Oct 10, 2026 by Anthony York (YorkSoft Ltd)
Last Updated: October 10, 2026
A technical SEO checklist is your foundation for ensuring search engines can crawl, index, and rank your custom-coded website effectively.
Custom-coded websites give you complete control. That flexibility is powerful, but it also means you're responsible for getting the fundamentals right.
The stakes are real. That's systematic attention to the things search engines actually care about.
This guide walks you through a practical technical SEO checklist for custom coded websites, covering everything from crawlability to Core Web Vitals, with actionable steps you can implement immediately.
Search engines begin with crawling, sending automated bots to discover and read your pages. Custom-coded sites often stumble here because developers focus on user experience first and forget to signal to search engines how your site is structured.
Crawlability issues compound quickly. A blocked resource, a misconfigured robots.txt, or incorrect canonical tags can prevent entire sections of your site from being indexed. The result: pages exist, but Google doesn't know about them.
Your XML sitemap is a roadmap for search engines. For custom-coded websites, you must generate this dynamically or maintain it manually, there's no automatic plugin doing it for you.
Check your sitemap now:
/sitemap.xml?Your robots.txt file controls what crawlers can access. A poorly configured robots.txt can accidentally block entire directories from being crawled. Common mistakes include blocking CSS or JavaScript files (which modern search engines need to render your site properly) or accidentally blocking important content directories.
Test your robots.txt using Google Search Console. Verify that:
/css/, /js/, or /images/ directoriesIndividual pages need their own instructions. The robots meta tag tells crawlers whether to index a specific page and whether to follow its links.
Common issues:
noindex on pages you actually want indexed (often happens during development and gets forgotten)nofollow on internal links, which fragments your site's authorityCanonical URLs are equally critical. A canonical tag tells search engines which version of a page is the "official" one. Without it, search engines may treat similar pages as duplicates and split your ranking power across them.
For custom-coded sites, ensure:
Core Web Vitals measure user experience through three specific metrics: Largest Contentful Paint (LCP), Interaction to Next Paint (INP), and Cumulative Layout Shift (CLS).
Custom-coded websites often perform worse on Core Web Vitals than template-based platforms because developers must optimise every asset manually. There's no built-in image compression, lazy loading, or code splitting, you build it yourself or it doesn't happen.
Start by measuring. Use Google PageSpeed Insights, which pulls real-world data from the Chrome User Experience Report. This shows you actual performance on real devices, not just lab conditions.
Look for the "Good" threshold: LCP under 2.5 seconds, INP under 200 milliseconds, CLS under 0.1 (Understanding Core Web Vitals and Google search results | Google Search Central |...). Pages below these thresholds rank better and convert better.
For custom-coded sites, the biggest speed wins come from:
srcset to serve appropriately-sized versions for each device.defer or async attributes. Separate critical rendering path code from the rest.LCP measures when the largest visible content element loads. For most pages, that's a hero image or heading.
Optimise LCP by:
<link rel="preload">INP measures responsiveness, how long it takes your page to respond when users interact with it (clicking buttons, typing in forms, scrolling). High INP means your page feels sluggish.
Custom-coded sites often have INP problems because JavaScript event handlers are poorly optimised. Common causes:
Improve INP by breaking long tasks into smaller chunks, deferring non-critical work, and auditing third-party scripts for performance impact.
Structured data tells search engines what your content means. A product page with schema markup shows Google the price, rating, and availability directly, information it can display in rich snippets.
For custom-coded websites, you must add schema manually. There's no plugin to do it for you.
Implement schema for:
Use JSON-LD format, which is easiest to maintain in custom code. Validate your markup using Google's Rich Results Test before deploying.
A technical audit systematically identifies problems before they cost you traffic. For custom-coded websites, audits are especially valuable because you're not protected by platform defaults.
Start with the basics:
Custom-coded websites are prone to specific problems:
www, with session parameters) and forget to canonicalise them.Auditing tools save time by automating checks. For custom-coded sites, choose tools that give you raw data you can act on, not just scores.
Useful tools include:
Run audits regularly, monthly at minimum for active sites. Track trends over time. A single audit is a snapshot; repeated audits show whether your changes are working.
Modern websites rely on JavaScript to render content dynamically. Search engines have improved at rendering JavaScript, but inconsistencies remain. For custom-coded sites, this is a critical consideration.
