# 31400: Bad Request

Log Level: ERROR

## Description

This error means Twilio could not understand the request because the syntax was malformed. 31400 is a Voice error with the message Bad Request.

### Possible causes

* The request body or parameters are malformed, so Twilio cannot parse the request.
* The request uses an unsupported content type instead of `application/x-www-form-urlencoded` or `multipart/form-data`.
* If you are using `device.connect()`, the `params` value is not a JavaScript object of key/value pairs, or the call data you send does not match what the Voice SDK expects.

### Possible solutions

* Rebuild the request with valid syntax and include every required field before you send it.
* Send Twilio API requests with a supported content type.
* If you are using `device.connect()`, pass `params` as a JavaScript object of key/value pairs, and keep the total length within 800 bytes.

#### Additional resources

* [Twilio API requests](/docs/usage/requests-to-twilio)
* [Voice SDK Error Codes](/docs/voice/sdks/error-codes)