# WebSocket close code: 1003 Unsupported Data

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/websocket/1003, 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:

```
1003 Unsupported Data
```

- Kind: Close code
- Where you meet it: When a WebSocket connection closes
- Read from: [RFC 6455, The WebSocket Protocol, section 7.4.1; the name is as the IANA WebSocket Close Code Number Registry writes it](https://www.rfc-editor.org/rfc/rfc6455.html#section-7.4.1)
- Status: verified. Source: [rfc-editor.org](https://www.rfc-editor.org/rfc/rfc6455.html#section-7.4.1), checked 2026-10-09.

## What does 1003 Unsupported Data mean in WebSocket?

An endpoint is ending the connection because it received a type of data it cannot accept, for example binary data sent to an endpoint that understands only text.

## What it means in trading API work

The stream expects text messages and received binary, or the reverse.

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 1003 Unsupported Data?

Check whether the API documents text or binary messages, and send that type.

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/rfc6455.html#section-7.4.1), which is the authority if the two ever differ.

## Where to go next

- [Everything decoded for WebSocket](https://openbrokerapi.com/errors/websocket)
- [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: WebSocket close code: 1003 Unsupported Data. Broker API Hub, https://openbrokerapi.com/errors/websocket/1003, 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.