--- title: What Is This Website Built With? Free Tech Stack Checker url: https://sukeshdas.com/what-is-this-website-built-with/ description: Find out what any website is built with: CMS, WordPress plugins, AI builder, tracking tags, SEO score, AI crawlers, hosting and DNS. Free, private Chrome extension. --- [Home](https://sukeshdas.com/)[Blog](https://sukeshdas.com/blog/)[Tips & Tricks](https://sukeshdas.com/category/tips-tricks/) # How to Find Out What a Website Is Built With (Free Chrome Extension) By Sukesh Das October 4, 2026 11 min read ![Undersite Chrome extension showing what a website is built with and its SEO score](https://sukeshdas.com/wp-content/uploads/2026/10/undersite-demo-what-is-this-website-built-with-1024x576.webp) On this page 1. Why I built my own website checker 2. What Undersite replaces 3. How does Undersite detect a website’s tech stack? 4. Can Undersite detect CMS and plugin versions? 5. Which page builders can it detect? 6. How do I check if a site’s WordPress plugins are up to date? 7. How many posts, pages and custom post types does a site have? 8. How Undersite helps you quote a website redesign 9. Which tracking codes and pixels does Undersite find? 10. Can it tell me which fonts a website uses? 11. How do I find a website’s host and email provider? 12. What does the SEO check look at? 13. How do I check if a site is visible to ChatGPT and other AI search? 14. Can I export a report or scan automatically? 15. Is Undersite private and safe? 16. How do I use Undersite? 17. Website technology checker FAQs 18. Found problems on your own site? The fastest way to find out what a website is built with is a free Chrome extension called [Undersite](https://chromewebstore.google.com/detail/undersite-tech-stack-seo/lioocjedlfamcanhdkjlenppllnppodh). Open the site, click the icon, and in about two seconds you see the platform, page builder, WordPress plugins and whether they are outdated, 24 kinds of tracking codes, fonts, email provider, the real host behind Cloudflare, every published page, an SEO score and which AI crawlers can read the site. It is free, needs no account and sends nothing about you anywhere. ## Why I built my own website checker I’m Sukesh Das. I have built more than 1,200 websites since 2018, and almost every working day starts the same way: someone sends me a link. “Can you build something like this?” “Why is our site not on Google?” “Who even hosts this?” For years my answer meant a little ritual. One extension for the CMS, another to guess the WordPress theme, a third for pixels. A DNS website for the host, another for the email provider. A font inspector. An SEO extension. Then robots.txt and the sitemap opened by hand to count pages. Ten minutes and a dozen tabs, and some of those tools were quietly tracking my browsing or giving confident wrong answers. So I built one tool for myself that did all of it in Chrome’s side panel. I used it on real client work for weeks, fixed everything that annoyed me, and once the old ritual was completely gone I published it free for the community and my clients. This guide walks through every feature, using scans of my own site. ![Undersite Stack tab showing platform, theme, hosting and front end of a website](https://sukeshdas.com/wp-content/uploads/2026/10/undersite-demo-tech-stack-side-panel.webp) One click, one panel: Undersite scanning sukeshdas.com. ## What Undersite replaces | What I used to open | What Undersite shows instead | | --- | --- | | A CMS detector extension | Platform, theme or builder, host and front end in the first card | | A WordPress theme detector | Theme, child theme, plugins with versions and an update check | | A pixel or tag checker | 24 tracking and marketing platforms with copyable IDs | | A font inspector | Typography card with fonts and sizes | | DNS and hosting lookup sites | Host, origin server, DNS, email provider, raw records, sites on the same IP | | robots.txt and sitemap by hand | Every published URL grouped by post type, one click to copy | | An SEO extension | Score out of 100 with plain-language findings | | Nothing (no tool did this) | AI search visibility for 12 AI crawlers plus llms.txt | ## How does Undersite detect a website’s tech stack? Every platform leaves fingerprints: