> ## Documentation Index > Fetch the complete documentation index at: https://citicardactivationguide.mintlify.site/llms.txt > Use this file to discover all available pages before exploring further. # Citi Card Activation FAQ: Answers to Common Questions > Answers to common Citi card activation questions, like why activation is required, what happens if you don't activate, and how soon you can use your card. [Get Started Here →]() These are quick answers to the questions people ask most about activating a Citi® credit card. Each links to a full article where one exists. > **Why do I need to activate my credit card?** > > Activation is a security measure that helps prevent fraudulent charges if someone intercepts your card in the mail. > **What are the ways to activate my Citi card?** > > You can typically activate [online](/activate/online.md), [by phone](/activate/by-phone.md), or in the [Citi Mobile App](/activate/mobile-app.md). > **How soon can I use my card after activating?** > > Usually right away. There typically isn't a delay between activation and when you can use the card. > **What happens if I don't activate my card?** > > Your account stays open, but you generally can't make purchases. You're still responsible for applicable fees, such as an annual fee. If the account stays unused for a long time, it may be closed. > **What information do I need?** > > Your card details and personal information such as the last 4 digits of your SSN or your date of birth. See [Activation Quickstart](/quickstart.md). > **How can I tell if my card is already active?** > > Try activating it again or contact customer service. See [After Activation](/help/after-activation.md). > **Is this website run by Citi?** > > No. This is an independent guide. Always activate through official Citi channels such as [Citi.com/activate](https://www.citi.com/activate). This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.