What is this website built with? How to check a site's CMS, builder and tools

By Morten Farstad Myrmel · Published 10 October 2026 · 10 min read

Whether a plumber's website runs on WordPress with Elementor, on a $16-a-month Wix plan, or on a GoHighLevel funnel tells you a lot before you ever talk to them: who built it, roughly what they paid, whether they can edit it themselves, and what you would be replacing. The same page source tells you whether they track anything, whether they take bookings online and which chat or review widget they pay for. Here is how to read it in a minute, a cheat sheet of the fingerprints we check for, and what to do when you have 500 sites instead of one.

The 60-second manual check

1. Open the site in a desktop browser. Press Ctrl+U (Windows) or Cmd+Option+U (Mac) to open the page source.
2. Press Ctrl+F and search for generator. Many platforms announce themselves in a tag like <meta name="generator" content="WordPress 6.6">. Squarespace, Wix, Webflow, Joomla, Drupal, HubSpot, Divi and Elementor all use it.
3. No generator tag? Search for the domains in the table below, in this order: wp-content, wixstatic, squarespace, website-files, wsimg, cdn-website, editmysite, leadconnectorhq. The first hit usually settles it.
4. Then search for gtag, gtm.js, fbevents and callrail for tracking, and housecallpro, servicetitan, getjobber and calendly for booking.

That is the whole method. Everything below is detail: what the fingerprints look like, what they mean, and where they lie to you.

Cheat sheet: CMS and website builder fingerprints

These are the signatures we look for ourselves. A fingerprint is a resource the page loads (a script, stylesheet or image URL) or a generator tag, never a product name mentioned in the text. A site that says “built with WordPress” in its footer may be lying; a site that loads /wp-content/themes/… is not.

Reading the table against real data: of the 180 home-service websites we read in our October 2026 test (roofers, plumbers and HVAC in three US metros), 59 loaded WordPress resources, 23 of those used Elementor, 10 were on Wix, 9 on Duda, 7 on GoDaddy's builder and 6 on Webflow. The rest were hand-built, on smaller platforms, unreachable, or gave no fingerprint on the pages we read.

Cheat sheet: analytics, ad tags and call tracking

These matter more than the builder if you sell SEO, ads or anything you have to prove works. A site with no tag at all cannot tell its owner where a single lead came from.

Cheat sheet: booking, forms, chat and reviews

A “Book now” button that opens the contact page is not online booking. Check where the link goes before you tell a prospect they have none.

Lookup tools, and what they are good for

If you would rather not read source, several tools do the lookup for you. We use them too; the honest summary is:

• BuiltWith has the broadest database and a long technology history per site. Single lookups are free; lists, exports and the API are paid, and the price is set for sales teams rather than freelancers.
• Wappalyzer is best known as a browser extension that shows the stack of the page you are on. Free for one site at a time; bulk lookups and lists are paid.
• WhatCMS answers the narrower question (“which CMS?”) quickly and is free with daily limits.
• WhatRuns is another extension, lighter than Wappalyzer, good enough for the builder and the main scripts.

All of them are better than the manual check for a single unfamiliar stack, and all of them report what their last crawl saw, which can be months old for a small local site. When the tool and the page source disagree, the page source wins.

Where fingerprints lie

• Not observed is not “not installed”. A Google Tag Manager container can load the Meta Pixel without fbevents.js ever appearing in the source. Record “no pixel seen in the source”, not “no pixel”.
• JavaScript-rendered sites (some Wix and most React single-page apps) show very little in the raw source. The builder fingerprint is usually still there; the content is not.
• Agency CDNs and proxies sometimes rewrite resource URLs to the site's own domain, hiding the platform. Look at cookie names and response headers in the browser's developer tools (Network tab) when the source is clean.
• The home page is not the whole site. Booking widgets and forms often live only on the contact or schedule page. Check at least those two.

Checking a whole list instead of one site

For a prospect list of 200 to 5,000 websites, nobody opens the source by hand. Your options, cheapest first:

1. A script. Fetch each home page (and the contact page, if you can find it), search the HTML for the fingerprints above, and write one row per site. A morning's work for a developer, plus the ongoing work of keeping the fingerprints current. Mind the rules: one request per page, respect robots.txt, and do not retry sites that block you.
2. Paid lookup lists from BuiltWith or Wappalyzer, filtered by technology and location. Good coverage of bigger sites; patchy for small local businesses that were last crawled months ago, and you still have to join the result to your own list.
3. Send us the list. Lead Notebook reads the home page plus up to three contact, services or booking pages per site and returns a spreadsheet with the builder, analytics and ad tags, call tracking, forms, booking and chat tools, plus emails, phones and advertised services, each with the page it was found on. Your own record IDs come back unchanged. Dead, parked and blocked sites are reported and never charged, and the first 20 websites are free.

Frequently asked questions

How can I tell if a website is built with WordPress?

Open the page source and search for wp-content or wp-includes. Those folders only exist on WordPress sites. Many WordPress sites also carry a meta generator tag that says WordPress, and the theme name appears in paths like /wp-content/themes/<theme-name>/.

What CMS is this website using if I can't find any fingerprint?

It may be hand-coded, built with a static site generator, or a builder that serves everything from the site's own domain. Check the response headers and cookie names in the browser's developer tools, and look for a login page such as /admin or /wp-admin. If nothing turns up, record it as unknown rather than guessing.

Is there a free tool that shows what a website is built with?

Yes. BuiltWith and Wappalyzer offer free single-site lookups and browser extensions, and WhatCMS and WhatRuns focus on the CMS and front-end stack. They are good for one site at a time; checking hundreds of sites or exporting lists is a paid feature on all of them.

Can I check what hundreds of websites are built with at once?

Not for free with the lookup tools, which limit bulk checks to paid plans. You can write a script that fetches each home page and searches for the fingerprints in this guide, or send the list to a service such as Lead Notebook, which reads each site and returns the builder, tracking, booking and chat tools with the page they were found on.

Fingerprints in this guide are the ones we check for ourselves as of October 2026; vendors change their CDN hostnames now and then, so verify against a site you know before you rely on one. Counts come from our own test of 180 Google Maps listings (roofers in Dallas, plumbers in Denver, HVAC contractors in Atlanta) and describe that sample only.