« tbh » is short for « to be honest ».
tbh stands for « to be honest ». It prefaces an opinion the writer expects to land badly: « tbh I didn't like it ».
It is a hedge, not a claim about honesty. Used too often it has the opposite effect — if every third sentence is flagged as honest, the others are not.
Written out, it is « to be honest », usually followed by a comma: To be honest, I didn't like it. The longer form to be honest with you is warmer. In formal writing the phrase is usually cut altogether: state the opinion and let it stand.
Here is what CorrectSMS does with a message containing « tbh ». The correction and the explanations are the app's own.
tbh i dont think its a good idea but its you choice
To be honest, I don't think it's a good idea, but it's your choice.