Used in casual conversations, not in formal reports or official announcements. I found this great cafe by word of mouth from friends.
Pro Tip 2/3
Personal Trust
Implies a level of trust or endorsement when shared between individuals. He’s a reliable mechanic, I know him only by word of mouth from satisfied customers.
Pro Tip 3/3
No Official Record
There's usually no documentary evidence when information is communicated by word of mouth. Many family recipes are passed down by word of mouth, without written instructions.