L402

How to use it as an API

Understanding L402: Pay-Per-Use APIs with Bitcoin 💡

L402 is a "Bitcoin Standard" for APIs. It lets different applications "talk" to each other securely. Instead of usernames, passwords, and credit card details, it uses a clever combination of:

  • Macaroons: These are like special, tamper-proof digital "tickets" or "tokens" that grant access.
  • Lightning Network: This allows for instant, low-fee Bitcoin payments.

Together, they create a secure and private way to access paid services. You only pay for what you use.Learn More

Choose a service to get started:

ImageText GenerationSMS

How to Use Our L402 Services: A Step-by-Step Guide ⚙️

Using an L402-protected service involves a simple two-step process: first, you request access and get a "bill" (invoice), and second, you pay the bill and present your "proof of payment" (preimage) to use the service.

Step 1: Request Access & Get Your "Ticket" and "Invoice"

  1. Make Your First Request: Send your initial API request to the desired service endpoint.
  2. Receive a 402 Payment Required Response: This is normal! The response header will contain:
    • A Macaroon (your access "ticket").
    • An Invoice (a Lightning Network payment request).
    www-authenticate: L402 macaroon="<YOUR_UNIQUE_MACAROON>", invoice="<LIGHTNING_INVOICE_STRING>"

Step 2: Pay the Invoice & Use the Service

  1. Pay the Lightning Invoice: Use any Lightning-compatible wallet.
  2. Get the Preimage: After payment, your wallet provides a preimage (your "proof of payment").
  3. Make Your Second Request (with Payment Proof): Send the exact same request as in Step 1 tohttps://sats4ai.com/api/l402/sms. This time, include the `Authorization` header:
    Authorization: L402 <YOUR_UNIQUE_MACAROON>:<YOUR_PREIMAGE>

❗ Important Notes:

  • Identical Requests: The body/data of your first and second requests must be exactly the same.
  • Not a Stream (Currently): Our L402 services do not currently support streaming responses.

Using the L402 SMS Sending API

You can send an SMS by sending a POST request to our L402-protected SMS endpoint. Follow the steps below, which include example `curl` commands.

API Endpoint: https://sats4ai.com/api/l402/sms

Step 1: Initial Request (to get Macaroon and Invoice)

First, make a request to the API with your desired SMS parameters (phone number and message). This initial request will not send the SMS yet; instead, it will return a 402 Payment Required status along with the L402 headers (a macaroon and a Lightning invoice).

Example `curl` command:

curl -X POST https://sats4ai.com/api/l402/sms \
-H "Content-Type: application/json" \
-d '{"phone_number":"+1234567890","message":"Hello, this is a test SMS!"}' \
-i

Explanation of the command:

  • -X POST: Specifies an HTTP POST request.
  • https://sats4ai.com/api/l402/sms: The target API URL for sending SMS.
  • -H "Content-Type: application/json": Indicates the request body is JSON.
  • -d '{...}': The JSON data payload with your SMS details (see "Request Body Parameters" below).
  • -i: Tells `curl` to include HTTP response headers in the output (so you can see the www-authenticate header).

Expected Response Headers:

You will receive an HTTP/1.1 402 Payment Required response. Look for the www-authenticate header:

www-authenticate: L402 macaroon="<YOUR_MACAROON_STRING_HERE>", invoice="<YOUR_LIGHTNING_INVOICE_HERE>"
  • <YOUR_MACAROON_STRING_HERE>: Your unique access token (the "ticket" for this specific SMS request).
  • <YOUR_LIGHTNING_INVOICE_HERE>: The Lightning Network invoice you need to pay to send the SMS.

Step 2: Pay the Lightning Invoice

Copy the <YOUR_LIGHTNING_INVOICE_HERE> string and pay it using any Lightning-enabled Bitcoin wallet. Upon successful payment, your wallet will provide you with a preimage. The preimage is your cryptographic proof of payment.

Step 3: Final Request (to Send the SMS)

Once you have the macaroon (from Step 1) and the preimage (from Step 2), make the exact same POST request again. This time, include an Authorization header containing both.

Important: The JSON data payload (-d '{...}') in this second request must be identical to the one sent in Step 1.

Example `curl` command:

curl -X POST https://sats4ai.com/api/l402/sms \
-H "Content-Type: application/json" \
-H "Authorization: L402 <YOUR_MACAROON_STRING_HERE>:<YOUR_PREIMAGE_HERE>" \
-d '{"phone_number":"+1234567890","message":"Hello, this is a test SMS!"}'

Explanation of changes:

  • Replace <YOUR_MACAROON_STRING_HERE> with the actual macaroon from Step 1.
  • Replace <YOUR_PREIMAGE_HERE> with the actual preimage from Step 2.
  • The -H "Authorization: L402 <macaroon>:<preimage>" header is added to authorize the SMS sending.

Expected Successful Response:

If the L402 authentication is valid, the API will process your request and attempt to send the SMS. You should receive a success response, typically a JSON object confirming the submission:

Okay

Note: The exact success response format may vary. Check the API provider's documentation for specific details.

Request Body Parameters

The POST request body should be a JSON object with the following structure:

{
  "phone_number": "+1234567890",
  "message": "Hello, this is a test SMS!"
}

phone_number: string

The recipient's phone number in E.164 international format.

Example: "+1234567890"

message: string

The content of the SMS text message.

Maximum length: 120 characters.

Example: "Hello, this is a test SMS!"