Quickstart

From zero to a paid API in 60 seconds.

▶ Watch the 402 flow first

Interactive terminal demo — see request → 402 → Lightning pay → 200 OK, live in your browser.

Option A — Scaffold a full server in one command (fastest)

npx create-l402-app my-api

This creates a complete Express + l402-kit project: server.ts, .env.example, tsconfig.json, and a /premium endpoint ready to accept Lightning payments.

my-api/
  src/server.ts      ← your API with l402 middleware
  .env.example       ← Blink/OpenNode credentials template
  package.json       ← npm install l402-kit + tsx
  tsconfig.json
  README.md

Then:

cd my-api
cp .env.example .env   # add your Blink API key
npm install
npm run dev
# ⚡ l402-kit server running on http://localhost:3000
# curl http://localhost:3000/premium  →  402 Payment Required

---

Option B — Add to an existing project

1. Choose your mode

	Managed ⭐	Soberano
Setup time	~2 min	~5 min
Monthly cost	$0	$0
Per-transaction fee	0.3%	0%
What you need	A Lightning address	A Blink / Alby / BTCPay account
Processing 10,000 sats	30 sat fee	$0 fee
Best for	Getting started fast	Volume / production

Not sure? Start with Managed — no node, no account, just a Lightning address. Switch to Soberano in one line of code whenever you want 0% fees. Already-paid tokens keep working after the switch.

Get a Lightning address (free, 2 min): Sign up at dashboard.blink.sv — you’ll receive [e-mail]. Or use Alby, Phoenix, or Wallet of Satoshi.

Soberano setup: Sign up at dashboard.blink.sv → API Keys → create key → copy your BTC Wallet ID from the wallet page. Set BLINK_API_KEY and BLINK_WALLET_ID in your .env.

2. Install

TypeScript

npm install l402-kit

pip install l402kit

go get github.com/shinydapps/l402-kit/go

cargo add l402kit

3. Add to your API

Managed (⭐ Recommended)

No Lightning node needed — just your Lightning address.

Express

import express from "express";
import { l402, ManagedProvider } from "l402-kit";

const app = express();
const lightning = ManagedProvider.fromAddress("[e-mail]");

app.get("/premium", l402({ priceSats: 100, lightning }), (_req, res) => {
  res.json({ data: "You paid 100 sats. Here is your data." });
});

app.listen(3000);
// 0.3% fee · no node setup · works immediately

from fastapi import FastAPI, Request
from l402kit import l402_required, ManagedProvider

app = FastAPI()
lightning = ManagedProvider.from_address("[e-mail]")

@app.get("/premium")
@l402_required(price_sats=100, lightning=lightning)
async def premium(request: Request):
    return {"data": "You paid 100 sats. Here is your data."}

package main

import (
    "fmt"
    "net/http"
    l402kit "github.com/shinydapps/l402-kit/go"
)

func main() {
    provider := l402kit.NewManagedProvider("[e-mail]")
    http.Handle("/premium", l402kit.Middleware(l402kit.Options{
        PriceSats: 100,
        Lightning: provider,
    }, http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        fmt.Fprintln(w, `{"data":"You paid 100 sats. Here is your data."}`)
    })))
    http.ListenAndServe(":8080", nil)
}

use axum::{middleware, routing::get, Router};
use l402kit::{l402_middleware, Options, ManagedProvider};
use std::sync::Arc;

#[tokio::main]
async fn main() {
    let provider = ManagedProvider::new("[e-mail]".into());
    let opts = Arc::new(Options::new(100, provider));
    let app = Router::new()
        .route("/premium", get(|| async { r#"{"data":"You paid 100 sats. Here is your data."}"# }))
        .route_layer(middleware::from_fn_with_state(opts, l402_middleware));
    let listener = tokio::net::TcpListener::bind("0.0.0.0:8080").await.unwrap();
    axum::serve(listener, app).await.unwrap();
}

Soberano (0% fee — Blink)

Your own Lightning wallet. Sign up at dashboard.blink.sv and copy your API Key + BTC Wallet ID.

