Is working in a casino or betting company haram?

When you buy a product from a company that also does something prohibited, your money flows to them and the transaction is over. A salary flows in the opposite direction: it is paid to you specifically in exchange for work you performed. The character of the work therefore attaches to the income in a way it does not for an ordinary purchase. This is why scholars ask what you personally do all day, rather than only asking who signs the cheque.

Legality under national law and permissibility under Islamic law are separate questions. Gambling is legally licensed in many countries and remains prohibited in Islam regardless. Local law matters for a different reason: it affects your notice period, contractual obligations and whether leaving abruptly would expose you to a penalty. Fulfilling a lawful contractual obligation while you exit is generally treated as part of leaving responsibly, not as prolonging the sin.

It changes the surface, not the substance, if the software you build is the gambling product. Writing the wagering engine, the odds feed, the payment rails for deposits, or the recommendation system that increases betting frequency is directly enabling the prohibited activity - arguably more so than a single dealer, because the code operates at scale. Engineers sometimes assume technical distance equals religious distance. It generally does not. If your work is on a genuinely separate product line with no gambling function, that is a different and more open question.