Log in to HDFC NetBanking or the HDFC MobileBanking app
Go to the Credit Cards section
Select your credit card
Open the Card Controls or Manage Card option
Enable Domestic Online Transactions
Enable International Online Transactions if needed
Set the transaction limit if required
Save or confirm the changes
If NetBanking or app access is unavailable, call HDFC customer care
You can also activate online transactions through HDFC ATMs if the option is available on your card
Wait for the activation confirmation before trying an online purchase