eSIM API Security: Protecting Your Balance, Keys and Customer Data
eSIM API security protects the prepaid balance that pays for every eSIM you order. Use scoped API keys, keep test and live keys separate, restrict live keys to your servers with an IP allowlist, turn on two-step sign-in, verify webhooks and give each team member the smallest role they need. Fully Signal provides all of these controls in the partner panel.
How to Sell eSIMs in Your Online Store: Shopify, WooCommerce and Custom Shops
To sell eSIM in your online store, list each destination plan as a product, then deliver the eSIM after payment — manually from a wholesale partner panel, through an automation tool, or automatically through a REST API. Fully Signal supports all three with white-label QR codes and install pages, a free sandbox and no commission.
eSIM API Error Handling and Idempotency: Never Double-Charge an Order
eSIM API idempotency means sending a unique key with every order so a retried request returns the original order instead of buying a second eSIM. Combine it with timeouts, clear handling of balance and catalogue errors, webhooks and daily reconciliation, and your integration will never double-charge a customer. Fully Signal's REST API supports idempotent orders and a free sandbox to test every case.
Sandbox Testing for eSIM APIs: Build Your Integration Before You Pay
An eSIM API sandbox lets you build and test orders, top-ups and refunds with test keys and a sample catalogue, without spending money or creating real eSIMs. Fully Signal's sandbox gives every partner a test key, a €1,000 test balance, sample destinations and prices, sample orders in every eSIM state, and scenarios for hard-to-reproduce outcomes.
eSIM Webhooks: Automating Order Status, Activation and Expiry
eSIM webhooks are HTTP callbacks that tell your system when something changes — an order completes, fails or is refunded, or an eSIM is activated or expires — so you don't have to poll the API. On Fully Signal each webhook is signed with HMAC-SHA256 in the X-FULLYSIGNAL-Signature header and retried automatically if your endpoint is down.
How to Integrate an eSIM API Into Your Website or App
To integrate an eSIM API, sync the catalogue into your product pages, create an order after your customer pays (with an idempotency key so retries never double-buy), show the returned install link or QR code, listen for webhooks, and add top-ups and refunds. Build it all in the sandbox first, then switch to live keys.
Best eSIM API for Developers and Platforms in 2026
The best eSIM API gives you a live catalogue, one-call ordering that returns a ready-to-install eSIM, top-ups, usage and refunds, webhooks for status changes, a full sandbox and solid security such as scoped keys and IP allowlists. Fully Signal's REST API covers all of these and returns a white-label install page with every eSIM.