Pass API Key in Query String with cURL

This guide demonstrates how to pass an API key as a query parameter using the cURL command-line tool. You will learn the basic syntax for appending credentials to a URL, how to handle multiple query parameters, and important security considerations associated with this method of authentication.

Basic Syntax

To pass an API key in a query string, append a question mark (?) to the end of your target URL, followed by the API key parameter name, an equals sign (=), and your actual API key value.

Always wrap the entire URL in double quotes to prevent your command line shell from misinterpreting special characters.

curl "https://api.example.com/v1/data?api_key=your_actual_api_key_here"

Passing Multiple Parameters

If the API endpoint requires additional query parameters alongside the API key, use an ampersand (&) to separate each key-value pair.

curl "https://api.example.com/v1/users?api_key=your_actual_api_key_here&limit=10&status=active"

Handling Special Characters

If your API key or any of the query parameters contain special characters (such as spaces, hashes, or ampersands), they must be URL-encoded. You can instruct cURL to perform this encoding automatically using the --data-urlencode flag combined with the -G (or --get) flag, which forces cURL to send the data as a query string rather than a POST request.

curl -G "https://api.example.com/v1/data" --data-urlencode "api_key=your_api_key" --data-urlencode "query=search term"

Security Considerations

While passing API keys via query parameters is simple, it is generally less secure than using HTTP headers. Query parameters are often recorded in:

If the API supports it, consider passing your credentials in an authorization header instead:

curl -H "Authorization: Bearer your_actual_api_key_here" "https://api.example.com/v1/data"