# HTTP status code: 400 Bad Request

Independent and unofficial. Not affiliated with or endorsed by any broker or platform named here. Educational only: nothing here is advice, and nothing here recommends a broker or a trade.

This is the markdown version of https://openbrokerapi.com/errors/http/400, written from the same records as that page.

Risk warning: CFDs and spread bets are complex instruments and come with a high risk of losing money rapidly due to leverage. You can lose money on these products, and each provider publishes its own loss figure under FCA rules. You should consider whether you understand how they work and whether you can afford to take the high risk of losing your money. Automated and API trading can amplify losses through bugs, connectivity failures and runaway orders.

As text you can copy:

```
400 Bad Request
```

- Kind: Status code
- Read from: [RFC 9110, HTTP Semantics, section 15.5.1](https://www.rfc-editor.org/rfc/rfc9110.html#section-15.5.1)
- Status: verified. Source: [rfc-editor.org](https://www.rfc-editor.org/rfc/rfc9110.html#section-15.5.1), checked 2026-10-09.

## What does 400 Bad Request mean in HTTP?

The server cannot or will not process the request because it sees a fault on the client's side, such as malformed syntax or invalid message framing.

## What it means in trading API work

A trading API usually sends 400 when a field is missing, misspelt or out of range: a size below the minimum, a price with too many decimal places, an instrument name it does not know. The body of the reply normally carries the API's own error code, and that code is what names the fault.

This part is this site's own explanation, written for people learning to call a trading API. It is not part of the source cited above and it describes no particular broker.

## What should I do about 400 Bad Request?

Read the body of the reply and look up the API's own code. Compare what you sent with the documented request. Do not send the same request again unchanged, because it will be refused in the same way.

This page is an independent explanation in plain words. The definition itself is in [the source it was read from](https://www.rfc-editor.org/rfc/rfc9110.html#section-15.5.1), which is the authority if the two ever differ.

## Where to go next

- [Everything decoded for HTTP](https://openbrokerapi.com/errors/http)
- [Getting started with API trading](https://openbrokerapi.com/guides/getting-started-with-api-trading): What an API is, what you need and how to make a first call safely.
- [Brokers](https://openbrokerapi.com/brokers): The record for each broker: access, limits, endpoints and error codes.
- [Platform APIs](https://openbrokerapi.com/platforms): APIs that belong to trading software offered by many brokers.
- [Error codes](https://openbrokerapi.com/errors): What each error means, and the fix where the source gives one.

## Licence and how to cite

The records behind this page are all rights reserved. This file is the page itself, at its own address, in another format. It is not part of the CC BY 4.0 downloads listed at https://openbrokerapi.com/data. Quote from it with a link to the page.

Cite as: HTTP status code: 400 Bad Request. Broker API Hub, https://openbrokerapi.com/errors/http/400, newest check 2026-10-09.

Where you rely on a single figure, cite the source and the checked date printed beside it as well. Where this page and a broker's own documentation differ, the documentation wins.