---
"@context": https://schema.org
"@type": TechArticle
"@id": https://www.twilio.com/docs/api/errors/40000#article
headline: "40000: Content-Type of 'application/json' not set"
url: https://www.twilio.com/docs/api/errors/40000
inLanguage: en
dateModified: 2026-03-11T20:01:16.000Z
author:
  "@type": Organization
  name: Twilio Developer Education Team
publisher:
  "@type": Organization
  name: Twilio
---

# 40000: Content-Type of 'application/json' not set

Log Type: APPLICATION

Log Level: ERROR

## Description

### Possible causes

* You responded with a 200 HTTP response but did not provide a `Content-Type` header of 'application/json'

### Possible solutions

* Add `Content-Type` header of 'application/json'

### Example

```json
{
	"instruction": "accept"
}
```

with no `Content-Type` header provided.