Best Free Website Technology Checkers in 2026

By Laurel · Updated Oct 22, 2026

If you just want to know what one website runs, install the Wappalyzer or WhatRuns extension and you'll have an answer in a click, for free. If you want the CMS, server and hosting history of a site without installing anything, W3Techs, Netcraft and BuiltWith each offer a lookup page. And if you want a list of every website that uses a given tool, that's where the free tier ends and paid technographic data begins. This page compares 11 tools on what they detect, what the free tier actually allows, and which reader each one suits.

A website technology checker reads the public code of a page (HTML, scripts, cookies, response headers) and matches it against a library of known fingerprints. That's how it tells you a site runs WordPress, Shopify, Google Tag Manager or Cloudflare. We sorted the tools below by the job you're trying to do, because a developer checking a competitor's checkout and an SDR building a 500-account list from "uses HubSpot" need very different things. Prices and limits come from each vendor's own pages.

This article is about free lookups. For the paid side (lists by installed technology, company-level install base, contacts), see the best technographic data providers and the best BuiltWith alternatives.

Key Facts

• W3Techs says it detects technologies using a combination of regular expressions and DOM traversal with several thousand indicators, and that accuracy can't be 100% because sites can hide their technologies.
• BuiltWith says it tracks 127,890 web technologies across 491.9 million domains (vendor claim).
• WhatRuns reports 450k+ active users for a free extension that needs no sign-up (vendor claim).
• Salesforce's State of Sales report says reps spend almost one full day of the workweek on prospecting, which is why teams filter lists by installed technology instead of guessing.
• The median worker has been with their current employer for 4.1 years, per the US Bureau of Labor Statistics, so any contact attached to a technology record decays on a similar clock.

Two readers, two jobs

Most roundups mix these up. Here's the split we use for every tool in this article.

If you're in the first two rows, the free tools below are probably enough and you can skip anything that asks for a credit card. If you're the third reader, a free checker will show you one site at a time, and the real decision is which paid tool fits. Our guide to choosing sales intelligence software covers that purchase.

Quick Comparison Table

How these checkers detect technology (and what they miss)

Nearly every free checker works the same way, and the shared method explains the shared blind spots.

1. Fingerprinting the page. The tool loads the page, or reads it inside your browser, and looks for known patterns: a wp-content path, a Shopify script, a Google Analytics tag, a header such as X-Powered-By. W3Techs also lists DNS records and Whois data among its indicators, and uses dependencies between technologies, such as inferring PHP from a WordPress site, per its FAQ.
2. Crawling at scale. BuiltWith says it indexes the internet much as a search engine does and doesn't rely on third-party data. W3Techs says it visits sites about once a month and usually crawls a few sample pages, not the whole site.
3. Reading in the browser. Extensions such as Wappalyzer and WhatRuns inspect the page you're on at that moment, including scripts that load after the page renders.

The practical rule: a checker tells you what a visitor's browser could see. It does not tell you what a company runs behind the login. A site can also hide or rename signals, which is why W3Techs says accuracy can't be 100%. Treat any single result as a strong hint, and cross-check surprising answers with a second tool or with your own browser DevTools.

1. Wappalyzer: the free extension that most developers install first

Wappalyzer is the closest thing the category has to a default. Its browser extension is listed for Chrome, Firefox, Edge and Safari and reveals the stack behind any site you visit. The company, Wappalyzer Pty Ltd in Australia, says its coverage is "thousands of web technologies across millions of websites" (vendor claim, no hard count).

The free layer is more generous than most. The extension is free. A free account on the pricing page includes 50 technology lookups and 50 email verifications a month, 5 website alerts and free sample lead lists. The lookup page says a live lookup counts as 5 lookups, distinguishes cached results (those checked within the last 30 days), and that bulk analysis takes up to 100,000 URLs per upload.

Where the free tier stops: paid plans are Pro at $250/mo, Business at $450/mo and Enterprise from $850/mo, all shown monthly. Annual billing saves 17%; ask Wappalyzer for the annual figure. Pro gives one user, 2 lead-list technology targets and 5,000 technology lookups. Business gives 5 users, unlimited targets, 20,000 lookups and CRM enrichment. Plan API credits expire after 60 days.

Best for: developers and marketers checking sites (free), SMB sellers starting list-building (paid). Not ideal for: sales teams that need unlimited lists at a low monthly price.

2. BuiltWith: the deepest free profile per website

BuiltWith is the best-known name in technology lookups, and its single-site profile is the one most agencies reach for when they want history and not just a snapshot. The vendor says it tracks 127,890 technologies across 491.9 million domains, with history going back 41 years (vendor claims).

On the free side, BuiltWith says its tool is free to use for individual site lookups forever, and it publishes free browser extensions for Chrome, Firefox and Edge plus a bookmarklet. The plans page states no numeric cap on free lookups, so confirm any volume you plan to use with the vendor.

