BuiltWith is a long-running web technology lookup service that fingerprints public websites to determine what stack they run on. Paste a domain into builtwith.com or click the browser extension on any page, and BuiltWith returns a categorized report of the CMS, JavaScript frameworks, analytics platforms, ad networks, payment processors, hosting providers, CDN, A/B testing tools, CRM integrations and hundreds of other technology families detected on the site. The signatures come from a continually updated crawl of 673 million domains and 113,000+ known technology fingerprints.
Developers use BuiltWith to audit migration feasibility, debug third-party script conflicts, or understand how a site they admire ships its frontend. Marketing and sales teams use it to build target lists of companies running a specific competitor tool, to enrich CRM records with technographic data, or to time outreach based on detected technology changes. Agencies and consultancies rely on it during due diligence and for competitive landscape reports.
The free web lookup covers basic detection; paid tiers unlock full historical technology timelines, spend estimates, lead export, CRM integrations (Salesforce, HubSpot) and bulk API access. The browser extension installs on Chrome, Firefox and Edge and is the most commonly used surface — a lightweight way to check any page's stack without leaving the tab you are already on.
