This varies from product to product, but using these guidelines can help to prevent any accidental purchases of incompatible software!
In most cases. DLC content only works if it shares the same platform as the base game.
Check the product information page for your game.
If your base game is purchased on another client, such as Steam, Origin, or Uplay, and the product page has the matching requirement on Direct2Drive, they should be compatible.
For example : DLC content which requires a steam account on its product page on Direct2Drive.com would work with a base game bought on steam. Since the end up on the same platform.
If your game is a retail box copy, in most cases it will not be compatible with Digitally Purchased DLC
Digital copies of games tend to use different activation systems then store bought, there are a few exceptions to this, but it is best to assume that they will not be compatible.
Games which require steam to be installed to run, even when store bought ( like Civilization V ) can still be compatible with online purchases, as long as they meet the requirements above. ( The DLC platform requirement matches the one your base game is on )
Support is always happy to answer questions related to games you want to purchase.
Compatibility questions are always confusing ones, and we want to make sure you are confident in your purchase. Support is always available to take your questions and will answer you as quickly as possible.
We're happy to help. You can contact us HERE!