Where the free tier stops: the paid plans are built for list-building. Basic is $295/mo or $2,950/yr (2 technologies, 2 keywords, 1 login), Pro is $495/mo or $4,950/yr with unlimited technologies and keywords, and Team is $995/mo or $9,950/yr with unlimited Pro logins. Pricing is flat per account, and annual billing is cheaper than monthly. For cheaper routes to the same lists, see the best BuiltWith alternatives.

Best for: marketers, agencies and analysts who want technology history on a competitor's site, and sales teams ready to pay for lists. Not ideal for: anyone who wants a published free-lookup quota in writing.

3. WhatRuns: the zero-friction extension

WhatRuns does one job and asks for nothing. The home page calls it free with no sign-up required, reports 450k+ active users, and says it shows web apps, CDNs, visitor-tracking methods, WordPress plugins and fonts. It also lets you follow a site and get notified when that site starts or stops using a technology. The page names only an "Add to Chrome" button, so confirm availability on other browsers before you roll it out to a team.

It lists no paid plans, no export and no API. That's a feature for the casual reader and a gap for anyone who wants to move from one site to a list. The page doesn't describe its detection method or publish accuracy figures.

Best for: developers and marketers who want fast answers on competitor sites. Not ideal for: list-building, exports or API workflows.

4. W3Techs Site Info: the checker with a documented method

W3Techs is better known for market-share reports, but its Site Info tool lets you enter a URL and see the CMS, programming language, web server and hosting provider, among other items. The same page offers a bookmarklet, Chrome and Firefox extensions and a Site Info API.

What makes it useful is the methodology. The FAQ explains the fingerprinting approach, the monthly revisit cycle, and the fact that low-usage technologies can produce unreliable statistics. That's more candour than most vendors offer. The lookup page doesn't state a price or usage cap, and the FAQ doesn't address API terms, so confirm commercial or high-volume use with W3Techs through its API documentation.

Best for: analysts and technically minded marketers who want to understand how a result was produced. Not ideal for: lists of accounts or contacts, which it doesn't provide.

5. Netcraft: hosting and infrastructure first

Netcraft sits slightly apart from the others. Its Site Report shows the infrastructure and technologies used by any site, based on Netcraft's internet data mining, and its free browser extension displays site technology and hosting provider alongside anti-phishing protection. The extension is listed for Chrome, Firefox and Edge, and it also gives a risk rating for sites Netcraft hasn't seen before.

That security focus is the difference. Netcraft is the tool you'd open to ask where a site is hosted and whether it looks risky, not to ask which email platform the marketing team picked. Netcraft says use of its site is subject to its Fair Use and Copyright policies, and the Site Report page doesn't state free-use limits, so read those terms before building a workflow around it.

Best for: security, IT and procurement reviewers, and developers who need hosting context. Not ideal for: marketing-stack research.

6. Similarweb (SimilarTech): market share by technology, free

SimilarTech is no longer sold on its own. Its site now reads "A Similarweb Company" and lists free tools including a Technology Checker, which sends you to a Similarweb page. That free checker lets you search for a technology and see its usage and market share, top industries and countries, with stats it says are updated weekly. Its calls to action lead to registration, so expect to create an account for anything beyond a quick search. Similarweb also offers a free Sales Chrome extension.

So this is a "who uses this technology" tool, not a "what does this site run" tool. The paid path is Similarweb Sales Intelligence, with pricing on request. If you land here from an old SimilarTech link, that's the route.

Best for: marketers and strategists sizing a technology's market, and sales teams evaluating Similarweb Sales. Not ideal for: a quick check of one site's stack.

7. WhatCMS: CMS detection with a public API price list

WhatCMS focuses on one question, which content management system a site uses, and it has widened to other technologies. The site says it detects over 1,200 CMS and website-powering technologies (vendor claim). It also links to sister tools for hosting providers, WordPress themes and Shopify themes.

Its API page is one of the clearest in this category. The free plan allows 500 detections with the API limited to 1 URL per 10 seconds and no batch processing or private detections. Paid plans start at $20 a month for 10,000 detections, $40 for 20,000, $80 for 50,000 and $150 for 100,000, and go up to $800 a month for 1,000,000 detections. Prices are monthly. The page says upgrades and downgrades are prorated and paid plans include an ad-free interface.

Best for: developers, agencies and freelancers who need CMS detection in a script. Not ideal for: marketing-stack analysis beyond the CMS.

8. Hunter TechLookup: a technology list that feeds email search

Hunter is best known as an email finder, but it also has TechLookup, and it works in the opposite direction from everything above. According to Hunter's help center, you pick a technology, click "Reveal the websites," and Hunter opens a Discover search with the Technology filter applied. Browsing the list of tracked technologies needs no account, but finding companies by technology requires a paid All-in-One plan and isn't available on the free plan.

So Hunter isn't a single-site checker. It answers "which sites use Shopify?", then lets you pull emails for them. Check Hunter's current plans and see the best Hunter alternatives before committing, and see the best email finder tools for how the credit models compare.

