Sandbox vs live mode: what's the difference?
Sandbox is a test environment with fake money and test keys. Live uses real money and production keys. Build and test in sandbox first; the two have separate credentials.
Sandbox lets you exercise the whole flow, including simulated FPX banks and test cards, without moving real money. It has its own API keys, its own webhook secrets and often its own dashboard, so nothing you do there can touch production.
Going live is a credential swap, not a code rewrite: point your integration at the live endpoints, replace every test key with its production counterpart, and re-run one real end-to-end payment. Leaving a single sandbox key in production is one of the most common launch failures.