="prev" and rel="next" instead)
• HTTP and HTTPS versions both indexable (set up a 301 redirect from HTTP to HTTPS)
• www and non-www versions both live (pick one and redirect the other)
• Filtered/sorted URL variations all returning 200 with identical content (canonical to the base URL or use URL parameters in GSC)

6. Mobile-Friendliness

Tools: Google Mobile-Friendly Test (free, now part of GSC), Chrome DevTools device mode (free)

Google uses mobile-first indexing, meaning it crawls and indexes the mobile version of your site. If your mobile experience is broken, your rankings suffer regardless of how good your desktop site looks.

Check:

• Text is readable without zooming (font size at least 16px for body text)
• Tap targets are adequately sized (minimum 48x48 pixels)
• No horizontal scrolling (content fits within the viewport)
• Mobile layout doesn’t hide important content
• Page loads quickly on mobile connections (test with Chrome DevTools throttling at “Slow 4G”)

GSC’s “Mobile Usability” report flags specific issues Google has detected. Fix everything it reports.

7. Structured Data and Schema Markup

Tools: Google Rich Results Test (free), Schema.org Validator (free)

Structured data helps search engines understand your content and can earn you rich snippets — enhanced search results that increase click-through rates significantly.

Audit your structured data:

• Check if you have any schema markup at all (view source and look for application/ld+json)
• Validate existing markup using the Rich Results Test
• Identify opportunities: articles (Article schema), FAQs (FAQPage schema), products (Product schema), breadcrumbs (BreadcrumbList schema)

For indie sites, the highest-ROI schema types are:

• Article — Helps your content appear in Google News and Top Stories
• FAQPage — Can earn expandable FAQ rich snippets in search results
• BreadcrumbList — Shows navigation breadcrumbs in search results
• Organization — Helps with brand entity recognition

If you’re using Astro, adding schema is straightforward — include JSON-LD directly in your layout templates. For Next.js, the next/schema or manual JSON-LD approach works well.

8. HTTPS and Security

Tools: Browser (check for padlock), Security Headers checker (free online tools)

HTTPS is a confirmed ranking factor since 2014. But security goes beyond the padlock.

Check:

• All pages load over HTTPS (no mixed content warnings)
• HTTP redirects to HTTPS (301 redirect, not just a link)
• SSL certificate is valid and not expiring soon
• HSTS header is set (tells browsers to always use HTTPS)
• Security headers are configured (X-Content-Type-Options, X-Frame-Options, etc.)

For sites on Cloudflare Pages, most of this is handled automatically. For self-hosted sites, check your server configuration.

Turning Audit Findings Into a Prioritized Action List

After running all 8 checks, you’ll have a list of issues. Not all issues are equally important. Prioritize like this:

Critical (fix immediately):

• Pages blocked from indexing that should be indexed
• Broken internal links on high-traffic pages
• No XML sitemap or sitemap with errors
• Mobile usability errors flagged by GSC
• HTTP pages not redirecting to HTTPS

High priority (fix this week):

• Core Web Vitals failures (LCP over 4 seconds, CLS over 0.25)
• Missing canonical tags or incorrect canonicals
• Orphan pages (add internal links)
• Missing structured data on key pages

Medium priority (fix this month):

• Redirect chains (flatten them)
• Missing or incorrect robots.txt rules
• Security headers not configured
• Thin content pages flagged as soft 404s

Low priority (fix when convenient):

• External links pointing to redirected URLs
• Minor CLS issues (under 0.1 but above 0.05)
• Schema markup on less important pages

Tools Summary

Every check in this audit uses free tools:

Check	Tool	Cost
Crawlability	Google Search Console	Free
Page speed	PageSpeed Insights	Free
Sitemap	Browser + GSC	Free
Broken links	Screaming Frog (500 URLs) or ZensInk site_audit	Free
Canonical tags	Browser “View Source”	Free
Mobile-friendliness	GSC + Chrome DevTools	Free
Structured data	Rich Results Test	Free
Security	Browser + free header checkers	Free

For sites over 500 URLs, the ZensInk open-source toolkit extends the free tier with unlimited URL crawling, internal link analysis, and orphan page detection — all without API costs.

After the Audit: What’s Next

A technical audit fixes the infrastructure. Once your site is crawlable, fast, and free of errors, the ranking factors that actually move the needle are content quality and internal linking.

Run this audit quarterly. Sites accumulate technical debt over time — new pages that aren’t linked properly, images that aren’t optimized, plugins that add render-blocking scripts. A 30-minute audit every three months keeps your technical foundation solid.

The best part? None of this requires a paid subscription. Google gives you the data for free — you just need to know where to look and what to fix.