Best for: sales teams who already use Hunter and want technology as a list filter. Not ideal for: anyone who needs a free checker for one URL.

9. Datanyze: not a checker any more, and the trial is only 90 days

Datanyze appears in older "technology checker" lists because it began as technographic prospecting. Its product today is a contact-reveal Chrome extension, and ZoomInfo has owned it since 2018. On its pricing page, Nyze Lite is $0 for a 90-day trial with 10 credits a month and access lost after the trial, so it isn't a permanent free tier. Nyze Pro 1 is $29/mo billed monthly (80 credits) or $21/mo billed yearly (960 credits a year). Nyze Pro 2 is $55/mo billed monthly (160 credits) or $39/mo billed yearly (1,920 credits a year). Prices are per user, a credit is one contact reveal, and yearly plans are non-refundable.

It's in this article so you can rule it out. If your goal is to find out what technology a site runs, use one of the tools above. If your goal is cheap contact reveals while you browse, it's a different job. For the broader contact-data options, see the best B2B data providers.

Best for: individual sellers who want cheap contact reveals. Not ideal for: technology checks or technology-based lists.

10. Apollo.io: a free technology filter on company search

Apollo isn't a checker, but its free plan includes something sellers often want from one: a technology filter on company search, plus enrichment, in the same account. On Apollo's pricing page, the Free plan is $0 with 900 credits per seat a year, granted monthly at 75, which covers light prospecting. Basic is $49 per seat a month billed annually ($65 billed monthly), Professional is $79 annually ($99 monthly), and Organization is $119 annually with a 3-seat minimum. An email costs 1 credit and a phone number 8, and credits don't roll over.

Apollo's data page claims 240M+ contacts and 30M+ companies (vendor claim). Technology data is detected from websites, so it shares the blind spots described above. For plan comparisons see the best Apollo alternatives.

Best for: small sales teams who want a free technology filter with contacts. Not ideal for: developers who want to inspect one site.

11. Browser DevTools: the check that needs no tool

You can answer a surprising share of questions with the browser you already have. Open DevTools (F12 in most browsers), then:

• Network tab: reload the page and filter by domain to see which third-party scripts load (analytics, chat, ads, payments).
• Response headers: click the main document request to read headers such as Server, X-Powered-By and CDN identifiers.
• Sources and Elements: look for framework names, generator meta tags and plugin paths.
• View source: search for wp-content, cdn.shopify.com or a tag manager ID.

DevTools shows exactly what the page loads, with no third-party database in between, which makes it the best tiebreaker when two checkers disagree. The trade-off is time. There's no fingerprint library, no history and no export.

Best for: developers who want ground truth, and anyone double-checking a surprising result. Not ideal for: checking dozens of sites.

Where the free tier stops

Free checkers do one site at a time. The moment your question becomes "show me every company that uses X", you've moved to a different product, and that's where pricing changes shape.

If you're not sure which side of that line you're on, run the free tools first. They'll show you whether the technology signal is strong enough to build a list on. A tool that returns inconsistent results on five sites you know well won't get better at 5,000.

Reader-fit matrix

Stage-fit matrix

Sizing and persona table

Accuracy, credits and compliance

Accuracy. Detection depends on what the site exposes and how recently the tool looked. Ask three questions of any result: how was it detected, when was it last seen, and could the site be hiding it? The 4.1-year median employer tenure from BLS is a reminder that anything attached to a technology record, especially a contact, goes stale. Salesforce's report adds that 46% of sales pros with agents say data quality issues hurt their sales.

Credit models. The free tools meter differently, so compare units rather than prices.

Compliance, kept proportionate. A technology fact about a public website is business information, and checking one site's code is ordinary research. The risk arrives when a tool attaches people to it. Contact details are personal data under GDPR in Europe, PDPA in Singapore, Malaysia and other Southeast Asian countries, and CCPA in California, so lawful basis, notice and opt-out still apply. The French regulator fined Kaspr EUR 240,000 for collecting LinkedIn members' contacts, a reminder that scraping personal data has consequences even for B2B use. For phone outreach, the FTC says Do Not Call civil penalties reach $53,088 per violation, though the registry rule does not apply to business-to-business calls. Rules differ by country, so this is a starting point, not legal advice. Our prospecting strategy guide covers the workflow side.

How to Choose: Decision Framework

Before you build a list, define who you're targeting. Our ideal customer profile guide helps you decide which technology signals actually predict a fit.

What to Do Next

Pick five websites you know well, three of your own or your clients' and two competitors, and run them through Wappalyzer, WhatRuns and W3Techs Site Info. Compare the results against DevTools on the pages where they disagree. If the tools agree and the technology you care about shows up reliably, you've found a signal worth building on, and the next step is a paid technographic tool or a BuiltWith alternative. For the wider category, return to the sales intelligence hub.