The casino commits to its secret server seed first by showing you its hash. You then set your client seed. Because the casino couldn't know your seed when it picked its own, it couldn't choose a server seed designed to give you bad results. Your client seed is your share of the randomness.
Changing your client seed changes which results you get - the sequence is completely different - but not how likely any result is. There is no lucky or unlucky seed.
Good habits:
- Replace the default client seed with your own before you start.
- Changing the client seed usually rotates the seed pair, which reveals the old server seed so you can verify past bets.
Example. The same server seed with client seed "alice" and with client seed "alice2" gives two unrelated result sequences. Over 100,000 drops each, both land on the same RTP.
In ProvablyHero tools
The demo lets you edit your client seed and verify every drop. Full test: Does changing client seed change your odds?