Offer setup before anything syncs
Custom API receives cleaner data when the offer, product, price, checkout mode, invoice, and automation path are defined first.
App integrations
developer-tools
Connect Custom API to the platforms you already sell with
Use Plandalf to connect Custom API with checkout pages, payment flows, email tools, CRM records, access systems, tax engines, and webhooks.
Popular connections
Custom API works with…
Use these as practical recipes, not just directory entries. Each one should explain the checkout, automation, payment, email, CRM, tax, or API handoff that matters.
Custom API + PayPal
Score 85
Build custom PayPal checkout flows with Custom API and Plandalf webhooks.
Custom API + Stripe
Score 77
Build custom Stripe checkout flows with Custom API and Plandalf webhooks.
Custom API + Drip
Score 30
Use Custom API and Drip together in a Plandalf checkout and post-purchase workflow.
Custom API + Kit (ConvertKit)
Score 30
Use Custom API and Kit (ConvertKit) together in a Plandalf checkout and post-purchase workflow.
Custom API + Klaviyo
Score 30
Use Custom API and Klaviyo together in a Plandalf checkout and post-purchase workflow.
Custom API + Mailchimp
Score 30
Use Custom API and Mailchimp together in a Plandalf checkout and post-purchase workflow.
Custom API + Next.js
Score 30
Use Custom API and Next.js together in a Plandalf checkout and post-purchase workflow.
Custom API + Zapier
Score 30
Use Custom API and Zapier together in a Plandalf checkout and post-purchase workflow.
Custom API + Avalara
Score 27
Use Custom API and Avalara together in a Plandalf checkout and post-purchase workflow.
Custom API + TaxJar
Score 27
Use Custom API and TaxJar together in a Plandalf checkout and post-purchase workflow.
Custom API + HubSpot
Score 24
Use Custom API and HubSpot together in a Plandalf checkout and post-purchase workflow.
Custom API + Shopify
Score 24
Use Custom API and Shopify together in a Plandalf checkout and post-purchase workflow.
How it works
Plandalf is the commerce layer between apps
Custom API keeps doing what it is best at. Plandalf handles the offer, checkout, buyer fields, payment context, invoice data, and post-purchase events that every other app needs.
For teams that write their own code, Plandalf's enrolment catch URL is a plain HTTP endpoint you can call from anywhere — your own backend, a serverless function, a scheduled job, a webhook receiver. Not a third-party platform in the usual sense; it's a catalog entry because the Emails tab renders "here's how to enrol participants via your own code" the same way it renders Zapier or MailerLite instructions — one template, one code path, no special casing. ## What Plandalf does here - **Direct enrolment API** — the catch URL on each enrolment sequence accepts a simple JSON body with `email` and `ref`. No SDK required. - **Stable `ref`-keyed participants** — repeat POSTs with the same `ref` re-resolve an existing participant rather than creating duplicates.
Search paths
Pages this hub can feed
Product surfaces to check before wiring Custom API
A useful Custom API integration page should show where the operator configures Offers, payment options, invoices, Automations, integrations, and API settings before a developer ships the flow.
Checkout can live on the site or app
Custom API can launch a hosted checkout, buy button, embedded flow, or SDK checkout depending on where the buyer starts.
Recipes to keep open while building
Custom API can be part of a payment stack, a site stack, a marketing stack, or an automation stack. These Plandalf resources keep the implementation tied to real checkout and purchase events.
Checkout completed fulfilment Route product, buyer, invoice, and payment state after purchase. Purchase event webhook fanout Send one purchase event into multiple downstream tools. API-first commerce stack Use SDK checkout, API keys, webhooks, and operator-visible settings together. Custom API platform overview See the supported roles, setup patterns, and product surfaces for Custom API.