A free, local-first alternative to BuiltWith
Market-research-oriented technology lookup — strong on technographic reports and lead lists, weaker on per-developer page detail.
Founded 2007 · Pricing: Free single-domain lookup via the web (limited); paid tiers for API access, bulk lookup, historical technology data and lead generation.
Overview
BuiltWith is the other name developers reach for when they think 'what's this site built with?'. It's slightly older than Wappalyzer as a commercial product, has always been proprietary, and has always been more of a sales-intelligence tool than a developer utility. That matters for how you should think about it. Where Wappalyzer started as an open-source extension and bolted a SaaS business on top, BuiltWith started as a SaaS and added a free extension afterwards to drive traffic to the site. Its strongest features — historical technology-usage timelines for a domain, lead lists of 'all SaaS companies running X', contact enrichment, spend estimation — are aimed at B2B sales teams, not frontend engineers. The free web-based lookup gets you a technology list plus a wall of 'upgrade for more' banners, which is honest marketing but also a constant reminder that the best of BuiltWith lives behind the paywall.
History
BuiltWith was founded in 2007 by Gary Brewer and has remained independent and profitable as a paid SaaS throughout. Its data grew primarily through web crawling — BuiltWith runs its own crawl infrastructure and accumulates historical snapshots of what technologies a domain used over time, which is the feature its sales-team customers most value. The product caters heavily to CRM integrations (HubSpot, Salesforce, Zoho) and has shipped lead-generation features that target ideal-customer profiles via installed technology combinations.
Who uses it and for what
A typical BuiltWith customer is a sales development rep or marketing ops engineer who needs to build a list like 'every Shopify Plus store in the US with more than 100 employees that also runs Klaviyo'. They pay for the Pro or Enterprise tier, run the query, export to CSV, sync to their CRM, and kick off a campaign. A secondary use case is competitive intelligence: watching what technologies a given domain adds or drops over time. BuiltWith's historical timelines ('switched from React to Vue in March 2024, added Segment in June') are a genuine differentiator there. Developers occasionally use the free lookup for one-off 'what's this site built on' curiosity, but they're not the target customer and the experience shows it.
Pricing in detail
What BuiltWith does well
Historical technology timelines
For any domain BuiltWith has crawled, you can see a timeline of when technologies were added, replaced or removed. This is unique among mainstream technology detectors and is genuinely useful for competitive intelligence.
Large domain database
BuiltWith's crawl coverage spans tens of millions of domains. If you need a list-based query — 'every site using technology X' — you can get an answer here that a browser extension simply cannot.
Sales-team integration
Native integrations with HubSpot, Salesforce and Zoho mean a RevOps team can wire BuiltWith into its CRM and have technographic fields populated automatically on every account.
Company-level metadata
Each domain lookup includes estimated spend, company size signals, location and sometimes contact information — data sales teams buy BuiltWith for specifically.
Where BuiltWith falls short
These are the gaps a developer-first, sourcemap-aware workflow cares about.
Shallow per-page output
The actual technology detection per page is less deep than Wappalyzer's. You get broad categories, limited version detail, and a lot of duplicated entries when a site uses common analytics stacks. If your question is 'what exactly is running on this page?', BuiltWith is not the tool.
No sourcemap awareness
The 'JavaScript Libraries' section is driven by script-src URL regex. Anything bundled inside webpack output stays invisible — which on a modern SPA is most of the libraries actually running.
No WordPress plugin enumeration by slug
WordPress plugins get partial coverage through specific rules. Unknown plugins under `/wp-content/plugins/<slug>/` do not get enumerated generically the way Sourcemap Explorer does it.
Paywall-heavy
Nearly every feature past a single-domain categorical view is paid. The free lookup is deliberately thin to push you to upgrade. Fine for BuiltWith's business, annoying if you want depth on one site.
Crawl-only, no local workflow
BuiltWith analyzes domains server-side by crawling them. It cannot look at your staging site, your internal admin, your preview deployment, or any authenticated route. Developers who need to study apps they actually work inside of get no value here.
Closed data, opaque methodology
Unlike Wappalyzer (originally open-source) or Sourcemap Explorer (based on a vendored open fingerprint set), BuiltWith's rules are fully proprietary. You cannot audit them, cannot extend them, cannot correct a false positive.
Where Sourcemap Explorer wins
Not across the board — we don't run bulk API queries and we don't publish market-share dashboards. These are the things we do that BuiltWithdoesn't.
Per-page depth instead of domain breadth
Sourcemap Explorer goes deep on the page you're on: bundled JavaScript libraries, exact versions from embedded `package.json`, WordPress plugins by slug, React/Vue/Svelte internals. BuiltWith goes wide across domains. Different jobs; we don't try to be BuiltWith.
Works on authenticated and internal sites
Because Sourcemap Explorer runs in your browser on whatever page you're viewing, it works on staging environments, internal admin tools, logged-in dashboards, preview deployments and localhost. BuiltWith's crawler cannot reach any of those.
Exact versions from sourcemap package.json
BuiltWith typically reports a library name with no version. Sourcemap Explorer reads embedded `package.json` files in sourcemaps and returns the precise semver.
Free, forever
BuiltWith starts in the hundreds-of-dollars-per-month range for anything beyond a single-domain lookup. Sourcemap Explorer is free with no paid tier to upgrade to.
No account, no quotas
No sign-up, no email required, no lookup credits to rate-limit. Browse as much as you want; every page is analyzed on-device.
A concrete workflow example
You're evaluating a potential competitor's frontend. BuiltWith tells you they use 'React, Webpack, jQuery, Google Analytics, HubSpot' and has a nice timeline showing they added Segment eight months ago. That's a useful CRM-feeder view. Sourcemap Explorer tells you the site is on Next.js 14.2.3 with App Router, React 18.2.0, TailwindCSS 3.4.1, Prisma 5.10.0, NextAuth.js 4.24.0, hosted on Vercel with Cloudflare in front. Both are true; they answer different questions.
Which one should you use?
Migration notes
Sourcemap Explorer doesn't replace BuiltWith's sales workflow. If you're using BuiltWith for technographic lead lists, keep BuiltWith. If you're using it as a developer substitute for 'what's this site built with?', Sourcemap Explorer gives a deeper, free answer on the page in front of you.
FAQ
Does Sourcemap Explorer give me BuiltWith-style lead lists?
No. We don't crawl the web or keep a domain database. If you need 'every site running Next.js in the US', that's a server-side sales product — BuiltWith, SimilarTech or the Wappalyzer API are the reasonable options. Sourcemap Explorer is a per-page developer tool for sites you're actively browsing.
Can it analyze sites behind login?
Yes. The extension uses your browser's existing session, so it sees exactly what your browser sees — authenticated apps, staging environments, internal tools, localhost. BuiltWith's crawler cannot reach any of those.
Is the BuiltWith data more accurate than the Wappalyzer fork you vendor?
For per-page technology detection, not especially — both are regex-driven and struggle with the same modern-SPA blind spots (bundled libraries, no exact versions). Where BuiltWith shines is the historical and aggregate layer, which is a different product category.
What about BuiltWith's 'relationships' / 'similar sites' features?
Those are domain-graph features built on top of BuiltWith's crawl database. Sourcemap Explorer doesn't have a domain graph — we look at the single page you're on and the sourcemaps it loads.
Other alternatives to compare
Try Sourcemap Explorer on the next site you study.
Install the extension, browse normally. When a site exposes sourcemaps, the toolbar icon turns green — click it and you'll see the full project tree plus the detected stack, with exact versions.