SellPolia
SellPolia is the open market for testnet coins — starting with Sepolia ETH (SETH). It lets anyone buy SETH instantly with real crypto, or sell their idle SETH into a queue and get paid in real ETH on Base.
One transparent, on-chain price. No order books to babysit, no counterparties to find — the protocol matches buyers and sellers automatically.
SETH is a testnet asset with no monetary value. SellPolia is a marketplace for buying and selling it. Nothing in these docs is financial advice.
The two sides of the market
- Sellers send SETH to the SethVault on Sepolia. Each deposit becomes one order in a first-in, first-out (FIFO) queue. As buyers arrive, queued SETH is sold in order and the seller accrues a balance that is paid out in ETH on Base.
- Buyers pay through a PaymentCollector on a supported payment chain (with the native asset or a stablecoin). The purchase is filled instantly — from the live seller queue first, and from the SellPolia reserve as a backstop — and the SETH is delivered to the buyer’s Sepolia address.
Why it exists
Sepolia ETH is scarce and awkward to source — faucets are rate-limited and unreliable. SellPolia turns idle SETH into a liquid, priced market: sellers monetize what they aren’t using, and buyers get SETH on demand at a known price.
How the pieces fit together
| Layer | What it is |
|---|---|
| Smart contracts | SethVault (Sepolia), PaymentCollector (payment chains), Payout (Base) — see Smart Contracts. |
| Indexer / backend | Watches on-chain events (WebSocket + getLogs backstop), maintains the queue, matches sales, and drives deliveries & payouts. |
| Web app (dApp) | The buy/sell interface at sellpolia.com . |
| Public API | A read-only HTTP API the dApp (and anyone) can query — see API Reference. |
Where to go next
- New here? Start with Getting Started.
- Want the mechanics? Read How It Works.
- Building on top? See the API Reference and Smart Contracts.
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