That's true, many were. That was mostly in the Caribbean.
There were also (I would say the majority) private ships operating under a government licence, the letter of marque, where they could do anything to the enemy's shipping to "take, burn or destroy". That was mostly in the Channel and the south americas.
And there was a big grey area where a ship might be thieving on one occasion and operating under a letter of marque on another. As with most history, it all depends on who was telling the story afterwards.
There were also (I would say the majority) private ships operating under a government licence, the letter of marque, where they could do anything to the enemy's shipping to "take, burn or destroy". That was mostly in the Channel and the south americas.
And there was a big grey area where a ship might be thieving on one occasion and operating under a letter of marque on another. As with most history, it all depends on who was telling the story afterwards.