Privacy
PathLens has no accounts, no sign-up, no cookies and no advertising. It counts page views with a small first-party script that sets nothing on your device and is described in full below. This page describes exactly what leaves your machine, and for which tool, so you can decide what to paste into it.
The short version: most tools run entirely in your browser and send nothing anywhere. Four tools send the specific input you give them to a server in order to answer, and one of those also contacts a third-party IP service. The table below says which is which.
What each tool sends
| Tool | Leaves your browser? | What is sent |
|---|---|---|
| Subnet Calculator | No | All maths runs locally in JavaScript. |
| Bit Calculator | No | All maths runs locally in JavaScript. |
| MAC Vendor Lookup | No | The IEEE registry is downloaded once and searched in your browser. |
| BGP/ASN Lookup | Yes | The IP or prefix you enter. The landing page also asks ifconfig.me for your public IP to pre-fill the field. |
| BGP Route Observer | Yes | The prefix or ASN you enter, used to query public routing data. |
| TLS & Certificate Inspector | Yes | The hostname you enter. The server connects to that host to read its certificate. |
| Local Diagnostics | Yes | The diagnostic JSON you paste in. See the note below. |
Local Diagnostics deserves its own note
The collector script runs on your machine and writes a file locally; the script itself uploads nothing. When you paste that file into the web page, its contents are sent to the PathLens server to be analysed.
That file describes your network: interface names, local and public IP addresses, routing table, DNS servers and traceroute hops. Read it before pasting it, and redact anything you would not want to send.
Third-party services
The landing page requests your public IP address from
ifconfig.me to pre-fill the lookup field. That request goes
directly from your browser to that service and is therefore visible to
it. No other third party is contacted, and no third-party analytics,
tag manager, advertising or social-media script is loaded on any page.
The usage counting described below is served from this domain and sends
nothing to anyone else.
AI-generated explanations
Some tools can explain their results in plain English. When that feature is enabled, the findings for your query are sent to Anthropic's API to produce the wording.
The feature is currently disabled, and tools that support it show a hollow circle on the landing page and say so in the tool itself.
Storage on your device
PathLens sets no cookies and uses no persistent local storage. Nothing is kept after you close the tab. This is still true with usage counting enabled: it stores no identifier, so it cannot recognise you on a second visit or link two visits together.
Usage counting
Most PathLens tools run entirely in your browser and never contact a server, which means there is otherwise no way to know whether anyone uses them at all. To answer that, each page requests a 1×1 image from this same domain with a few facts attached. There is no analytics company involved and no data leaves this site.
What is attached to that request:
- which tool or page you opened, and the page language
- a screen category — phone, tablet, laptop or desktop — never your exact screen or window size
- the host you arrived from, such as a search engine or
news.ycombinator.com, never the full link - whether you interacted with the tool at all, and roughly how long you stayed, rounded into one of four buckets
What is never attached: anything you type into any tool, your exact
screen size, any cookie, and any identifier that would let two visits
be connected. Sending Do Not Track disables it entirely.
Server-side logs
PathLens does not build profiles of visitors. Requests pass through AWS CloudFront, a web application firewall and AWS Lambda; those AWS services keep their own access and operational records, which include IP addresses and browser user-agent strings, under AWS's privacy notice. That data is used for availability, abuse prevention and the usage counting described above — not analysis of individuals — and is not sold or shared. Access logs are deleted automatically after 90 days.
Source code
PathLens is open source. Rather than take this page on trust, you can read exactly what each tool does at github.com/doubleoboyle/netscope.