WhatRuns tells you what a site runs. TechSpy tells you what it means.
You already know how to read a tech-stack list. You searched for an alternative because the list stopped being enough — the SPA came back blank, there was no infra data, no API, nothing to actually act on.
That's the whole difference in one line:
- WhatRuns → a list of technologies. You interpret it.
- TechSpy → Verdict + Evidence + Implications, with High/Medium/Low confidence markers. The read is done for you.
No extension to install. Paste a domain — ideally one that came back thin in WhatRuns — and see the difference on a site you already checked.
Free — no card, 30 scans/day.
The SPA blind spot: where the extension goes quiet
Here's the honest technical reason WhatRuns thins out. It fingerprints the static HTML and JS the server hands over. On a client-rendered React or Next.js site, that first response is a near-empty shell — the real app boots in the browser afterward. So the extension reads what little is there and stops.
Those SPA sites are exactly the ones you most need answered — modern startups, product companies, anything built in the last five years.
TechSpy reads the layer the shell hides:
- JS-runtime fingerprints — what the app actually loads once it executes, not just the empty HTML
- HTTP headers — server, CDN, security, framework signals the markup never shows
- Deep Scan — a real headless render plus HAR capture that surfaces hidden APIs and SDKs firing after load
Same blank-looking site. Full runtime stack instead of two generic guesses.
A raw list vs a read you can act on
Even when detection works, a pile of chips still leaves the thinking to you. TechSpy does that part:
- Grouped by meaning — analytics, infra, payments, security, marketing — not one scrambled cloud
- Confidence markers — every finding tagged High / Medium / Low so you know what to trust
- Verdict / Evidence / Implications — a plain-English read of what the stack signals about the company
- Honest when blocked — if Cloudflare or a bot wall stops a scan, TechSpy says so. No faking a confident 100%.
That last point matters more than it sounds. Integrity over a fake-complete list is the difference between a tool you trust and a tool you double-check.
Beyond the tech stack: infra and operational signals
A stack list is one slice of the picture. The company's real posture lives in its infrastructure — and none of this is technology WhatRuns is built to report:
- DNS / DMARC / SPF / DKIM audit — email-auth and domain hygiene at a glance
- Subdomain discovery — catch
staging.,api.,careers.and infra expansion before it's announced - Sitemap structure — how the site is actually organized and what it's prioritizing
- Deep Scan — hidden APIs and SDKs pulled from a real headless render + HAR
- Interact — an LLM clicks and fills forms to surface tools that only appear after interaction
This is the jump from "what does this site use" to "what is this company actually doing."
Head-to-head: WhatRuns vs TechSpy
WhatRuns genuinely wins the top rows. Here's the full picture, fair:
| WhatRuns | TechSpy | |
|---|---|---|
| Free to use | ✅ Always free | ✅ Free tier, 30 scans/day |
| One-click browser extension | ✅ Yes | ➖ Web app (no install) |
| Instant "what's it run" glance | ✅ Yes | ✅ Static scan in seconds |
| Detection method | HTML / JS fingerprint | JS-runtime + headers + HAR |
| Sees through React/Next.js SPAs | ➖ Thins out | ✅ Yes |
| DNS / DMARC / SPF / DKIM | ➖ | ✅ |
| Subdomain discovery | ➖ | ✅ |
| Sitemap structure | ➖ | ✅ |
| Deep Scan (hidden APIs/SDKs) | ➖ | ✅ |
| Interact (post-click tools) | ➖ | ✅ |
| Output | Raw list | Verdict / Evidence / Implications |
| Confidence markers | ➖ | ✅ High/Med/Low |
| Saved scans / compare / history | ➖ | ✅ |
| Reports (Deep Dive/Comparison/Ranking) | ➖ | ✅ |
| Export PDF / Zapier / API | ➖ | ✅ (Max) |
If all you need is the first three rows, WhatRuns is a great tool. Everything below them is why people move.
Free glance vs work-grade tiers
Straight up: WhatRuns is free. So is TechSpy's entry tier — and even the $0 plan already carries things the extension doesn't.
| Plan | Price | What you get |
|---|---|---|
| WhatRuns | Free | Tech detection via extension |
| TechSpy Free | $0 | 30 scans/day + DNS/sitemap/subdomains + save & compare |
| TechSpy Plus | $19/mo | 10 Deep Scan + 5 Interact credits |
| TechSpy Max | $49/mo | Unlimited scans + 50 Deep Scan + 25 Interact + Export/Zapier/API |
| TechSpy Enterprise | $199/mo | Volume + team needs |
Worth being precise about speed: the static scan returns in seconds. Deep Scan and Interact take minutes — they're doing a real headless render, not a fingerprint lookup. That's the tradeoff for seeing what a fingerprint can't.
When WhatRuns is the better pick
No spin — sometimes it just is.
Stay on WhatRuns if you:
- Want a free, zero-signup, one-click glance while casually browsing
- Only ever check a single site's stack at a time
- Don't hit SPA sites that go blank
- Don't need DNS/infra data, monitoring, or an API
Move to TechSpy if you:
- Keep hitting React/Next.js sites the extension can't read
- Need infra signals — DNS/DMARC, subdomains, sitemap
- Want saved scans, compare, and history to track a target over time
- Need exports, Zapier, or an API to put this into a workflow
If you're in the first list, honestly, don't bother switching. If you're in the second, you already outgrew the extension.
Scan a site you already checked in WhatRuns
Best way to judge the difference is to prove it. Paste a domain — ideally a JS-heavy React or Next.js site that came back thin in the extension — and get TechSpy's full read.
- No extension to install
- No card required
- Free tier is a real product, not a trial wall — 30 scans/day
- Static scan returns in seconds
Scan a domain free
See the opinionated read for yourself — no login, 30 scans/day.