Curl With Headers

A “curl request header” is an HTTP header that can be used in an HTTP request to provide additional context and metadata, so that the server can tailor the way it processes the request and sends a response.

The short answer

To set a single header when sending a request with curl, you can use the -H or --header flag as follows:

$ curl -H "<header>" URL

Where <header> is an HTTP header composed of a name and a value in the following format: name: value. For example: "Content-Type: plain/text".

curl with multiple headers at once

To pass multiple headers at once with curl, you can simply repeat the -H flag for each header you want to add to the HTTP request as follows:

$ curl -H "<header1>" -H "<header2>" URL

Easily retrieve this command using Warp’s AI Command Search

If you’re using Warp as your terminal, you can easily retrieve this command using the Warp AI Command Search feature:

Entering curl send headers json token in the AI Command Search will prompt a curl command that includes the Content-Type and the Authorization headers, which can then quickly be inserted into your shell by doing CMD+ENTER.

Examples of common use cases for curl headers

Here are a few examples of commonly used HTTP headers when sending requests with curl.

Sending authenticated requests

Since many APIs require requests to be authenticated, to access protected data or perform sensitive operations, you can use the Authorization header to send your credentials alongside with the request itself.

Here is an example of a curl GET request with an authorization header:

$ curl -H "Authorization: Bearer <token>" 
  https://api.example.com/user/profile

You can also read our other articles if you want to learn more about sending authentication headers and performing basic authentication with curl.

Specifying the payload encoding of the request

Another common use case for sending headers with curl is to specify the encoding of the payload contained in the request. This is useful when sending data in a specific format such as JSON or URL-encoded, to indicate to the server which parsing method to use.

Here is an example of a curl POST request with a content-type header:

$ curl -X POST -H "Content-Type: application/json" 
  -d '{"city":"paris"}' https://api.weather.com/forecast

Specifying client requirements for the response

Here's a more complex example with multiple headers used to indicate to the server how it should format its response before sending it back to the client.

$ curl -H "Accept: application/json" -H "Accept-Language: en-US" 
  -H "Cache-Control: max-age=3600" https://api.example.com

Where:

• The "Accept" header indicates that the response should be in the JSON format.
• The "Accept-Language" header indicates that the response should be in American English.
• The "Cache-Control" header indicates that the response should not be older than 3600 seconds (i.e. 1 hour).