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This middleware normalizes HTTP header names to their canonical format. Very useful if clients are not using the canonical names of header (e.g. content-type as opposed to Content-Type).

API Gateway does not perform any normalization, so the headers are propagated to Lambda exactly as they were sent by the client.

Other middlewares like jsonBodyParser or urlEncodeBodyParser will rely on headers to be in the canonical format, so if you want to support non-normalized headers in your app you have to use this middleware before those ones.

This middleware will copy the original headers in event.rawHeaders.


To install this middleware you can use NPM:

npm install --save @middy/http-header-normalizer


  • normalizeHeaderKey (function) (optional): a function that accepts an header name as a parameter and returns its canonical representation.
  • canonical (bool) (optional): if true, modifies the headers to canonical format, otherwise the headers are normalized to lowercase (default false)

Sample usage

import middy from '@middy/core'
import httpHeaderNormalizer from '@middy/http-header-normalizer'

const handler = middy((event, context) => {
return {}