The last place I worked at had some serious issues going on internally. A couple hundred people but a basically non functioning HR department. People being yelled at by managers without repercussion. Also just bad engineering culture - top down directives that didn't make sense to be spending time on.

About once a month there'd be an extremely negative review show up on glassdoor highlighting what it was actually like. Directors go into crisis mode then a few days later the review is gone. Apparently if you pay Glassdoor you can have reviews removed by just telling them it's not factual. So unfortunately it just can't be trusted.

Nowadays I talk to someone that works there off the record, outside of the interview process. Ideally a friend of a friend.

Glassdoor can be amazing at finding dirt on a company. ALWAYS sort by new. Many companies (unfortunately) incentivize their employees to write five star reviews. Those will show up first if sorted by Best.

Glassdoor is super useful & also just great entertainment