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A simple library and command-line tool to check domain name availability in bulk using the RDAP protocol, a simple protocol meant to replace WHOIS.

This module is also available on

Usage screenshot


Using Deno

Run once using:

deno run --allow-net

Compile the client into a portable executable using:

deno compile -o rdapcheck --allow-net

Install the client using:

deno install -n rdapcheck --allow-net


Binary executables are available for the latest release.


rdapcheck [OPTIONS] DOMAINS...

The available options are:

  • -q or --quiet: Only print the names of the domains that are available
  • -p or --progress: Print the number of domains processed so far
  • -c or --chunk-size: The number of domains to process in parallel. Set to 10 by default

DOMAIN can be a domain name or a pattern with wildcards that rdapcheck will fill in with every possible value.

The available wildcards are:

  • *: Matches any letter, number or hyphen, "-"
  • ?: Matches any letter
  • #: Matches any number


Check the availability of a single domain

$ rdapcheck is not available

Check the availability of multiple domains with a single command

$ rdapcheck is not available is not available is available is not available

Only print the names of the domains that are available

$ rdapcheck -q

Check the availability of all domains that match a list of patterns

$ rdapcheck -q 'ex?' ''


This tool was completed over the course of one afternoon by referring to the following sources:

For more information on the latest standardization efforts on RDAP, see the RFC Editor's RDAP page.