Sponsor relayer

Sponsor relayer (or simply relayer) is the third party that pays the gas for a user in gasless TON scenarios. Technically the relayer is a separate wallet or server that holds its own TON reserve; it accepts a user-signed intent, wraps it into a full internal message and submits it to the network, spending its own TON on the fee. The user can hold zero TON in their wallet and still transact.

How it works on Wallet V5

The design relies on extensions in the W5 contract — the fifth version of TON’s standard wallet contract:

• the user installs an extension in their W5 wallet, granting it the right to send messages on their behalf;
• the relayer is either that extension itself or an address authorised by it;
• the user signs an off-chain intent (for example, “send 10 USDT to address X”); the signature is passed to the relayer off-chain;
• the relayer builds an internal message, attaches the user’s signature, pays the TON gas, and submits it on-chain;
• the blockchain accepts the message from the relayer and invokes the user’s wallet contract, which validates the signature and executes the action.

On-chain the operation looks like a normal transaction initiated by the user’s wallet contract, but the gas was paid by the relayer.

How relayers monetise

• Subscription. Tonkeeper Battery works this way: the user buys “charge” in USDT, TON or by card and spends it on gas.
• Jetton-denominated fee. Some gasless-USDT schemes take their fee out of the transfer itself (for example, sending 100 USDT — the relayer keeps 0.2 USDT plus the gas equivalent).
• Free (promotional). Some dApps pay the gas for the user as a marketing campaign or as part of onboarding.

Why it matters

• UX. A user buys USDT and can send straight away — no need to buy “technical” TON just for fees.
• Mass payments. Shops and services accept USDT and decide on their own how to pay the fees.
• Mini-app onboarding. Telegram bots and mini-apps can accept a first payment from a freshly registered user without requiring them to hold TON.

Risks and trade-offs

• Centralisation. A relayer is a live service; its downtime means gasless is unavailable.
• Censorship. A relayer can refuse to serve a request; the user always retains the option of submitting a transaction directly via any TON wallet (if they hold TON).
• Compliance. If the relayer operates in a regulated payments jurisdiction, its duties may expand to AML checks on sender or recipient.
• Replay attack surface. Relayer-based designs require careful protection against re-submitting the same signature; bugs here are critical to fund safety.

Notable examples

• Tonkeeper Battery — native relayer inside the Tonkeeper wallet.
• Wallet (in Telegram) — built-in gasless USDT transfers.
• DEX routing through STON.fi and DeDust in gasless mode — dApp-level relayers run by the platform.