When creating custom landing pages on Fermion, you can include direct checkout links that seamlessly redirect users to purchase your digital products or courses. This allows you to maintain full control over your landing page design while still leveraging Fermion’s secure checkout system. Any anchor link or button with a redirect URL in the following format will open the Fermion checkout page: 
/api/buy-digital-product?product-slug=YOUR_PRODUCT_SLUG
The checkout page is automatically generated by Fermion and includes all necessary payment processing, security measures, and user authentication.

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URL Parameters

Fermion’s checkout system supports several URL parameters to customize the checkout experience:

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Required Parameters

  • product-slug: The slug of your digital product or course that you want users to purchase. This field is mandatory and cannot be omitted.

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Optional Parameters

  • discount-code: Any discount code that needs to be automatically applied to the user’s checkout session. The discount code must exist in your product’s discounts section area. If the code doesn’t exist or has expired, users will see an “Invalid discount code” warning but can still complete checkout at full price.
  • digital-product-price-id: The specific price ID for the digital product, useful if you have multiple pricing plans.
  • total-installments-count: The number of installments for partial payment plans. Only required if the selected plan is an installment plan.
  • prefilled-name: Pre-fills the user’s name on the checkout form. Useful when your landing page collects user input.
  • prefilled-email: Pre-fills the user’s email address on the checkout form. Useful when your landing page collects user input.
  • prefilled-phone-number: Pre-fills the user’s phone number on the checkout form. Useful when your landing page collects user input.
  • smart-checkout-redirect: Set to true to automatically redirect to the best available payment gateway when prefilled-email and prefilled-name are present. This reduces one step for users to complete.
  • UTM Parameters: For marketing attribution, you can add any of the following:
  • utm_source, utm_medium, utm_campaign, utm_id, utm_term, utm_content
Make sure to properly encode all parameter values to avoid breaking the checkout flow. Special characters in names, emails, or discount codes must be URL-encoded.

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Code Examples

<a href="/api/buy-digital-product?product-slug=my-awesome-product">
	Buy My Product
</a>

<a
	href="/api/buy-digital-product?product-slug=my-awesome-product&discount-code=EARLY_LAUNCH&utm_source=newsletter&utm_medium=email"
>
	Buy with Early Bird Discount
</a>

<a
	href="/api/buy-digital-product?product-slug=my-awesome-product&digital-product-price-id=price_123&total-installments-count=3&prefilled-name=John%20Doe&prefilled-email=john@example.com"
>
	Buy Product (3 Installments)
</a>

<a
	href="/api/buy-digital-product?product-slug=my-awesome-product&digital-product-price-id=price_123&total-installments-count=3&discount-code=EARLY_LAUNCH&prefilled-name=John%20Doe&prefilled-email=john@example.com&prefilled-phone-number=1234567890&smart-checkout-redirect=true&utm_source=adwords&utm_medium=cpc&utm_campaign=summer_sale"
>
	Buy Product Now
</a>

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JavaScript Implementation

For dynamic checkout links that collect user input from your landing page, use this JavaScript function to safely construct the checkout URL: 
function initiateCheckout() {
	// Assuming this function is called on a button click
	const params = new URLSearchParams({
		'discount-code': code,
		'product-slug': checkoutPageDataInfo.fermionDigitalProductSlug,
		'digital-product-price-id':
			checkoutPageDataInfo.pricingPlanSpecificData
				.fermionDigitalProductPriceId,
		'total-installments-count':
			checkoutPageDataInfo.pricingPlanSpecificData.planType ===
			'PartialPaymentPlan'
				? (
						checkoutPageDataInfo.pricingPlanSpecificData
							.installmentCountSelectedByUser ?? ''
				  ).toString()
				: '',
		'prefilled-name': nameOfUser || '',
		'prefilled-email': emailOfUser || '',
		'prefilled-phone-number': phoneNumber || '',
		'smart-checkout-redirect': 'true',
		utm_source: utmSource || '',
		utm_medium: utmMedium || '',
		utm_campaign: utmCampaign || '',
		utm_id: utmId || '',
		utm_term: utmTerm || '',
		utm_content: utmContent || '',
	})

	// Remove empty parameters
	params.forEach((value, key) => {
		if (value === '') params.delete(key)
	})

	window.location.href = `/api/buy-digital-product?${params.toString()}`
}
The JavaScript approach using URLSearchParams automatically handles URL encoding, making it the safest way to construct checkout links with user input.

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Manual URL Construction

If you prefer to construct URLs manually, ensure you use encodeURIComponent() for all parameter values: 
const productSlug = 'my-awesome-product'
const priceId = 'price_123'
const installmentCount = '3'
const userName = 'John Doe'
const userEmail = 'john@example.com'
const utmSource = 'newsletter'

const checkoutUrl = `/api/buy-digital-product?product-slug=${encodeURIComponent(
	productSlug
)}&digital-product-price-id=${encodeURIComponent(
	priceId
)}&total-installments-count=${encodeURIComponent(
	installmentCount
)}&prefilled-name=${encodeURIComponent(
	userName
)}&prefilled-email=${encodeURIComponent(
	userEmail
)}&utm_source=${encodeURIComponent(utmSource)}`
Failing to properly encode parameter values can break the checkout flow, especially when dealing with special characters in names, emails, or discount codes.

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Integration with Custom Landing Pages

To integrate checkout links with your custom landing pages:
  1. Create your custom page in Fermion’s instructor dashboard
  2. Design your landing page with HTML, CSS, and JavaScript
  3. Add checkout buttons/links using the /api/buy-digital-product URL format
  4. Test the checkout flow to ensure all parameters work correctly
  5. Publish your page when ready
Your custom landing page will maintain full design control while seamlessly integrating with Fermion’s secure checkout system.

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Best Practices

  • Always test checkout links before publishing your landing page
  • Use the JavaScript approach when collecting user input to ensure proper encoding
  • Keep discount codes simple and avoid special characters when possible
  • Validate user input before constructing checkout URLs
  • Provide fallback options in case discount codes are invalid or expired
  • Use UTM parameters to track marketing attribution and campaign performance
The checkout page automatically handles payment processing, user authentication, and product access management, so you can focus on creating compelling landing pages that drive conversions.