Technical SEO Checklist for Developers: 9 Things I Check on Every Client Site

Most sites I audit look fine in the browser and fail silently in the crawler. Here's the checklist I run on every client site before touching a single line of content. Each item is a pass/fail you can verify in minutes.

1. Page speed on a real mobile connection

Run PageSpeed Insights on the homepage and the two most important conversion pages. Watch LCP, INP, and CLS — Google's Core Web Vitals — not just the aggregate score. A 90+ desktop score with a 45 on mobile is a fail.

2. HTTPS with no mixed content

curl -I https://example.com should return a 200 with HSTS headers. Then check for mixed-content warnings: one insecure script tag silently kills the trust signal the whole page is trying to build.

3. robots.txt isn't accidentally blocking everything

curl https://example.com/robots.txt

I've seen Disallow: / left over from staging on live sites. It takes ten seconds to check and weeks of lost indexing to discover otherwise.

4. Indexation coverage in Search Console

Open Google Search Console → Pages. Sort by "Not indexed." Pages that should be indexed but aren't are a structural problem, not a content problem — crawl budget, orphan pages, or duplicate signals.

5. XML sitemap exists and is submitted

A sitemap doesn't guarantee indexing, but a missing or stale one tells Google you don't maintain the site. Generate it, submit it in Search Console, and make sure it only contains URLs you actually want indexed (no 404s, no noindex pages).

6. Canonical tags on paginated and filtered pages

Every faceted/filtered URL and every paginated archive needs a canonical tag pointing at the right version. Without them, crawl budget bleeds into duplicate variants of the same page.

7. Structured data validates

Add schema.org markup for what the page actually is (Organization, LocalBusiness, FAQPage, Article) and test it with Google's Rich Results Test. Invalid schema is worse than no schema — it tells Google the markup can't be trusted.

8. Plugin and script audit

On WordPress sites: list every installed plugin and ask what each one does. The typical client site has 20+ plugins and uses 8. Each unused plugin is dead weight on every page load — and a security surface. Same rule for third-party scripts: if the analytics tag, chat widget, or font loader isn't pulling its weight, cut it.

9. One H1 per page, semantic HTML

Crawl any page and check the heading structure. Multiple H1s and div-soup layouts are still everywhere. It's a small thing, but it tells Google what the page is about — and it's free to fix.

Why this order

None of these items are content. That's the point. Content earns attention; the technical layer decides whether that content ever gets seen. If your site loads slowly, isn't crawled properly, or has a broken structure, it won't rank — no matter how good the writing is.

The full non-developer explanation of this layer — what it is, why traffic-without-leads is usually a technical problem — is here: Technical SEO Explained: Why Your Site Isn't Getting Leads.

Further reading: Google's Web Vitals documentation, and Portent's site-speed research on how load time affects conversion rates.