All the casinos recommended in the replies above are reputable casinos. There is no such thing as a completely safe online website, be it a casino, exchange, wallet..
Take your time to read the announcement threads on this section then make up your own mind. You are the only one who can tell which is the best casino based on your own preferences.
Who wants safe casinos? The OP is asking for casinos which are trustable. Hence people are recommending for the same.
It’s always best to avoid casinos which are new in the market, until and unless it’s backed by big people here.
I am not saying that all new casinos are bad, but yes due to some, all gamblers should be aware while playing in these.
The OGs are the best to do gambling. Op can freely visit stake.com if he wants to try wide variety of games in a safe and transparent environment.