file paths like `/wp-content/`, JavaScript objects, class names, meta tags and server headers. Undersite matches those against around 180 technology signatures and shows a confidence bar and the evidence for each result. If a site hides something, it says “unknown” instead of guessing. The first card answers the four questions I always ask first: **platform** , **theme or builder** , **hosted on** and **front end** . Below it, results are grouped: - **27 CMS and site platforms** , including WordPress, Shopify, Squarespace, Wix, Webflow, Framer, Ghost, Drupal, Joomla, HubSpot CMS, Kajabi, Duda and Carrd. - **11 AI website builders** : Lovable, Bolt.new, v0, Durable, 10Web, Base44, Readdy, Hostinger Website Builder, Dorik, B12 and Gamma, with a clear “built with AI” note. - **9 e-commerce platforms** such as WooCommerce, Magento, BigCommerce, PrestaShop and Ecwid. - **16 frameworks and 10 libraries** , from React, Next.js, Vue, Astro and SvelteKit to jQuery, Tailwind and GSAP. - **10 chat and AI assistants** including Intercom, Tidio, Crisp, Tawk.to, Zendesk, Chatbase and Voiceflow. - Payments, security tools like reCAPTCHA and Cookiebot, CDNs and web servers. ## Can Undersite detect CMS and plugin versions? Yes, wherever the site makes the version public. Knowing the version tells you how old a site is and how much work an update or rebuild will take. Undersite reads versions for: - **CMS platforms:** WordPress core, Squarespace (7.0 or 7.1, and whether the site uses Fluid Engine), Drupal, Joomla, Ghost, Framer and Jimdo. - **WordPress themes and plugins:** the active theme and every plugin that loads files on the page, including Elementor, Kadence Blocks, Fluent Forms, WooCommerce and Easy Digital Downloads. - **Libraries:** jQuery and Bootstrap. Many sites hide their versions on purpose, mine included, as a security measure. When a version is not public, Undersite shows the technology without one rather than guessing. ## Which page builders can it detect? Elementor, Divi, Bricks, Beaver Builder, Oxygen, WPBakery, Kadence Blocks and the WordPress Block Editor. For me this answers the client’s real question, “will I be able to edit it myself?”, before the first call. ## How do I check if a site’s WordPress plugins are up to date? On any WordPress site, the WordPress details card lists the core version, the active theme and child theme, and the plugins loading on the page with their versions. Press **Check plugins for updates** and Undersite asks the official WordPress.org directory for the latest versions, then flags anything outdated in red. It also recognises Yoast, Rank Math, All in One SEO, SEOPress and The SEO Framework. Premium plugins and plugins that load nothing on the front end cannot be checked from outside, and Undersite tells you that honestly. ![Undersite WordPress details with theme and plugins, and sitemap content grouped by type](https://sukeshdas.com/wp-content/uploads/2026/10/undersite-demo-wordpress-plugins-sitemap.webp) WordPress details next to the site-wide content map. ## How many posts, pages and custom post types does a site have? The site-wide card answers this in one look. Undersite reads robots.txt and every sitemap file, counts the published URLs and groups them by type: posts, pages, products, categories and any custom post type. On my site it shows 30 posts, 28 portfolio items, 25 pages, 10 categories and 4 tools. - **One-click copy** for each post type, or every URL at once. Perfect for migrations, redirects and content audits. - **Quick links** to open the sitemap, open robots.txt, and run a Google index check (a site: search in a new tab, so Undersite itself never contacts Google). - **No sitemap? No problem.