> ## Documentation Index > Fetch the complete documentation index at: https://docs.tradingapi.dev/llms.txt > Use this file to discover all available pages before exploring further. # Preview an order > Runs an order without placing it. The body is the same as for placing an order; `client_order_id` is optional and ignored. Nothing is recorded or sent. The preview checks the request, your key's limits and your balance, sizes the order as it would be sized now, and estimates the fill from the current order book. It returns the position and balance you would have afterwards. A preview answers `200` whenever the body is a JSON object. When the order would be refused, `valid` is `false` and `errors` lists every reason at once, with the same error objects placing it would return. ## OpenAPI ````yaml /openapi.yaml post /v1/orders/preview openapi: 3.1.0 info: title: Trading API license: name: Proprietary identifier: LicenseRef-Proprietary version: '1' summary: Trade perpetual futures on Hyperliquid with plain HTTP requests. description: > The Trading API places market orders on Hyperliquid perpetual futures and reports your positions, fills and balance. You never sign anything, manage nonces or look up asset indexes: send a market, a side and a value in US dollars. Every request authenticates with an API key created on the account page: `Authorization: Bearer tapi_…`. servers: - url: https://tradingapi.dev description: Production. Orders trade real money on Hyperliquid mainnet. security: - apiKey: [] tags: - name: Markets description: The markets you can trade, with their rules and current prices. - name: Orders description: Place, preview, list and look up orders. - name: Positions description: Your open positions, and closing them. - name: Account description: Your balance, the calling key, fills and withdrawals. paths: /v1/orders/preview: post: tags: - Orders summary: Preview an order description: > Runs an order without placing it. The body is the same as for placing an order; `client_order_id` is optional and ignored. Nothing is recorded or sent. The preview checks the request, your key's limits and your balance, sizes the order as it would be sized now, and estimates the fill from the current order book. It returns the position and balance you would have afterwards. A preview answers `200` whenever the body is a JSON object. When the order would be refused, `valid` is `false` and `errors` lists every reason at once, with the same error objects placing it would return. operationId: previewOrder requestBody: required: true content: application/json: schema: $ref: '#/components/schemas/PreviewOrderRequest' examples: market: summary: What would $5,000 of BTC do? value: market: BTC side: buy type: market value: '5000.00' responses: '200': description: The preview. content: application/json: schema: $ref: '#/components/schemas/OrderPreview' examples: valid: summary: An order that would be placed value: object: order_preview valid: true order: market: BTC side: buy type: market requested_value: '5000.00' reduce_only: false size: '0.0592' price: null price_limit: '84430' estimate: average_fill_price: '84018.2' price_impact_bps: '1.0' value: '4973.88' fee: '7.212126' position_after: direction: long size: '0.0692' entry_price: '83938.1' value: '5814.06' account_after: available: '331.27' notes: [] errors: [] invalid: summary: An order that would be refused value: object: order_preview valid: false order: null estimate: null position_after: null account_after: null notes: [] errors: - type: permission code: key_order_limit_exceeded message: >- This key may place orders of up to $250.00; this one is $5,000.00. param: value hint: >- Send a value of at most $250.00, or raise the key's limit on the account page. details: max_order_value: '250.00' value: '5000.00' errors: [] retryable: false doc_url: >- https://docs.tradingapi.dev/api-reference/errors#key_order_limit_exceeded '400': description: The body is not a JSON object. content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' '401': $ref: '#/components/responses/Unauthorized' '429': $ref: '#/components/responses/RateLimited' '503': $ref: '#/components/responses/Unavailable' components: schemas: PreviewOrderRequest: type: object description: >- The same body as placing an order. `client_order_id` is optional and ignored. required: - market - side - type - value additionalProperties: false properties: client_order_id: 37e15384-8c6b-496e-b6cf-197fbb071ee8 market: db6c7361-1d0a-4d67-84ef-57c1fbf4df03 side: ef2d1918-729a-4c81-b3d7-f4d3b7dc3d05 type: 898395c4-012c-4af0-8f06-26fa3e7533e5 value: 6df3eeeb-24bc-46cd-af6d-97de6db57cd8 price: 7c53e282-3cd4-4edd-b6a7-364f3aab4b03 reduce_only: 8883b8ab-f5c2-44c5-8dde-53d78bdb2cd3 metadata: f4cf9425-e26f-4ebf-9fdf-155bf6cf561f OrderPreview: type: object required: - object - valid - order - estimate - position_after - account_after - notes - errors properties: object: type: string const: order_preview valid: type: boolean description: Whether placing this order now would be accepted. order: type: - object - 'null' description: The