> ## Documentation Index > Fetch the complete documentation index at: https://docs.elapse.finance/llms.txt > Use this file to discover all available pages before exploring further. # Introduction > Elapse is Stripe Billing for things that should charge by the second. A subscriber starts a meter, watches a live dollar counter tick, cancels whenever they like, and pays only the seconds that elapsed. Your server finds out through a signed webhook, not a cron job. ```json subscription.canceled theme={"system"} { "id": "evt_test_subscription_canceled", "object": "event", "type": "subscription.canceled", "created": 1757160000, "livemode": false, "pending_webhooks": 1, "data": { "object": { "id": "sub_test00000000000", "object": "subscription", "status": "canceled", "product": "prod_test0000000000", "customer": "cus_test00000000000", "checkout_session": "cs_test000000000000", "manage_url": "https://elapse.finance/account", "rate_usd_per_second": "0.004", "started_at": 1757159917, "paused_at": null, "canceled_at": 1757160000, "ended_reason": "canceled", "max_duration_seconds": 3600, "max_escrow_usd": "14.4", "funded_usd": "14.4", "settled_usd": "0.332", "seconds_elapsed": 83, "currency": "ausd", "livemode": false, "created": 1757159910, "amount_settled": "0.332" } } } ``` That body arrives at your endpoint when someone cancels. `seconds_elapsed` and `amount_settled` are cumulative for the subscription, so one handler call tells you what was used and what was paid. ## Why per second Usage is continuous. Billing never was, because card networks and slow chains made anything finer than a month uneconomic. GPU hours, API calls, live streams and seats are all metered by the second in your own logs and then rounded up to a month on the invoice. Elapse runs on Monad, where blocks land every few hundred milliseconds and fees are near zero. That makes a per-second meter honest: accrual happens continuously on a contract, the counter your subscriber sees is `rate × seconds`, and settlement is batched so nobody pays gas per tick. Subscribers never see any of that. They see Face ID, dollars and seconds. ## Three surfaces **Platform API.** Products, Checkout sessions, Subscriptions, Customers, Invoices and Events, with the ids and conventions you already know from Stripe: `prod_`, `cus_`, `sub_`, `evt_`, bearer secret keys, `snake_case` JSON, cursor pagination. The [API reference](/api-reference/authentication) is generated from the same schemas the server validates with. **`@elapse/react`.** You create a session and render `` and `` in your own page. Elapse handles sign-in, the permit and the live meter in a window it opens on its own origin, so the subscriber never leaves your app and you never hold a card or a wallet. **Webhooks.** Six lifecycle events, signed with `X-Elapse-Signature`, retried on a fixed schedule, verified with one SDK call. There are no per-second events. ## Where to start Install the SDK, create a Product, take a Checkout URL to your phone and receive one webhook. About ten minutes. Every event, when it fires, and what your server should do with it. The ten methods in `@elapse/sdk`, with a cURL twin for each, and the React components beside them. Addresses and events for anyone who wants to check the chain.