# `PublicSufx`
[🔗](https://github.com/reisub/public_sufx/blob/v0.7.20260725/lib/public_sufx.ex#L1)

Implements the publicsuffix algorithm described at https://publicsuffix.org/list/.

# `prevailing_rule`

```elixir
@spec prevailing_rule(String.t()) :: nil | String.t()
```

Parses the provided domain and returns the prevailing rule based on the
publicsuffix.org rules. If no rules match, the prevailing rule is "*",
unless the provided domain has a leading dot, in which case the input is
invalid and the function returns `nil`.

## Examples

    iex> prevailing_rule("foo.bar.com")
    "com"
    iex> prevailing_rule("co.uk")
    "co.uk"
    iex> prevailing_rule("foo.ck")
    "*.ck"
    iex> prevailing_rule("foobar.example")
    "*"
    iex> prevailing_rule("foo.github.io")
    "github.io"

# `public_suffix`

```elixir
@spec public_suffix(String.t()) :: nil | String.t()
```

Extracts the public suffix from the provided domain based on the publicsuffix.org rules.

## Examples

    iex> public_suffix("foo.bar.com")
    "com"
    iex> public_suffix("foo.github.io")
    "github.io"

# `public_suffix?`

```elixir
@spec public_suffix?(String.t()) :: boolean()
```

Returns true if the supplied domain is a public suffix based on the publicsuffix.org rules, false otherwise.

## Examples

    iex> public_suffix?("foo.bar.com")
    false
    iex> public_suffix?("com")
    true
    iex> public_suffix?("foo.github.io")
    false
    iex> public_suffix?("github.io")
    true

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*Consult [api-reference.md](api-reference.md) for complete listing*