WooCommerce
One WordPress plugin. The plan picker renders inside your theme's buy box with your fonts and colors — customers choose one-time or subscribe-and-save, and consent is captured verbatim at checkout.

The Subscribe & Save widget in your product page's buy box — it inherits your theme automatically.
What the plugin does
One-time purchase and every subscription frequency with its discount, priced live from the plans you configure in the dashboard.
The exact terms each customer agreed to are saved with their subscription — the records regulators ask for, kept without you thinking about it.
Every renewal creates a normal paid order in your store admin. Shipping, tax, and inventory keep working exactly as they do today.
No replaced checkout, no redirect to a funnel page. Payment capture stays with your gateway.
Upload the plugin, paste your API key from Settings, done. Works with any WooCommerce theme.
Choose which products offer which frequencies and discounts — multi-product plans included.
The widget appears on your product pages immediately. Test mode lets you run the whole loop first.