** If it is missing or broken, Undersite discovers pages from the site navigation instead. ## How Undersite helps you quote a website redesign This is the job I built it for. Before I can send a redesign quote I need to know how big the site is and what it runs on. I used to email the client a list of questions: how many pages, how many blog posts, do you have products, who is your host, which email do you use, which tracking do you need to keep? Half the time they did not know. Now I open their site and click once. Undersite gives me the platform and version, the page builder, the plugins, the exact count of pages, posts, products and custom post types, the host, the email provider and every tracking code that must survive the move. I can send an accurate quote the same day, without a single back-and-forth email, and export the scan as a PDF to attach to the proposal. ## Which tracking codes and pixels does Undersite find? This is where I used to need the most extensions. Undersite covers **24 tracking and marketing platforms** in one place, and shows each tracking ID with a copy button: | Type | Platforms | | --- | --- | | Analytics (13) | Google Analytics, Google Tag Manager, Meta Pixel, Microsoft Clarity, Hotjar, Mixpanel, Amplitude, PostHog, Segment, Matomo, Plausible, Fathom, Yandex Metrica | | Ads and pixels (7) | Google Ads, Microsoft Advertising UET, LinkedIn Insight Tag, TikTok Pixel, Pinterest Tag, Snap Pixel, X (Twitter) Pixel | | Marketing tools (4) | HubSpot, Klaviyo, Mailchimp, GoHighLevel | It is just as useful on your own site: you can check in seconds that your Tag Manager container and pixels are actually firing on the page. ## Can it tell me which fonts a website uses? Yes. The typography card lists the font family and size for H1, H2, H3, body text and buttons, and copies the full set with one click. It also detects Google Fonts and Adobe Fonts. ![Undersite tracking codes with copyable Google Tag Manager ID, and typography card with fonts and sizes](https://sukeshdas.com/wp-content/uploads/2026/10/undersite-ext-tracking-typography.webp) Tracking IDs and typography from my own site. ## How do I find a website’s host and email provider? The hosting card shows the host and how it was identified, the IP address, origin server, DNS provider and email provider, plus infrastructure like Cloudflare or LiteSpeed. All raw DNS records (A, AAAA, NS, MX, TXT, DMARC and SOA) have copy buttons. - **40+ hosts and DNS providers** , including Hostinger, SiteGround, Bluehost, GoDaddy, Namecheap, Kinsta, WP Engine, Cloudways, DigitalOcean, AWS, Vercel and Netlify. - **12 email platforms** : Google Workspace, Microsoft 365, Zoho Mail, Proton Mail, Fastmail, Titan Email, iCloud Mail, Yandex 360, Cloudflare Email Routing, Namecheap Private Email, Rackspace Email and Mailgun. - **The real host behind Cloudflare.** Most tools stop at “Cloudflare”. Undersite follows the site’s own mail server to the origin host where it can. - **Find sites on this IP.** One optional click lists other domains sharing the same server, a quick way to tell shared hosting from a dedicated machine. ![Undersite hosting and DNS card with origin server behind Cloudflare and raw DNS records](https://sukeshdas.com/wp-content/uploads/2026/10/undersite-demo-hosting-dns-checker.webp) My site is behind Cloudflare, and Undersite still finds the origin server and email host. Server details shown are sample values. ## What does the SEO check look at? The SEO tab scores the page out of 100, shows whether it can be indexed, and counts errors, warnings and notes. Every finding is explained in plain words, such as a meta description that Google will cut off, or headings that skip a level. | Section | What it checks | | --- | --- | | Meta | Title and length, meta description and length, canonical, robots meta, language, mobile viewport | | Content | Word count, H1 count and text, H2 and H3 counts, H1 versus title, images and missing alt text | | Technical | HTTPS, mixed content, charset, favicon, internal and external links | | Structured data and social | Schema types, Open Graph tags, Twitter Card, hreflang | ![Undersite SEO tab with an on-page SEO score of 100 and meta tag checks](https://sukeshdas.com/wp-content/uploads/2026/10/undersite-ext-seo-score-tab.webp) The SEO tab on my homepage. ![Undersite on-page SEO checks for meta tags, content, headings and structured data](https://sukeshdas.com/wp-content/uploads/2026/10/undersite-ext-on-page-seo-checks.webp) ## How do I check if a site is visible to ChatGPT and other AI search? No tool I used did this, so I built it in. The AI search visibility section reads robots.txt and shows whether 12 AI crawlers are allowed or blocked, each labelled with what it does: GPTBot (OpenAI training), OAI-SearchBot (ChatGPT search), ChatGPT-User (ChatGPT