If you use network shares with your Mac, there is a little manipulation that seems necessary, because Apple has decided for obscure reasons not to do it for you: disable support for the SMB “1” protocol.

A protocol abandoned by Microsoft

The first version of the SMB protocol — Server Message Block — is very old and its development started in the 80s. It was popularized by Windows 2000 and considered obsolete in 2013. In fact, Microsoft started disabling the default protocol in 2017 with Windows 10, and NAS and other servers (like the Freeboxes) have gradually left the protocol on the side over time to force SMB2 and SMB3. Except Apple.

A matter of security

As well explained by Microsoft on his site, SMB1 is outdated, insecure — there are many flaws — and slower than other versions. The company therefore recommends that it no longer be used.

But macOS, by default, still uses SMB1. A Apple website page happily explains how to do it, hoping that a future version of the OS no longer requires this manipulation. In the Terminal, simply type the following two lines, before restarting the Mac.

echo "[default]" | sudo tee -a /etc/nsmb.conf
echo "protocol_vers_map=6" | sudo tee -a /etc/nsmb.conf

It looks like this in nano

If you’re used to the command line, both lines will create the file /etc/nsmb.conf (absent by default) and add two lines.


The default is 7 and indicates that the SMB1, SMB2 and SMB3 protocols are accepted. The value 6 only enables SMB2 and SMB3 variants and if you are sure that your devices all support SMB3, it is even possible to force the value 4 (SMB3 only). If you ever have trouble connecting to old NAS or network shares, it’s still possible to re-enable SMB1 support — even if it’s a bad idea — by replacing the 6 by a 7 in the file or by deleting the file in question in the Terminal before restarting, with the following command.

rm /etc/nsmb.conf

The different values.

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