Online license activation

CommunityTeamsEnterprise (Online)

1. Requirements

Diffblue Cover requires a remote license check with the Diffblue licensing server each time it is used. Offline license activation is available with the Enterprise Edition offline option only.

To perform the license check Diffblue Cover needs an active internet connection to the following servers:


The license check uses this connection to identify individual devices. Further details regarding the exact data exchanged are available in the Privacy Notice.

2. Activating Diffblue Cover IntelliJ Plugin Online

3. Activating Diffblue Cover CLI Online

4. Configuring Diffblue Cover IntelliJ Plugin to use a proxy server

Please ensure you have the Proxy Server details configured in the IntelliJ settings page and then restart IntelliJ:

  • Windows and Linux: File | Settings | Appearance and Behavior | System Settings | HTTP Proxy
  • macOS: IntelliJ IDEA | Preferences | Appearance and Behavior | System Settings | HTTP Proxy

Please also see the HTTPS certificate errors information below.

5. Configuring Diffblue Cover CLI to use a proxy server

Diffblue Cover CLI utilizes the system Java proxy configurations; these can be set via the environment variable JVM_ARGS which details the proxy server FQDN and port, for example:

JVM_ARGS=" -Dhttps.proxyPort=8080"

As shown in this example:

Reminder: Ensure that the environment variable JVM_ARGS is set permanently according to your operating system instructions.

6. Troubleshooting license server connections

  1. Check you have an active internet connection at all times when using Diffblue Cover.
  2. Ensure you can access via a web browser; you will automatically receive a confirmation message when this is successful.
  3. Ensure you can access via a web browser, you should see the message “Welcome to the LicenseSpring API”.
  4. Ensure that any Proxy Server settings are correctly set up (see the bottom of this page).
  5. Please speak to your network manager about whitelisting the URLs above, and checking that port 443 is open.
  6. For the Diffblue Cover IntelliJ Plugin, restart IntelliJ.
  7. Try temporarily disabling anti-virus, malware detector or any firewall software.
  8. A detailed logfile is available which shows further diagnostic information about the license check process - please review the logs:

For further help troubleshooting licensing network connection issues, please contact Diffblue Support

7. Troubleshooting HTTPS certificate errors

If you have a proxy server that rewrites HTTPS connections and packages them with its own certificate, you may get an L018 output code. The simplest way to fix this is to disable certificate checks. You can do this by setting either the Java system property dcover.disable.ssl.license.cert.check or the environment variable DCOVER_DISABLE_SSL_LICENSE_CERT_CHECK to true. In IntelliJ you can add system properties using Help -> Edit custom properties.... This will open a file to which you should add a line such as:


When using Cover CLI the following environment variable can be configured:


Reminder: Ensure that the environment variable DCOVER_DISABLE_SSL_LICENSE_CERT_CHECK is set permanently according to your operating system instructions.