How to know Company's work culture before joining?

Interview process is the window into their culture

Reach out to people on Linkedin. Ask the recruiter to connect with existing employees.

It’s important to learn about your team. Some companies have great culture but particular teams can be toxic because of a few employees.

I try to talk to someone in the company and find more details.

Ask if you can work from their office for a day or two. A company called Almabase does this and also has a very interesting Culture interview round. It was a great experience.

A couple of points I can share ( sign of red flag )

1. You are asked to leave the current company before the notice period / asked to join ASAP.
2. You are introduced to the current set of problems under the pretext of getting you warmed up or preparing you.
3. Interview calls are lined up in rush
4. Multiple interviews with the same person or too many interviews..5 to 6 rounds
5. HR not leading the entire process

there is no such thing as a company's work culture, it's always about the team you are going to join and the people you are going to work with, find out about that.

I usually reach out to folks who are working in the same department

Check Instagram handles and hashtags and see if there are candid pics etc for random days.