browsing), ClaudeBot, Claude-SearchBot, Google-Extended (Gemini), PerplexityBot, Applebot-Extended (Apple Intelligence), Meta-ExternalAgent, CCBot (Common Crawl), Bytespider and Amazonbot. It also tells you whether the site publishes an `llms.txt` file. When a client asks why AI tools never mention them, this section often gives the answer in seconds. My [GEO checklist](https://sukeshdas.com/squarespace-geo-checklist/) covers what to do next. ![Undersite AI search visibility showing 12 AI crawlers and llms.txt status](https://sukeshdas.com/wp-content/uploads/2026/10/undersite-ext-ai-search-visibility.webp) All 12 AI crawlers allowed and llms.txt published on my site. ## Can I export a report or scan automatically? Yes to both. **TXT** downloads the full scan as a text file and **PDF** opens a printable report you can save and attach to a proposal. Turn on **Allow scanning on every tab** and Undersite scans as you switch tabs, which is ideal for competitor research. The panel follows your light or dark system theme. ## Is Undersite private and safe? I built it with the rules I wanted from every other tool: - No account, no analytics, no tracking, no ads and no Undersite server. - It reads a tab only after you click its icon, unless you turn on auto-scan. - Analysis runs on your device. Only the scanned hostname goes to a public DNS resolver for the hosting lookup. - Results stay in session memory and disappear when Chrome closes. - The plugin update check and sites on this IP lookup are optional and ask permission the first time. - It never does things that help attackers, like listing WordPress usernames. Everything is spelled out in my [extensions privacy policy](/extensions-privacy/). ## How do I use Undersite? 1. Add [Undersite from the Chrome Web Store](https://chromewebstore.google.com/detail/undersite-tech-stack-seo/lioocjedlfamcanhdkjlenppllnppodh) and pin it to your toolbar. 2. Open any website and click the Undersite icon. The side panel opens and the scan starts. 3. Read the Stack tab, switch to SEO, and export a report if you want to keep it. ## Website technology checker FAQs ### How can I tell what a website is built with? Use a free extension like Undersite. Open the site, click the icon, and it shows the platform, page builder, plugins, frameworks, tracking codes, hosting and more in about two seconds. ### How do I check if a site’s WordPress plugins are outdated? Undersite lists the plugins loading on the page with their versions. Press Check plugins for updates and it compares them with WordPress.org and flags outdated ones in red. ### How many tracking platforms does Undersite detect? 24, including Google Analytics, Google Tag Manager, Meta Pixel, Microsoft Clarity, Hotjar, TikTok, LinkedIn and Pinterest tags, HubSpot and Klaviyo, each with a copyable tracking ID. ### Can I see how many pages and posts a website has? Yes. Undersite reads the sitemap and groups published URLs by post type, including custom post types, with one-click copy for each group. ### How do I find a website’s email provider? Undersite reads the domain’s MX records and recognises 12 email platforms, including Google Workspace, Microsoft 365, Zoho Mail and Proton Mail. ### How do I check if a site allows AI crawlers? Undersite reads robots.txt and shows whether 12 AI crawlers, including GPTBot, ClaudeBot and PerplexityBot, are allowed or blocked, and whether llms.txt exists. ### Can Undersite detect WordPress, plugin and Squarespace versions? Yes, when the site makes them public. It reads versions for WordPress core, themes and plugins, Squarespace 7.0 or 7.1 and Fluid Engine, Drupal, Joomla, Ghost, Framer, Jimdo, WooCommerce, Elementor, jQuery and Bootstrap. ### How can I quote a website redesign faster? Scan the site with Undersite. In one click you get the platform, builder, plugins, number of pages, posts and custom post types, host, email provider and tracking codes, so you can quote without asking the client a list of questions. ### Is Undersite free? Yes. It is free, needs no account and collects no data. ## Found problems on your own site? Run Undersite on your own website first. If it shows outdated plugins, missing tracking, SEO findings or blocked AI crawlers and you would rather not fix them