I'm designing a public API to my company's data. We want application developers to sign up for an API key so that we can monitor use and overuse.
Since the API is REST, my initial thought is to put this key in a custom header. This is how I've seen Google, Amazon, and Yahoo do it. My boss, on the other hand, thinks the API is easier to use if the key becomes merely a part of the URL, etc. "http://api.domain.tld/longapikey1234/resource". I guess there is something to be said for that, but it violates the principle of the URL as a simple address of what you want, and not how or why you want it.
Would you find it logical to put the key in the URL? Or would you rather not have to manually set HTTP headers if writing a simple javascript frontend to some data?
It should be put in the HTTP Authorization header. The spec is here https://tools.ietf.org/html/rfc7235
If you want an argument that might appeal to a boss: Think about what a URL is. URLs are public. People copy and paste them. They share them, they put them on advertisements. Nothing prevents someone (knowingly or not) from mailing that URL around for other people to use. If your API key is in that URL, everybody has it.
It is better to use API Key in header, not in URL.
URLs are saved in browser's history if it is tried from browser. It is very rare scenario. But problem comes when the backend server logs all URLs. It might expose the API key.
In two ways, you can use API Key in header
Basic Authorization:
Example from stripe:
curl https://api.stripe.com/v1/charges -u sk_test_BQokikJOvBiI2HlWgH4olfQ2:
curl uses the -u flag to pass basic auth credentials (adding a colon after your API key will prevent it from asking you for a password).
Custom Header
curl -H "X-API-KEY: 6fa741de1bdd1d91830ba" https://api.mydomain.com/v1/users
I would not put the key in the url, as it does violate this loose 'standard' that is REST. However, if you did, I would place it in the 'user' portion of the url.
eg: http://me@example.com/myresource/myid
This way it can also be passed as headers with basic-auth.
passing api key in parameters makes it difficult for clients to keep their APIkeys secret, they tend to leak keys on a regular basis. A better approach is to pass it in header of request url.you can set user-key header in your code . For testing your request Url you can use Postman app in google chrome by setting user-key header to your api-key.
来源：https://stackoverflow.com/questions/5517281/place-api-key-in-headers-or-url