---
"@context": https://schema.org
"@type": TechArticle
"@id": https://www.twilio.com/docs/api/errors/13253#article
headline: "13253: Dial: Header is too long"
url: https://www.twilio.com/docs/api/errors/13253
inLanguage: en
dateModified: 2026-06-08T11:38:30.000Z
author:
  "@type": Organization
  name: Twilio Developer Education Team
publisher:
  "@type": Organization
  name: Twilio
---

# 13253: Dial: Header is too long

Log Level: WARNING

## Description

Twilio returns this warning when the SIP header data you send with `<Dial><Sip>` or in the `To` SIP URI is longer than the supported limit. Custom SIP headers are passed in the SIP URI, and the headers portion must be under 1024 characters.

### Possible causes

* A custom SIP header appended to the SIP URI is longer than the supported 1024-character limit.
* A header sent with `<Sip>` uses a supported custom or standard SIP header name, but its value is too large. Twilio supports custom headers with the `x-` prefix and also supports `User-to-User`, `Remote-Party-ID`, `P-Preferred-Identity`, and `P-Called-Party-ID` in this format.
* The SIP URI includes header data in the `To` parameter, and the combined header content exceeds the allowed length.

### Possible solutions

* Shorten the header data you append to the SIP URI so the headers portion stays under 1024 characters.
* Remove any unnecessary custom SIP headers and send only the headers your SIP endpoint requires. For custom headers, use the `x-` prefix unless you are sending one of the supported standard SIP headers.
* If you create the call through the REST API, review the `To` parameter and confirm it contains a valid SIP URI. Keep the SIP URI body under 255 characters and keep the header data within the supported header limit.

#### Additional resources

* [TwiML Voice: `<Sip>`](/docs/voice/twiml/sip)
* [Making SIP Calls](/docs/voice/api/sip-making-calls)
* [TwiML Voice: `<Dial>`](/docs/voice/twiml/dial)