Hey @Rishabh20! Glad to see you here in the Klaviyo community.
Klaviyo does have a fairly robust API that you can use to integrate your app with Klaviyo. There’s a whole developer portal with documentation and guides to get you acquainted with Klaviyo’s data model, architecture and sample code for authentication and a list of various API endpoints you can use.
You can see there here:
Also, depending on where you want to connect to Klaviyo (from the server side, or at the client edge, or both) and your back end programming stack, there’s a few officially supported SDKs here that can get you started quickly (wraps the REST endpoints) for you.
On the client side, in Klaviyo’s Github repository, you can find both an IOS Swift SDK as well as an early pre-alpha version of the Android SDK here though they haven’t been updated in a while, but might help you get started:
Finally, join us over at the Klaviyo Developer Group here in the community if you run into any issues or need further help.