yourself, that is the work I do every week. [Send me a short brief](https://sukeshdas.com/contact-us/#brief) and I will reply within one working day. You can also read [the story of how I built Undersite](/project/undersite-chrome-extension/). Related guides: [GEO checklist](https://sukeshdas.com/squarespace-geo-checklist/), [schema markup templates](https://sukeshdas.com/squarespace-schema-markup/) and [free floating WhatsApp button](https://sukeshdas.com/free-floating-whatsapp-button/). Related service [Chrome extensions](https://sukeshdas.com/services/chrome-extension-development/) Browser extensions for internal teams or public release, built on Manifest V3 and ready for the Chrome Web Store. [See the service](https://sukeshdas.com/services/chrome-extension-development/) [Case study: Undersite Chrome Extension](https://sukeshdas.com/project/undersite-chrome-extension/) Share this article - [AI search visibility](https://sukeshdas.com/tag/ai-search-visibility/) - [Chrome Extension](https://sukeshdas.com/tag/chrome-extension/) - [hosting checker](https://sukeshdas.com/tag/hosting-checker/) - [website technology checker](https://sukeshdas.com/tag/website-technology-checker/) - [what is this website built with](https://sukeshdas.com/tag/what-is-this-website-built-with/) - [WordPress theme detector](https://sukeshdas.com/tag/wordpress-theme-detector/) ![Sukesh Das](https://sukeshdas.com/wp-content/uploads/2026/09/profile-Sukesh-Das-150x150.webp) Written by Sukesh Das Web designer and developer with 1,200+ sites built. If this article describes your problem, I can fix it for you. [Ask me about your site](https://sukeshdas.com/contact-us/) ## Start the discussion [Cancel reply](/what-is-this-website-built-with/?format=md#respond) On this page 11 min read 1. Why I built my own website checker 2. What Undersite replaces 3. How does Undersite detect a website’s tech stack? 4. Can Undersite detect CMS and plugin versions? 5. Which page builders can it detect? 6. How do I check if a site’s WordPress plugins are up to date? 7. How many posts, pages and custom post types does a site have? 8. How Undersite helps you quote a website redesign 9. Which tracking codes and pixels does Undersite find? 10. Can it tell me which fonts a website uses? 11. How do I find a website’s host and email provider? 12. What does the SEO check look at? 13. How do I check if a site is visible to ChatGPT and other AI search? 14. Can I export a report or scan automatically? 15. Is Undersite private and safe? 16. How do I use Undersite? 17. Website technology checker FAQs 18. Found problems on your own site? Browse topics Tips & Tricks - [Tutorial4](https://sukeshdas.com/category/tutorial/) - [Wordpress2](https://sukeshdas.com/category/wordpress/) - [Website & Conversion9](https://sukeshdas.com/category/website-conversion/) - [Squarespace7](https://sukeshdas.com/category/squarespace/) - [Divi2](https://sukeshdas.com/category/tips-tricks/divi/) - [SEO & Local SEO2](https://sukeshdas.com/category/seo-local-seo/) - [Lead Generation2](https://sukeshdas.com/category/lead-generation/) - [Elementor1](https://sukeshdas.com/category/tips-tricks/elementor/) - [AI Search1](https://sukeshdas.com/category/ai-search/) - [All articles](https://sukeshdas.com/blog/) Want this handled for you? Send a short brief and get a fixed quote. [Get a free quote](https://sukeshdas.com/contact-us/) Keep reading ## More from the *blog.* [All articles](https://sukeshdas.com/blog/) Lead Generation Oct 3, 2026 ### [Floating WhatsApp Button: Free Chat Widget Code for Any Website (6 Platforms)](https://sukeshdas.com/free-floating-whatsapp-button/) Add a free floating WhatsApp button to any website with one copy-paste code: settings for number,… Squarespace Oct 3, 2026 ### [Squarespace vs WordPress for Therapists and Coaches: Honest Comparison](https://sukeshdas.com/squarespace-vs-wordpress-therapists-coaches/) Squarespace vs WordPress for therapists and coaches, from a designer who builds on both: 3-year costs,… Squarespace Oct 3, 2026 ### [Squarespace GEO Checklist: 10 Proven Steps to Stop Being Invisible to AI](https://sukeshdas.com/squarespace-geo-checklist/) A practical Squarespace GEO checklist: 10 checks with exact Squarespace menu paths, fixes and time estimates…