Belong CheckIn
Sponsored Gas
Complete an NFT mint or check-in payment without holding the native gas token — Belong covers the network gas.
Overview
Sponsored gas lets eligible users complete supported on-chain actions — like an NFT mint or a check-in payment — without holding the native gas token for the network. Belong sponsors only the network gas; you still pay any ticket, NFT, or venue payment amount.
This flow is in beta. Exact limits and enabled scenarios may change during testing.
What sponsored gas does and doesn't do
- ✅ Belong covers the technical cost of the blockchain transaction (gas)
- ❌ Belong does not pay for your purchase
- ❌ Belong does not pay a venue or collection purchase on your behalf
- ✅ For eligible promoter reward withdrawals, Belong may submit the withdrawal transaction and charge only the sponsor's gas bank for network gas
If a flow has a paid amount, you still need funds for that payment (or you can pay through the card flow).
Who does what
| Actor | Responsibility |
|---|---|
| You | Sign the operation and pay for the item, ticket, or payment amount |
| Belong CheckIn | Shows the gasless flow, checks whether sponsorship is available, and submits the operation |
| Belong API | Maintains the sponsorship ledger; checks permissions, settings, and limits; records actual gas usage |
| Gas sponsor | Sponsors gas on-chain after server-side approval |
| Gas bank | Shared sponsorship wallet that funds sponsored gas |
What's sponsored in beta
| Flow | What's sponsored | What you pay |
|---|---|---|
| NFT mint with ERC-20 price | Gas for approve and mint (when enabled and eligible) | The NFT price in the token |
| NFT mint with native price | Not sponsored | Native value and gas |
| Check-in card flow | Gas for the ERC-20 approval | Payment via the checkout widget |
| Check-in wallet flow | Approved low-gas ERC-20 cases | The payment amount |
| Promoter reward withdrawal | Gas for the withdrawal when the venue sponsor enables it | No purchase amount; rewards come from the venue campaign balance |
Why it's safe
Sponsorship is validated entirely on the server — the frontend can't inflate spending or choose where the budget goes:
- The frontend never picks the sponsor wallet or the amount to deduct
- Belong API resolves the sponsor from the venue or collection
- It checks that the signed-in user owns the wallet used, that sponsorship is enabled, and that the operation type and token/spender/amount match
- A budget is reserved before spending, so the same balance can't be used twice in parallel
- Gas is only sponsored after the server approves the exact operation
- After the receipt, only the actual gas used is recorded against the ledger
Related
- Sponsored Gas Ledger Guide — the developer view of eligibility checks and usage recording
- Wallet & Sign-In