What Is PyFunceble?

Updated

PyFunceble is a tool for checking the availability or syntax of domains, IP addresses, and URLs. It is aimed at people who need to verify network resources in bulk rather than one at a time — for example, checking whether a long list of domains still resolves, or validating that a set of URLs is well-formed before feeding them into another process.

What it checks

PyFunceble handles two distinct kinds of checks, and it helps to keep them separate:

  • Availability checks — whether a domain, IP, or URL actually responds or resolves. This is about the current state of a resource on the network.
  • Syntax checks — whether a domain, IP, or URL is written in a valid format. This is about the structure of the string itself, independent of whether anything is live at the other end.

A domain can be syntactically valid but unavailable (for example, a well-formed name that no longer resolves), or syntactically invalid and therefore never worth an availability check. Running both kinds of checks is what lets you separate "this is malformed" from "this is fine but currently down."

Who it is for

The tool fits workflows where network resources are handled as lists rather than individually, such as:

  • Auditing a domain portfolio or a blocklist for entries that no longer resolve.
  • Cleaning a dataset of URLs before using it in scraping, monitoring, or analysis.
  • Validating user-supplied or imported domains and IPs for format errors.

If you only ever need to check a single URL by hand, a browser or a one-line command is usually faster. PyFunceble's value shows up when the input is a set.

How to reach it

PyFunceble is provided at pyfunceble.github.io. The page is a JavaScript application, so it requires JavaScript to be enabled in your browser to run — if you open it with JavaScript disabled, you will see a notice asking you to enable it rather than the tool itself.

Practical notes

  • Decide first whether you need an availability check, a syntax check, or both; the answer determines what a "failure" in your results actually means.
  • Treat syntax results as format validation only — a passing syntax check does not imply the resource is reachable.
  • Because the interface is a JavaScript app, plan for a modern browser with scripting enabled.