etld1

A tiny command-line tool that extracts the registrable domain (eTLD+1) from URLs or hostnames using the Mozilla Public Suffix List.

Example:

sub.service.example.co.uk → example.co.uk
https://deep.nested.example.com/path → example.com

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Install

Prebuilt binaries

Download the latest release for your platform from the Releases page.

From source

git clone https://github.com/Firefishy/etld1.git
cd etld1
go build -o etld1 .

Or with GoReleaser installed:

goreleaser build --snapshot --single-target --clean

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Usage

Pipe domains or URLs into the program. Each line outputs the base registrable domain.

echo 'sub.service.example.co.uk' | ./etld1
# example.co.uk

echo 'https://deep.nested.example.com/path' | ./etld1
# example.com

cat urls.txt | ./etld1

Lines that do not parse as a URL or domain are silently skipped.

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Why?

When normalising URLs, it’s often important to reduce them to the domain users actually control. For example, co.uk is controlled by the registry, but example.co.uk is registrable. This tool uses the official PSL (via Go’s x/net/publicsuffix) to get the correct base domain.

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License

MIT