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

# Discovering and Trading Markets

### Events

Binary options markets are grouped into **events**. An event describes the question being asked (title, description, start and end of its window) and links to the market or markets that trade it. For Up/Down markets, each window of a series is one event with one market.

* Events of the same series share a **tag**, for example `btc-updown-15m` or `eth-updown-15m`.
* The event `start_at` and `end_at` are the window the outcome is measured on, in Unix milliseconds. Trading can open earlier than `start_at`.
* The event metadata carries presentation details such as the underlying, the price provider and feed, and once known the start and settlement prices.

### Finding markets

1. **List events.** Query the events endpoint by tag to get the upcoming and live windows of a series, sorted by start time. Each event includes its order books with their `market_id`, symbol, status, trading hours, fees, decimals and live stats.
2. **Pick a market.** Use the event window to choose the market you want to trade, then use its `market_id` everywhere else, like any other Lighter market.
3. **Follow the underlying.** Live and historical prices of the underlying for each series are available as 1-second and 30-second candles, so you can track the price against the start price during the window.

Settled markets stay queryable by `market_id`, including their outcome.

### Lifecycle of a market

<table data-search="false"><thead><tr><th>Stage</th><th>API status</th><th>Description</th></tr></thead><tbody><tr><td>Listed</td><td><code>inactive</code></td><td>The market exists but is not open for trading yet.</td></tr><tr><td>Open</td><td><code>active</code></td><td>Orders can be placed, modified and cancelled.</td></tr><tr><td>Closed</td><td><code>waiting-for-settlement</code></td><td>The window has ended. Orders can only be cancelled while the market waits for its outcome.</td></tr><tr><td>Settling</td><td><code>in-settlement</code></td><td>The outcome is set. Remaining orders are cancelled and positions are paid out.</td></tr><tr><td>Settled</td><td><code>settled</code></td><td>Every position has been paid. The market keeps its <code>market_id</code> and settlement result.</td></tr></tbody></table>

### Trading

Binary options trade on the same order book infrastructure, API and signing flow as perpetual and spot markets.

* **One book per market.** Prices are the price of an Up share, from `0.01` to `0.99` USDC with a `0.01` tick. Sizes are in shares.
* **Buy for Up, sell for Down.** Buying opens or adds to an Up position and costs `price` per share. Selling opens or adds to a Down position and costs $$1 - \text{price}$$ per share. Trading the opposite side reduces your position first.
* **Order types.** Limit and market orders are supported. Reduce-only, stop and TWAP orders are not.
* **Trading hours.** Orders can only be placed or modified while the market is `active`. Cancels are always accepted.
* **Minimum size.** Orders must respect the market's `min_base_amount` and `min_quote_amount`, and its size and price decimals.
* **Collateral.** Every order and position is fully funded from your USDC balance. Buy orders reserve $$\text{price} \times \text{size}$$ and sell orders reserve $$(1 - \text{price}) \times \text{size}$$.

Binary options positions are shown with your other positions in the account endpoints and WebSocket channels.

### Settlement

When the window ends, trading stops and the operator settles the market with the outcome measured from the price source. Open orders are cancelled, and each position is paid out automatically to the account's USDC balance:

<table data-search="false"><thead><tr><th>Position</th><th>Settles Up</th><th>Settles Down</th></tr></thead><tbody><tr><td>Up shares</td><td>1 USDC per share</td><td>0</td></tr><tr><td>Down shares</td><td>0</td><td>1 USDC per share</td></tr></tbody></table>

In exceptional cases where an outcome cannot be determined, a market can be settled at its default price, paying `0.50` USDC per share to both sides.

### API

For endpoints, WebSocket channels and field descriptions, see the [binary options API documentation](https://apidocs.lighter.xyz/docs/binary-options).