Testing a REST-API Connection

Install a REST-API client

Install a client to send test requests to the REST API.

Recommended: Postman (free)

Alternative tools: cURL (command-line), Insomnia

curl -X GET "https://api.example.com/v1/data" \
  -H "Authorization: Bearer YOUR_TOKEN" \
  -H "Content-Type: application/json"

Gather connection details

Before connecting, make sure you have the following details:

API Reference/Documentation Obtain the official REST API documentation (webpage or document).

Request/Load Limitations Check for any restrictions, e.g., 100 requests/hour.

Connection Details

Endpoint Address: IP address and TCP port.

Credentials (examples below):

Basic Auth: Username & Password

Identifier & Secret

Bearer Token

OAuth2 Credentials:

Client ID & Client Secret, or Base64 token (identifier:secret encoded)

Username & Password

OAuth Scope (if non-default) – defines granted privileges

Custom Authentication: May require development effort.

Perform a request and get a 200 status code with data in return

Open your REST-API client and create a new request.

Set method & endpoint:

Select GET (or the method required by the API).

Enter the full enpoint.

Example: https://api.example.com/data

Authentication:

Go to the related authentication tab.

Select the required auth type (Basic Auth, Bearer Token etc.).

Enter your credentials or token.

Headers (if needed):

Add Content-Type: application/json or any required custom headers.

TLS validation:

Enter the TLS settings.

Disable validate certificate in your REST-API client if there are no valid TLS certificate served by the REST API (self-signed TLS certificate = invalid).

Perform a test request.

Expect an HTTP 200 OK response.

Verify that the response body contains the data you intend to collect.

Troubleshooting API connection

Permission denied or 401 Unauthorized

Could be caused by invalid credentials (expired token, wrong username/password).

Double-check credentials (token, username/password, client ID, client secret etc.).

Re-issue or refresh authentication tokens if expired.

Consult the API documentation for required parameters.

Couldn't resolve host name

Check the host name.

If DNS is used check if VPN is required to have access.

Test network reachibility: ping or curl to the endpoint.

Rate limits exceeded (too many requests in a short time)

Consult the API documentation for required parameters.