What is the best opening for beginners


As Black I usually play the French-Sicilian (...c5, then ...e6) in response to e4. I've also become interested in the O'Kelly variation, though I have yet to actually test it out.
As White I would play the Scotch sometimes but I kept making the same opening blunder with it and got mad 💀 Now I more commonly go with the Ponziani or the Reti. Keep in mind that the Scotch is still very good — I've definitely had my fair share of good results with it — but you must take care to not be an idiot like me.
There is no “best” opening for beginners.
Learn the basic principles that apply to all openings: develop quickly, control the center, castle, avoid making pawn moves in front of your king.
Try different openings. Use your head rather than an opening encyclopedia. Then check how you did.
You will learn faster and find out what type of opening fits your style.
Good luck.

Opening principles written above are the most important thing. Though, it does feel good to have an opening repertoire. I recommend a system opening so you don't have to learn too many lines.
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The Collie Zuckertort system is a fun aggresive opening as white.
If you are black. Just apply the opening principles and analyse your games. It's not worth learning lines for all the opening you will face at lower levels.

there are a few, you should actually some of them and see which one fits your playstyle more. openings are mostly about what type of middlegame you want to play

Scotch Game or London is more beginner friendly than highly theoretical openings like Italian or Queen's Gambit. For black, I recommend the French Defense over the Caro-Kann because you will only face the Advance, Exchange, Tarrasch, and the Normal 3.Nc3 French. With Caro-Kann, you have to prepare against the Main Line 3.Nc3, Modern 3.Nd2, Fantasy, Two Knights, Advance, Panov and other Exchange lines (4.Bd3, 4.Nf3). Against d4, I suggest the Slav/Semi-slav triangle structure.