How to authenticate with a bearer token in cURL

Bearer tokens let cURL send an issued access credential to an API without repeating a password or browser session on every request. This fits OAuth 2.0 access tokens, service-account calls, and repeatable CLI checks against protected endpoints.

In cURL, the dedicated option for this job is --oauth2-bearer. It formats the standard Authorization: Bearer header for the request and keeps the command shorter than building that header manually each time.

Bearer tokens remain reusable secrets until they expire or are revoked. Keep them out of shared shell history, verbose logs, and tickets, and be especially careful with --location or other redirect-following flows because the credential should only reach the host that is meant to receive it.

Steps to authenticate with a bearer token in cURL:

Set the bearer token in the current shell before making the request.
```
$ ACCESS_TOKEN='eyJ...sig-redacted'
```
Replace the masked value with the real issued token in actual use, and prefer an existing restricted secret source when the workflow already has one.
Send the request with --oauth2-bearer and confirm that the API accepts the credential.
```
$ curl --silent --show-error \
--oauth2-bearer "$ACCESS_TOKEN" \
--write-out '\nHTTP %{http_code}\n' \
https://httpbin.org/bearer
{
  "authenticated": true
}

HTTP 200
```
The same option works with a real protected endpoint; success is the authenticated response plus the API's documented success status.
Inspect the echoed headers when the server says the token was missing or malformed.
```
$ curl --silent --show-error \
--oauth2-bearer "$ACCESS_TOKEN" \
https://httpbin.org/headers
{
  "headers": {
    "Authorization": "Bearer eyJ...sig-redacted"
  }
}
```
The Authorization line proves that cURL sent the bearer token in the standard header format before the request reached the application.

Related: How to view HTTP request headers with cURL
Repeat the call without the token when the protection boundary itself needs confirmation.
```
$ curl --silent --show-error \
--write-out '\nHTTP %{http_code}\n' \
https://httpbin.org/bearer

HTTP 401
```
A clear 401 Unauthorized confirms that the endpoint is enforcing bearer authentication instead of succeeding for unrelated reasons.
Clear the token from the current shell after the request batch finishes.
```
$ unset ACCESS_TOKEN
```
The variable disappears only from the current shell, so any copied logs, saved config files, or recordings still need separate cleanup.