About & Contact

What this site does

Open the home page and you get the address your connection is currently seen as, the network that announces it, an approximate location, the TLS and HTTP details of the request, and two browser-side checks — WebRTC candidates and which DNS resolver actually answered. There is a tools section for the small conversions developers keep needing: CIDR math, IPv6 expansion, JWT decoding, DNS and RDAP lookups, port numbers, cron expressions.

No sign-up, no account, no dashboard. Everything runs per visit and is discarded when you close the tab.

Why it exists

Every site you visit makes quiet judgements about your traffic: is this a datacenter, is it a proxy, is it worth showing a captcha to. Those judgements are usually invisible, and when they go wrong you have no way to see why a page kept asking you to prove you were human.

This site exists to make that view legible. If a login keeps failing, a form keeps challenging you, or a streaming service refuses to serve your region, being able to see your ASN, your address family and your resolver is usually the fastest way to understand which of them is responsible.

How it is built

The front end is SvelteKit, deployed as a Cloudflare Worker with the site served from the edge. Most of the numbers come from metadata Cloudflare already attaches to the request — ASN, organisation, geolocation, TLS version, HTTP protocol, edge location. Two things deliberately do not come from there: the IP family your connection did not use, and your DNS resolver. Both would be answered by Cloudflare's own egress if the server asked, so the browser asks single-stack hostnames and an EDNS service directly instead.

Some values are simply not available on a non-enterprise plan — TLS fingerprints (JA3 / JA4) being the important one. In that case the row is hidden and the page explains why, rather than printing a placeholder that looks like data.

The one editorial rule

Nothing on this site is invented. Where a signal cannot decide between yes and no, the interface says unknown instead of rendering a confident negative — because "we could not tell" and "no" are different answers, and confusing them is how diagnostic tools become misleading.

The articles follow the same rule. They are written from testing real connections, real VPS instances and real DNS zones, and they name the limits of what was measured. When a claim depends on a provider plan or a vendor decision, the article says so.

Funding and independence

The site is free. A few links on the recommendations page are affiliate links: if you sign up through one, the operator may receive a commission at no extra cost to you. Partners do not see drafts, do not get to review articles, and cannot buy a favourable verdict inside a diagnostic result. If an article recommends a provider, it is because it was used, and the page discloses the affiliate relationship.

Who maintains it

One developer, working under the name GistWillan. The broader personal site — longer notes, other tools, less formal writing — lives at gistwillan.top. This site stays narrow on purpose: a diagnostic page should be fast, boring and predictable, not a portal.

Contact

Email: gistwillan@gmail.com. It is read by the person who writes the code, usually within a few days. There is no ticket system and no support contract, so please keep requests specific.

• Bug report: the URL, what you expected, what you saw, and the browser and OS. If a result looks wrong, the IP or domain involved makes it reproducible.
• Wrong geolocation or classification: include the IP. Carrier-grade NAT and mobile networks produce systematic errors, and those are worth fixing.
• Security issue: describe the class of problem and how to reproduce it, without testing it against other users. Responsible disclosure is welcome and will be credited if you want.
• Content correction: an article that is out of date or wrong is a bug too. Point at the paragraph and the source that contradicts it.
• Legal: use the same address, with "Legal" in the subject line.