How Does BuiltWith Work?

How does BuiltWith work? It crawls public websites on a schedule, then matches what it finds in the page source, HTTP headers, loaded scripts and DNS records against a library of technology signatures. Each match becomes a technology entry with first and last detected dates, so a domain lookup shows both a current stack and a history of changes.

How does BuiltWith work, step by step?

1. Crawl. BuiltWith fetches the public pages of a domain the way a browser would, on a recurring schedule. It does not log in, so anything behind authentication is out of scope. BuiltWith publishes its own crawl size and coverage figures; treat them as vendor claims until you have checked a sample of domains you know.
2. Fingerprint. The fetched page is compared against signatures: a script path only Google Tag Manager uses, a cookie name set by one analytics vendor, a header a CDN adds, a meta tag a CMS writes, a nameserver or MX record that points at a hosting or email provider. A match is a detection.
3. Keep history. Detections are stored with first and last seen dates. That is how BuiltWith can report that a site added a tool one month and dropped another later, and it is the basis of its technology usage trend reports.
4. Look up a domain. The simplest use is the domain lookup: type a website and read the grouped report, from analytics and advertising through to hosting and frameworks. The browser extension does the same for the page you are on.
5. Build a list. The lists product lets you pick a technology, add filters such as country, traffic tier or vertical, and export the matching domains. This is the sales and lead generation use, and the one most people pay for.
6. Query the API. The domain API returns the same detections as JSON for one domain at a time, and the lists API returns domains for a technology. Pricing and rate limits are on BuiltWith’s own site and change, so check there rather than here.

The method sets the limits. BuiltWith only sees what a public page exposes to a visitor. It cannot see the languages a backend is written in, the warehouse behind the dashboards, the internal tools engineers use, or the applicant tracking system unless the careers page loads it. It also reports a technology for as long as its fingerprint stays in the page, so an abandoned tag can linger as a detection. For a buyer that means BuiltWith is strong on the front-end, marketing and hosting layers and weak on everything that runs behind the load balancer. The technographics page explains which layers each detection method covers, and BuiltWith alternatives compares the tools side by side.

Where JobsPipe fits

JobsPipe is a jobs data API. It collects live postings from LinkedIn, Indeed, Y Combinator, Naukri, Workday, Greenhouse, Workable, SmartRecruiters, Ashby, Lever and Paylocity, returns them as one schema with closure tracking and a ghost score, and includes a free tier of 1,000 jobs a month at jobspipe.dev. Job postings fill BuiltWith’s gap: an engineering posting names the languages, databases, cloud and data tools a team actually runs, whether or not any of them touch the public site. Scan a domain with POST /v1/stack/scan or the free stack scanner, then confirm the backend with a posting search:

curl -X POST https://api.jobspipe.dev/v1/jobs/search \
  -H "Authorization: Bearer $JOBSPIPE_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{ "company_name_or": ["Shopify"], "status": "active", "limit": 25 }'

Every record carries technology_slugs, so the stack falls out of the results without a second tool.