# Knowledge Base

Short answers to the questions CryptAPI users ask most. If you can't find what you need, [contact us](https://cryptapi.io/contacts).

## FAQs

- [Do I need an API Key?](/kb/faq/do-i-need-an-api-key)
- [Do I need to register my website?](/kb/faq/do-i-need-to-register-my-website)
- [Do you save any transaction data?](/kb/faq/do-you-save-any-transaction-data)
- [How do I get payment notifications by email?](/kb/faq/how-do-i-get-payment-notifications-by-email)
- [How long is a generated address valid?](/kb/faq/how-long-the-generated-address-is-valid-for)
- [How much are your transaction fees?](/kb/faq/how-much-are-your-transaction-fees)
- [I think I got billed more than needed, why?](/kb/faq/i-think-i-got-billed-more-than-needed-why)

## Developers

- [Where and how to start?](/kb/developers/where-and-how-to-start)
- [How does CryptAPI work?](/kb/developers/how-it-works)
- [How to easily test CryptAPI](/kb/developers/how-to-easily-test-cryptapi)
- [How to verify the callback signature](/kb/developers/how-to-verify-the-callback-signature)
- [How does the value field in callbacks work?](/kb/developers/how-the-value-field-provided-in-the-callbacks-work)
- [How the multi_token parameter works](/kb/developers/how-the-multi_token-parameter-works)
- [How the priority parameter works](/kb/developers/how-the-priority-parameter-works)
- [Multi-Address Minimums](/kb/developers/multi-address-minimums)

## Plugins

- [WooCommerce](/kb/plugins/installing-and-configuring-woocommerce-plug-in)
- [Magento](/kb/plugins/installing-and-configuring-our-magento-extension)
- [OpenCart](/kb/plugins/installing-and-configuring-our-opencart-extension)
- [PrestaShop](/kb/plugins/installing-and-configuring-our-prestashop-module)