---
description: Supported header name and value formats for response header modifications.
title: Format of HTTP response header names and values
image: https://developers.cloudflare.com/og-docs.png
---

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# Format of HTTP response header names and values

Last updated Aug 24, 2026|Copy as Markdown|[View as Markdown](https://mchen-ai-models-sync.previews.developers.cloudflare.com/rules/transform/response-header-modification/reference/header-format/index.md)|[Agent setup](https://mchen-ai-models-sync.previews.developers.cloudflare.com/agent-setup/)

The **name** of the HTTP response header you want to set or remove can only contain:

* Alphanumeric characters: `a`\-`z`, `A`\-`Z`, and `0`\-`9`
* The following special characters: `-` and `_`

The **value** of the HTTP response header you want to set can only contain:

* Alphanumeric characters: `a`\-`z`, `A`\-`Z`, and `0`\-`9`
* The following special characters: `` _ :;.,\/"'?!(){}[]@<>=-+*#$&`|~^% ``

The **length** of the HTTP response header can be a maximum of 4 KB (\~4,096 characters).

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