A free, local-first alternative to WhatRuns

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, customer staging environments, or any URL that contains tokens, IDs or other context you would not paste into a third-party search box. The free price tag is real, but it is not free in the sense that Sourcemap Explorer is free: WhatRuns sees what you look at, and the speed of the popup depends on a round-trip to a server you do not control. None of that is hidden from users — it is in the privacy policy — but it is rarely top-of-mind when you install a 'free Chrome extension that tells you what a site uses'.

The second thing to understand about WhatRuns is the underlying detection model. Because the work happens on the backend, the extension never reads the page assets in any sophisticated way. There is no JavaScript runtime introspection, no source-map parsing, no bundle inspection. The server applies a fingerprint set (header patterns, script-src regexes, cookie names, simple URL rules) against what the extension reports back, and returns a categorized list of likely technologies. That works well for the obvious surface — server, CMS, analytics tag — and breaks down for anything bundled. WhatRuns will tell you a site uses 'React'; it will not tell you it is React 18.2.0. It will tell you a site uses 'WordPress'; it will not enumerate the plugins by folder slug. The result is a tool that is pleasant to use and consistently returns the most basic answer, but rarely the most useful one for a developer who is trying to understand the page in front of them.

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.

Its evolution has been quieter than Wappalyzer's or BuiltWith's. There were no headline-making pivots, no acquisitions, no shifts to closed-source — the product looks broadly similar today to what it shipped in late 2017. The most visible change has been the steady professionalization of the alerts product (more granular notification rules, slightly more detection categories tied to alerts, an export-to-CSV path for marketing teams) without much investment in the depth of per-site detection. That product strategy makes sense for the audience WhatRuns serves — non-technical buyers who care more about a clean dashboard than per-version precision — but it means the gap between WhatRuns and developer-grade tools like Sourcemap Explorer has widened over time rather than narrowed. By 2026 the differentiator that 'WhatRuns has a nicer popup than Wappalyzer' has been mostly closed by Wappalyzer itself, and the underlying detection still cannot read sourcemaps.

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. They are not trying to ship code, they are not auditing a vendor's stack for procurement, they are not investigating a regression — they are scrolling and got curious. For that user the popup is fine: a categorized list of marketing-recognisable technologies (CMS, analytics, ad tech, font loader, video player), rendered in a few hundred milliseconds, with no learning curve. WhatRuns does that one job well.

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. That workflow is genuinely useful for sales reps watching prospect adoption, agency teams watching client setups, and product marketers watching category dynamics. WhatRuns is the only browser-extension product in the category that ships this as a first-class feature at a low price point. Developers, by contrast, are barely visible in the customer base. The product was not built for them, and a developer who installs WhatRuns hoping to see versions, plugins, internal libraries, or sourcemap-derived signals walks away disappointed within a few site visits.

Pricing in detail

What WhatRuns does well

Where WhatRuns falls short

These are the gaps a developer-first, sourcemap-aware workflow cares about.

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.

WhatRuns vs Sourcemap Explorer

Side-by-side on the dimensions a developer studying a single page actually cares about.

A concrete workflow example

You're a freelance consultant brought in to audit the marketing site of a mid-size SaaS company. The brief is to map their stack — frontend, analytics, marketing automation, payment — and recommend a few cleanup items before they launch a redesign. You start with WhatRuns because it is what you have installed, and the popup gives you a fast first read: Next.js, Vercel, Google Tag Manager, Segment, Intercom, HubSpot. That is genuinely useful, and it took ten seconds. But the brief asked you to recommend cleanup, and 'Next.js' on its own does not tell you whether the codebase is on the App Router or the Pages Router, whether they are still on Next 13 or already on 14 or 15, or whether the marketing pages and the dashboard share a build. WhatRuns cannot answer any of those questions, because it cannot see inside the bundle.

You switch to Sourcemap Explorer, refresh the page, and the popup now shows you Next.js 14.2.4 (with the App Router signature), React 18.2.0, Tailwind CSS 3.4.1, Framer Motion 11, the exact `@hookform/resolvers` and `zod` versions, plus the Vercel Analytics client library and a custom `@<customer>/ui` design-system package whose existence you would not have suspected from the marketing copy. Five minutes in, you have enough material to write a real audit. The two tools were not in competition for the first answer; they were in different leagues for the second.

Which one should you use?

FAQ

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