A free, local-first alternative to WhatRuns
Simple, free-first Chrome extension — lighter than Wappalyzer with a cleaner UI, but with the same detection blind spots and a backend-call-per-lookup architecture.
Founded 2017 · Pricing: Free Chrome extension; optional paid tier for 'technology change alerts' aimed at competitive-intel and marketing teams.
Overview
WhatRuns entered the browser-extension detector market in 2017 as a consumer-friendlier alternative to Wappalyzer. Its popup UI is visibly cleaner, its grouping feels more marketer-accessible, and it added a 'technology change alerts' feature that Wappalyzer didn't offer. It attracted a user base quickly — at one point it was one of the most-installed technology detection extensions in the Chrome Web Store — but the detection surface behind the nicer shell is narrower and, critically, backend-driven. When you click the WhatRuns popup on a page, the extension sends the page URL to WhatRuns servers and receives the technology list back from an API call. That architecture has privacy implications you should think about if you work on internal applications.
History
WhatRuns was founded in 2017 by Robin Singh as a lean, consumer-polished competitor to Wappalyzer. Its pitch was 'Wappalyzer for marketers' — less technical depth, a prettier popup, an easier 'alert me when this site adds X' product. It ran on a smaller fingerprint set than Wappalyzer and made up for that partly through curation (the fingerprints it did have were usually high-quality) and partly through the change-alerts layer that neither Wappalyzer nor BuiltWith offered at the same price point. The tool is still maintained and still popular as a lightweight daily-use extension.
Who uses it and for what
Most WhatRuns users open the popup occasionally when they hit a site they're curious about and want a quick read. The secondary audience is marketing and competitive-intelligence users who subscribe to the 'track technology changes' product and get email notifications when a competitor adds, drops or swaps a tool.
Pricing in detail
What WhatRuns does well
Clean, fast popup UI
WhatRuns's popup is the visual benchmark for the category. The grouping is intuitive, the hierarchy is scannable, and the visual weight is more marketer-friendly than Wappalyzer's more-developerish layout.
Curated fingerprint quality
Smaller database than Wappalyzer, but the rules that exist tend to be accurate. Fewer false positives on marketing-oriented technologies (CRM pixels, ad-tech, cookie banners).
Change alerts
The 'track this domain for technology changes' paid product genuinely fills a gap neither Wappalyzer nor BuiltWith's Basic tier serves directly. Useful for marketing teams watching competitors' stacks.
Free forever for the extension
Unlimited per-page lookups at no cost. The paywall only kicks in if you want the alerts product.
Where WhatRuns falls short
These are the gaps a developer-first, sourcemap-aware workflow cares about.
Backend-driven per lookup
Each invocation of the popup sends the URL of the page you're on to WhatRuns servers. For public pages that's unremarkable. For internal apps, authenticated dashboards, staging environments or anything you'd rather not have logged by a third party, it's a real problem. Sourcemap Explorer does not make any such call.
Smaller fingerprint database
Coverage is noticeably narrower than Wappalyzer's. Niche JavaScript libraries, less-common CMSes, newer frameworks often aren't in the database. You'll see more 'not detected' on specialty sites.
No sourcemap reading
Same blind spot as Wappalyzer and BuiltWith: anything bundled inside a webpack output is invisible. No exact versions from `package.json`, no ad-hoc package discovery.
No WordPress plugin enumeration
Plugin detection relies on the few rules that exist. Unknown plugins under `/wp-content/plugins/<slug>/` don't get enumerated.
Closed-source, company-controlled data
You depend on WhatRuns to add new fingerprints on their schedule; you cannot self-extend or audit.
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 WhatRunsdoesn't.
100% local analysis
Sourcemap Explorer does not send the URLs you visit to any backend. Every detection runs in-browser against the page's own assets. WhatRuns makes a backend call for every popup invocation.
Broader detection surface
Vendored Wappalyzer-derived fingerprint database (thousands of techs) plus sourcemap-derived signals finds libraries WhatRuns simply doesn't have a rule for, and extracts versions WhatRuns cannot.
Per-version exact detail
Where WhatRuns shows 'React', Sourcemap Explorer shows 'React 18.2.0' when the map includes `node_modules/react/package.json`.
Works on private / authenticated sites
No backend means you can run Sourcemap Explorer on your staging, your internal admin, your logged-in dashboard without exposing those URLs to a SaaS vendor.
A concrete workflow example
You're exploring a customer's private staging environment as part of a consulting engagement. WhatRuns's popup sends the staging URL to WhatRuns servers — a data-handling surprise you'd have to explain to your customer. Sourcemap Explorer runs entirely in-browser, reads the sourcemaps the staging site serves, and reports the stack without leaking the URL anywhere.
Which one should you use?
Migration notes
If your WhatRuns usage is purely the free extension for occasional casual curiosity, Sourcemap Explorer is a strict upgrade: broader database, local-only, sourcemap depth. If you rely on the paid technology-change-alerts product, that's a feature we don't offer — Sourcemap Explorer does not crawl and cannot notify you about changes on domains you don't visit.
FAQ
Is WhatRuns a tracker?
Not maliciously, but it is backend-driven: every popup invocation sends the URL you're on to WhatRuns servers. On public pages that's unremarkable; on internal apps it's a data-handling consideration. Sourcemap Explorer does not behave this way.
Does Sourcemap Explorer offer change tracking?
No. We persist per-site detection results locally, so you'll notice when you revisit a site and something changed, but we don't crawl and we don't email diffs. If change monitoring is core to your workflow, that's WhatRuns's paid tier.
Why is WhatRuns's database smaller than Wappalyzer's?
It's a younger project with a smaller maintainer team. The rules are curated rather than community-contributed, which gives it the cleaner-but-narrower profile.
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.