order as it would be sized now. properties: market: type: string side: $ref: '#/components/schemas/Side' type: $ref: '#/components/schemas/OrderType' requested_value: type: - string - 'null' reduce_only: type: boolean size: type: string price: type: - string - 'null' price_limit: type: string estimate: type: - object - 'null' description: The expected fill, from the current order book. properties: average_fill_price: type: string price_impact_bps: type: string description: How far the average fill is from the mid, in basis points. value: type: string fee: type: string position_after: type: - object - 'null' description: >- Your position if the order fills as estimated. `null` if it would close the position. properties: direction: type: string enum: - long - short size: type: string entry_price: type: string value: type: string account_after: type: - object - 'null' properties: available: type: string notes: type: array items: $ref: '#/components/schemas/Note' errors: type: array description: Every reason the order would be refused, when `valid` is `false`. items: $ref: '#/components/schemas/Error' ErrorResponse: type: object required: - error properties: error: $ref: '#/components/schemas/Error' Side: type: string enum: - buy - sell OrderType: type: string enum: - market - limit description: > `market` fills now at the best available prices, within 0.5% of the current price. `limit` fills now at your `price` or better; whatever cannot fill at once is canceled. Note: type: object required: - code - message description: > Something worth knowing about a response that did not stop it. `available_low`, `partial_fill_likely` and `trading_approval_expiring` appear on previews only. properties: code: type: string enum: - size_rounded - price_rounded - position_flipped - position_closed - available_low - partial_fill_likely - trading_approval_expiring message: type: string Error: type: object required: - type - code - message - param - hint - details - errors - retryable - doc_url properties: type: type: string enum: - invalid_request - authentication - permission - not_found - conflict - unprocessable - rate_limited - unavailable - internal description: The kind of error. It determines the HTTP status. code: type: string description: >- A stable identifier for the error. Branch on this. New codes may be added. message: type: string description: What was wrong, with the values involved. param: type: - string - 'null' description: The request field at fault, as a JSON path, or `null`. hint: type: - string - 'null' description: One concrete way to fix the request. details: type: object description: The numbers and values the message refers to, as fields. additionalProperties: true errors: type: array description: Every field error, when `code` is `invalid_fields`. Empty otherwise. items: $ref: '#/components/schemas/Error' retryable: type: boolean description: Whether the same request can succeed later, unchanged. retry_after: $ref: '#/components/schemas/Timestamp' description: When a retry can succeed, if known. doc_url: type: string format: uri Timestamp: type: string format: date-time description: >- RFC 3339 in UTC with milliseconds, for example `2026-09-27T14:30:00.123Z`. responses: Unauthorized: description: No valid API key. content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' examples: invalid_api_key: value: error: type: authentication code: invalid_api_key message: This API key is not valid. It may have been revoked. param: null hint: >- Send a current key as Authorization: Bearer tapi_…. Keys are created and revoked on the account page. details: {} errors: [] retryable: false doc_url: >- https://docs.tradingapi.dev/api-reference/errors#invalid_api_key RateLimited: description: >- The key made too many requests. Each key may make 10 requests at once, then 5 a second. Nothing was done; retry after `Retry-After` seconds. headers: Retry-After: description: The seconds to wait before retrying, always `1`. schema: type: string enum: - '1' content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' examples: rate_limited: value: error: type: rate_limited code: rate_limited message: This key made too many requests; retry in 1 s. param: null hint: >- Slow down: each key may make 10 requests at once, then 5 a second. details: {} errors: [] retryable: true retry_after: '2026-09-28T14:05:12.000Z' doc_url: >- https://docs.tradingapi.dev/api-reference/errors#rate_limited Unavailable: description: A service we depend on failed. Retry the same request. content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' examples: unavailable: value: error: type: unavailable code: unavailable message: The exchange could not be reached. param: null hint: >- Retry the same request with the same client_order_id; an order may already have been recorded. details: {} errors: [] retryable: true doc_url: https://docs.tradingapi.dev/api-reference/errors#unavailable securitySchemes: apiKey: type: http scheme: bearer bearerFormat: tapi_… description: >- An API key from the account page, sent as `Authorization: Bearer tapi_…`. ````