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About
Browser-side · queries to public APIs

About PingThat

Last updated: 2026-10-01

What this is

PingThat is a suite of 24 free network and security tools — DNS lookups, WHOIS, SSL certificate inspection, HTTP headers, JWT decoder, subnet calculator, port scan, redirect tracing and a handful of privacy checks. Some tools run entirely in your browser; others necessarily query DNS or fetch a remote host and therefore need network access (your browser's, or a small backend acting on your behalf). The next section spells out exactly which tool does which — no hand-waving claims about "everything happens locally" when a DNS query obviously cannot.

Where each tool runs

PingThat tools fall into five execution buckets. We name them up front because the privacy implications differ:

  • Local tool processing (5 tools) — tool inputs are processed in your browser tab. Loading the website can still involve hosting, analytics and advertising requests as described in the privacy policy.
    subnet-calculator, ip-converter, password-strength, jwt-decoder, url-parser
  • Browser → public STUN server (2 tools) — the WebRTC leak and privacy checks open an RTCPeerConnection against Google's public STUN endpoint (stun.l.google.com:19302) to gather ICE candidates. Surfacing what your browser reveals to a STUN server is the entire point of the test — without the STUN query there is nothing to detect. The STUN service receives network connection data, including the public IP used for the request.
    webrtc-leak-test, privacy-check
  • Browser → Cloudflare DNS-over-HTTPS (5 tools) — your browser sends a DoH query to cloudflare-dns.com/dns-query. The query goes from your IP to Cloudflare, not through a PingThat server. The request does not pass through our tool backend. Recent targets are stored in your browser; a target included in a shareable page URL also reaches hosting when that URL is opened.
    dns-lookup, reverse-dns, caa-lookup, dnssec-check, ipv6-check
  • Browser → third-party HTTP probe (1 tool) — my-ip fetches from ipapi.co and api.ipify.org to identify your public IP plus a few geo/ISP fields. The HTTP request goes from your browser directly to those endpoints (no PingThat proxy), but the data flow is to a different service than the DoH bucket above. Listed separately so the privacy distinction is explicit.
    my-ip
  • Through a PingThat backend (11 tools) — Cloudflare Pages Functions receive the domain, IP address or URL you enter, contact the relevant service or target host, and return the result. These handlers do not write inputs to an application database or query log. Cloudflare and the receiving services still process request and connection data.
    whois-lookup, ssl-checker, port-scan, http-headers, site-speed, email-auth, redirect-checker, resolver-compare, is-it-down, is-it-up, net-ping

Only the first group processes tool inputs without making a network query. The other groups contact external services, either directly or through PingThat. A command-line DNS or host check also sends network requests; running it locally does not make the lookup offline.

Data sources and third-party services

The services contacted depend on the tool:

  • Cloudflare DNS-over-HTTPS — DNS Lookup, Reverse DNS, CAA Lookup, DNSSEC Check and IPv6 Check query it directly from your browser. Email Auth uses it through the backend.
  • Public DNS resolvers — Resolver Compare queries Cloudflare, Google, AdGuard and NextDNS through the backend.
  • RDAP registries — Whois Lookup contacts the registry for the domain through the backend, with rdap.org as a fallback. It uses RDAP over HTTPS, not raw WHOIS on port 43.
  • Cert Spotter and crt.sh — SSL Checker queries Certificate Transparency records through the backend, with crt.sh as a fallback, and also requests HTTPS from the target host.
  • Google Chrome UX Report (CrUX) — Site Speed sends the URL or origin through the backend to retrieve available field performance data. It does not run a live speed test against that host.
  • Target hosts — HTTP headers, availability checks, Net Ping, redirect tracing and port probes send HTTP/HTTPS requests from the backend. Port Scan uses HTTP probes; it cannot verify arbitrary TCP services. Redirect checks also contact the next host in the redirect chain.
  • Google STUN, ipapi.co and api.ipify.org — The WebRTC/privacy tests and public IP tool contact these services directly from your browser, as described above.

Accuracy, caching and rate limits

Results reflect the data source and the time of the query. DNS answers and upstream services can be cached. Certificate Transparency records describe issued certificates and do not by themselves prove which certificate a host currently serves. CrUX reports field data over its collection period, not the speed of one new visit.

Repeating a query or adding a URL parameter does not guarantee fresh upstream data. Cloudflare and upstream services may limit or reject requests; any such result needs to be read in the context shown by the tool.

Why it exists

PingThat brings network checks and local utilities together without signup. Its aim is to make a quick check convenient while explaining where the answer comes from and what it can establish.

Some tools store recent targets in this browser to make repeat checks easier. We do not write a per-user query history to an application database; providers still receive the requests described above.

How it is funded

PingThat is free. It includes Google AdSense support; ad availability depends on Google’s approval, serving decisions and consent signals. You can also support the project through Buy Me a Coffee.

These options do not guarantee revenue or sustainability. The tools remain available without a paid account.

Who is behind it

PingThat is built and maintained by Marco B., an independent developer based in Spain. The site is part of a small portfolio of utility web apps (AllYouNeed for general tools, JSONCraft for developers, OpenImages for image work, OpenPDF for PDFs, PingThat for networking). Each one shares the same private-by-default design.

For errors or suggestions, use the contact form. We do not promise a fixed response time.

Editorial independence

The advertising network (Google AdSense) does not influence which tools are built or how they work. There are no sponsored articles, no "best of" lists pushing affiliate links, no referral kickbacks for VPN or hosting recommendations, and no editorial choices made to favour an advertiser. If a tool exists on the site, it is because it was useful enough to the operator to build and ship it.

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