> For the complete documentation index, see [llms.txt](https://docs.lighter.xyz/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.lighter.xyz/developers/binary-options/overview.md).

# Overview

Discover, trade and settle Up/Down binary options on Lighter.

{% hint style="info" %}
**Lighter on Robinhood Chain**

Binary options are available on Lighter only. Lighter on Robinhood Chain does not list binary options markets or serve the binary options endpoints.
{% endhint %}

Binary options markets have two outcomes. A winning share pays `1.00` USDC; a losing share pays `0`. Orders use the same transaction types and signing flow as other Lighter markets. See [Signing transactions](/developers/integration-guides/signing-transactions.md) for client setup and transaction submission.

**Up/Down** markets compare an underlying asset’s Chainlink price at the start and end of an observation window. Each window has a new market. Up wins if the closing price is at least the opening price; otherwise, Down wins.

Discover listed series and their observation windows through [events](https://docs.lighter.xyz/api/binary-options). The asset names and durations used in these guides are examples; read each series’ configuration from the API.

## Core concepts

| Concept    | Binary options                                                                                                                                                                                                                                            |
| ---------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| Market     | One order book per window. `market_type` is `binary_options`, symbol `<ASSET>-UPDOWN-<DURATION>-<WINDOW START>` (window start in Unix seconds), e.g. `ETH-UPDOWN-15M-1792436400`                                                                          |
| Price      | Price of one **Up** share in USDC, from `0.01` to `0.99` with a `0.01` tick (`price_decimals = 2`). It can be read as the market-implied probability of Up                                                                                                |
| Size       | Number of shares. Read `size_decimals`, `min_base_amount` and `min_quote_amount` from each market returned by `events`. For example, mainnet markets checked on October 19, 2026 use four decimals, a 5-share minimum and a `0.000001` USDC quote minimum |
| Buy / Sell | Buying opens or adds to an **Up** position and costs `price × size`. Selling opens or adds to a **Down** position and costs `(1 − price) × size`. Trading the other side reduces your position first                                                      |
| Payout     | `settlement_cap = 100` ticks (`1.00` USDC) per winning share, `0` per losing share, paid to the USDC balance at settlement                                                                                                                                |
| Collateral | Every order and position is fully funded from the USDC balance. No leverage, funding or liquidation                                                                                                                                                       |
| Operator   | `operator_account_index` creates and settles the market. Lighter operates the Up/Down series                                                                                                                                                              |

A `market_id` is never reused. Settled markets stay queryable, including their outcome.

{% hint style="info" %}
Use [events](https://docs.lighter.xyz/api/binary-options) to discover binary options markets. They are excluded from the unfiltered [orderBooks](https://docs.lighter.xyz/api/orders) listing and from [orderBookDetails](https://docs.lighter.xyz/api/orders), even when a market ID is supplied to `orderBookDetails`. `orderBooks?market_id=<id>` does return an individual binary options market, but its fee fields read `0.0000`; use the market fees returned by `events`. See [Discover markets](/developers/binary-options/discover-markets.md).
{% endhint %}

## Integration guides

| Guide                                                                              | Covers                                                              |
| ---------------------------------------------------------------------------------- | ------------------------------------------------------------------- |
| [Discover markets](/developers/binary-options/discover-markets.md)                 | Events, market IDs, trading windows and underlying price candles    |
| [Trading and fees](/developers/binary-options/trading-and-fees.md)                 | Order parameters, collateral, restrictions and fee calculations     |
| [Positions and settlement](/developers/binary-options/positions-and-settlement.md) | Account positions, settlement payouts and realized PnL              |
| [Partner attribution](/developers/binary-options/partner-attribution.md)           | Client approvals, integrator fees and reporting                     |
| [WebSocket](/developers/binary-options/websocket.md)                               | Market statistics, underlying candles and existing account channels |

## Integration checklist

1. Discover tradable windows with `events?tag=…&active=true&sort=start_at&order=asc`. Cache each market's ID, trading window and decimals; refresh discovery as windows roll over.
2. If you charge partner fees, check that the client's `ApproveIntegrator` sets `max_spot_taker_fee` and `max_spot_maker_fee` at or above the rates you request.
3. Send limit or market orders with integer prices and sizes. Up/Down markets use prices from `1` to `99` and four decimal places for shares. Reduce-only, stop and TWAP orders are unsupported.
4. Stop submitting new orders when the trading window ends or the market leaves `active`. Track the market through settlement.
5. Read positions from `bo_positions`, settlement records from `trades`, and realized PnL from `portfolio/boPnl`.

Partners who want to create and settle their own binary options series need market slots assigned by Lighter. Contact the team to operate a series.


---

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