Express

import express from "express";
import { l402, BlinkProvider } from "l402-kit";

const app = express();
const lightning = new BlinkProvider(
  process.env.BLINK_API_KEY!,
  process.env.BLINK_WALLET_ID!,
);

app.get("/premium", l402({ priceSats: 100, lightning }), (_req, res) => {
  res.json({ data: "You paid 100 sats. Here is your data." });
});

app.listen(3000);

import os
from fastapi import FastAPI, Request
from l402kit import l402_required, BlinkProvider

app = FastAPI()
lightning = BlinkProvider(
    api_key=os.environ["BLINK_API_KEY"],
    wallet_id=os.environ["BLINK_WALLET_ID"],
)

@app.get("/premium")
@l402_required(price_sats=100, lightning=lightning)
async def premium(request: Request):
    return {"data": "You paid 100 sats. Here is your data."}

package main

import (
    "fmt"
    "net/http"
    "os"
    l402kit "github.com/shinydapps/l402-kit/go"
)

func main() {
    blink := l402kit.NewBlinkProvider(os.Getenv("BLINK_API_KEY"), os.Getenv("BLINK_WALLET_ID"))
    http.Handle("/premium", l402kit.Middleware(l402kit.Options{
        PriceSats: 100,
        Lightning: blink,
    }, http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        fmt.Fprintln(w, `{"data": "You paid 100 sats. Here is your data."}`)
    })))
    http.ListenAndServe(":8080", nil)
}

use axum::{middleware, routing::get, Router};
use l402kit::{l402_middleware, Options, BlinkProvider};
use std::sync::Arc;

#[tokio::main]
async fn main() {
    let provider = BlinkProvider::new(
        std::env::var("BLINK_API_KEY").unwrap(),
        std::env::var("BLINK_WALLET_ID").unwrap(),
    );
    let opts = Arc::new(Options::new(100, provider));
    let app = Router::new()
        .route("/premium", get(|| async { r#"{"data":"You paid 100 sats. Here is your data."}"# }))
        .route_layer(middleware::from_fn_with_state(opts, l402_middleware));
    let listener = tokio::net::TcpListener::bind("0.0.0.0:8080").await.unwrap();
    axum::serve(listener, app).await.unwrap();
}

4. Test it

curl http://localhost:3000/premium

Response:

{
  "error": "Payment Required",
  "price_sats": 100,
  "invoice": "lnbc1u1p...",
  "macaroon": "eyJoYXNo..."
}

Pay the invoice with any Lightning wallet, then:

curl http://localhost:3000/premium \
  -H "Authorization: L402 <macaroon>:<preimage>"

Response:

{ "data": "You paid 100 sats. Here is your data." }

Your API now accepts Bitcoin payments.

---

Test without real sats

You don’t need a Lightning wallet to test your integration. Use a mock provider — it generates valid cryptographic token pairs locally, zero network calls:

import { createHash, randomBytes } from "crypto";
import { l402 } from "l402-kit";
import type { LightningProvider, Invoice } from "l402-kit";

// Drop-in mock — generates real SHA256 hash/preimage pairs
function makeMockProvider(): LightningProvider & { preimage: string } {
  const preimage = randomBytes(32).toString("hex");
  const paymentHash = createHash("sha256").update(Buffer.from(preimage, "hex")).digest("hex");
  return {
    preimage, // use this in your test Authorization header
    async createInvoice(amountSats: number): Promise<Invoice> {
      const macaroon = Buffer.from(
        JSON.stringify({ hash: paymentHash, exp: Date.now() + 3_600_000 })
      ).toString("base64");
      return { paymentRequest: "lnbc_mock", paymentHash, macaroon, amountSats };
    },
    async checkPayment(): Promise<boolean> { return true; },
  };
}

// Usage in tests:
const mock = makeMockProvider();
app.get("/premium", l402({ priceSats: 10, lightning: mock }), handler);

// Step 1 — unauthenticated → 402
const res402 = await request(app).get("/premium");
// res402.body.macaroon  ← use this

// Step 2 — pay with mock preimage → 200
const res200 = await request(app)
  .get("/premium")
  .set("Authorization", `L402 ${res402.body.macaroon}:${mock.preimage}`);
// res200.status === 200 ✓

For real-money testing with the sandbox, use OpenNode’s testMode:

const lightning = new OpenNodeProvider(process.env.OPENNODE_KEY!, true); // testMode: no real sats

Full testing guide → Testing