When I got my goats, one esp was an escape artist, apparently the lady before couldn't keep her fenced in, which is why I was offered her, as I said they would have to be tethered, but we are away from roads, kids, dogs etc, and they would only be out when I was here to take them in if needed and make sure they had water all the time. we have poisonous shrubs about, which was the main reason. I saw her jump sheep netting, almost sat back on her rear end and launched herself over.
They were on LONG light tethers, started halfway along and extended regularly during the day. RSPCA friend knew and was satisfied they were OK.
Since then I've had fields refenced and an elecric fence about 2ft round the inside. she eyes it up but hasn't tried it yet.
I think minimum of 2, preferably 3 swivels are recommended, put water more or less at the reach of the tether.
The one 'good' thing about it is they are on fresh grass every day, something like rotating round fields to keep internal parasites under control. Also maybe a good thing with new goats till they've settled in.
NEVER go out and leave them vulnerable.