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The default is to use version <code class=\"literal\">3.0</code> of the <span class=\"productname\">PostgreSQL</span> protocol, unless the connection string specifies a feature that relies on a higher protocol version, in which case the latest version supported by libpq is used. If the server does not support the protocol version requested by the client, the connection is automatically downgraded to a lower minor protocol version that the server supports. After the connection attempt has completed you can use <a class=\"xref\" href=\"/docs/18/libpq-status.html#LIBPQ-PQFULLPROTOCOLVERSION\"><code class=\"function\">PQfullProtocolVersion</code></a> to find out which exact protocol version was negotiated.</p>\n<p>The current supported values are <code class=\"literal\">3.0</code>, <code class=\"literal\">3.2</code>, and <code class=\"literal\">latest</code>. 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