IN RDAP WE TRUST

My cheap way of checking whether a domain is available to be purchased or not. Used by subjack to confirm takeover targets are registrable.

Availability is checked with RDAP first (RFC 9083): the answer is carried by the HTTP status itself — 404 means the domain is not registered, 200 means it is. RDAP servers are discovered from the IANA bootstrap file and cached per TLD, so there is no per-TLD configuration to maintain and no registry response text to fingerprint. TLDs without RDAP fall back to a small whois client (RFC 3912) that discovers authoritative servers via IANA referral and matches a short list of generic "available" responses.

The only dependency is golang.org/x/net (for public suffix data). Requires Go 1.25 or newer.

This package might not be able to check the availability of every possible domain TLD. Always double-check results manually before acting on them.

go get github.com/haccer/available

package main

import (
        "fmt"
        "time"

        "github.com/haccer/available"
)

func main() {
        // Domain uses a 10s timeout.
        if available.Domain("dreamdomain.io") {
                fmt.Println("[+] Success!")
        }

        // ...or supply your own timeout.
        available.DomainTimeout("dreamdomain.io", 5*time.Second)

        // SafeDomain also reports whether the TLD has no usable whois/RDAP
        // server ("bad" TLD), so you can skip or flag it.
        avail, badTLD := available.SafeDomain("dreamdomain.io")
        fmt.Println(avail, badTLD)
}

All functions are safe for concurrent use: subdomains are reduced to their registrable domain (eTLD+1) first, and the bootstrap data and whois servers are resolved once per TLD and cached.

The test suite runs entirely offline against local RDAP and whois fixtures:

go test -race ./...