Draw fairness · Trust
Online kuji fairness: what to show customers
The question online kuji operators hear most often is ‘Aren't the odds rigged?’ Showing information customers can check for themselves is more convincing than simply saying you're fair. The draw method, disclosed information, and operator permissions need to be designed together.
KUJI BUILDER · Last reviewed
1. Run draws on the server
If results are decided in the customer's browser, someone can tamper with the page to get the result they want. Have the server draw only for orders whose payment is confirmed, and store the final result with the order so it doesn't change on refresh. Server-side randomness alone doesn't prove fairness, so the disclosed information and permission management below are also needed.
- Draw only after payment is confirmed
- Store the final result with the order
- Draw only once even if the same request repeats
- Document how random numbers for draws are generated
2. Show remaining quantities per tier right away
For limited-quantity kuji, remaining quantities per tier are the key to buying decisions. The numbers must drop immediately with every sale, and the sum across all tiers must match the total remaining. Hiding whether top-tier prizes are already gone can actually fuel suspicion.
- Remaining quantities per tier add up to the total remaining
- Screen updates right after each sale
- Showing whether top tiers are sold out
- Odds shown for fixed-odds products
3. Keep win records and decide what to make public
Showing which tier came out and when is evidence that prizes are actually being won. Still, choose the displayed fields so customer names and contact details aren't exposed. Set retention rules so that not even operators can delete records at will.
- Fields to publish: time, tier, prize
- Protecting personal information, e.g. partially masking nicknames
- Record retention period and deletion permissions
- Process for checking per-order results when an inquiry comes in
4. Separate admin permissions and log changes
If prize quantities or odds can be changed during a sale, there must be a record of who changed them and when. Separate permission to list products from permission to change draws and inventory, and consider restricting changes once a board is on sale. Before launch, test that results stay consistent under concurrent purchases and retries.
- Designate who can change draws and inventory
- Log before-and-after values and who made each change
- Rules restricting changes after sales start
- Keep test results for concurrent purchases and retries