Current guidance from sources like Semrush's technical SEO checklist for search engines and AI search emphasises that JavaScript rendering is now a standard part of technical SEO checklists.
View your page as Googlebot sees it:
If critical content loads via JavaScript, Google can usually render it, but there's a delay.
AI search systems like those discussed in DebugBear's 2026 technical SEO checklist are increasingly important. These systems have different requirements from traditional search engines.
Technical SEO shouldn't be an afterthought. Integrate it into your development workflow from the start.
Before launch:
After launch:
At YorkSoft Ltd, we help businesses across the UK, from Northampton-based repair centres to e-commerce operations, implement technical SEO that sticks. If you're building a bespoke web application or custom website and want to ensure the technical foundation is solid, contact YorkSoft Ltd for a technical SEO review.
The technical SEO checklist isn't a one-time task. It's an ongoing process. Sites that maintain technical excellence, fast load times, clean code, proper markup, consistently outrank competitors.
Getting the technical fundamentals right is non-negotiable for ranking. If your custom-coded website hasn't been audited for technical SEO in the past six months, you're likely leaving traffic on the table.
A comprehensive technical SEO checklist covers crawlability (robots.txt, XML sitemaps, canonical URLs), indexing (meta tags, noindex directives), Core Web Vitals (page speed, Largest Contentful Paint, Interaction to Next Paint), structured data markup, site architecture, security (HTTPS), mobile-friendliness, JavaScript rendering, and broken link detection. For custom-coded websites, you must also verify that your hand-written code doesn't inadvertently block crawlers or create rendering issues that affect indexing.
Start by checking Google Search Console to see which pages Google can crawl and index. Review your robots.txt and XML sitemap for accuracy. Test Core Web Vitals using PageSpeed Insights or Lighthouse. Verify structured data with the Schema.org validator. Check for broken internal links, redirect chains, and duplicate content. Examine your site's mobile responsiveness and HTTPS implementation. For custom code, manually inspect your HTML, CSS, and JavaScript to ensure no crawl barriers exist. Run automated audits using technical SEO tools, then prioritise issues by impact.
Use Google Search Console's URL Inspection tool to check individual pages. The Coverage report shows which pages Google has indexed and which it's blocked. Test your robots.txt file using the robots.txt tester in Search Console. Request indexing for key pages after fixing crawl issues. Check your XML sitemap submission status. For custom websites, verify that your code doesn't use JavaScript to hide critical content, as Google may struggle to render and index it. Monitor crawl statistics in Search Console to spot trends in blocked or excluded pages.
Core Web Vitals consist of three metrics: Largest Contentful Paint (LCP), First Input Delay (now Interaction to Next Paint or INP), and Cumulative Layout Shift (CLS). To improve LCP, optimise image sizes, defer non-critical JavaScript, and use a Content Delivery Network. Reduce INP by minimising JavaScript execution time and breaking up long tasks. Improve CLS by setting explicit dimensions for images and iframes, and avoiding layout-shifting animations. For custom-coded sites, audit your CSS and JavaScript for inefficiencies. Minify assets, enable compression, and lazy-load images below the fold. Test improvements using PageSpeed Insights or WebPageTest.
Yes. An XML sitemap helps Google discover and crawl all your pages, especially important for large or complex custom websites. Include all important pages, set priority and update frequency attributes, and submit it to Google Search Console. For hand-coded sites, ensure your sitemap generator or manual sitemap is accurate and updated whenever you add or remove pages. A well-maintained XML sitemap reduces crawl inefficiency and speeds up indexing of new content.
Run a full technical SEO audit at least quarterly, or whenever you make significant changes to your site's code, structure, or hosting. For custom-coded websites, conduct audits after deployments or updates that affect crawlability, performance, or indexing. Monitor key metrics (Core Web Vitals, crawl errors, indexation) in Google Search Console continuously. Use automated audit tools monthly to catch new issues early. If your site experiences a traffic drop, run an immediate audit to identify technical problems.
Google Search Console is essential and free; use it to monitor crawling, indexing, and Core Web Vitals. PageSpeed Insights and Lighthouse measure performance and user experience metrics. The W3C Markup Validator checks HTML validity. Screaming Frog SEO Spider crawls your site to find broken links, duplicate titles, and missing meta tags. Other providers offer technical audit features. For custom websites, these tools help identify issues in your hand-coded implementation. Start with free tools like Google Search Console and Lighthouse, then add paid platforms if you need deeper analysis.
