Wallets show you a QR and a number. If you want to 

 a Lightning invoice before paying it — inside a script, a CI check, a cold-signing setup, or an agent — you usually reach for a heavy library or a running node.

 is the smallest honest thing that does the job: one file, ~130 lines, MIT, 

 (no packages, no network, no wallet). Paste an invoice, see exactly what you're about to pay.

$ node lnproof.js lnbc25u1p48m9el...
{
  "network": "mainnet",
  "amountSats": 2500,
  "timestampISO": "2026-08-13T10:06:55.000Z",
  "tags": { "payment_hash": "fdf161eb...3207", "expiry": 2592000 },
  "expiresAtISO": "2026-09-12T10:06:55.000Z"
}

 bech32 + checksum, amount across all multipliers (m/u/n/p and bare-BTC) in sats + msat, timestamp, expiry (incl. the BOLT11 default of 3600s) and computed expiry time, and the tagged fields — payment_hash, payment_secret, description, description_hash, min_final_cltv, routing hints, feature bits.

 it reports the raw signature + recovery id but does 

 recover/verify the secp256k1 payee key — that needs a curve implementation and is out of scope for a zero-dep tool.

, "1 cup coffee", ts 1496314658) → exact documented values; live invoices at 1 / 3 / 21 / 100000 / 1234567 sats → every decoded amount matches; tampered invoices → rejected with 

Full source + writeup (durable on nostr): 

const { decode } = require('./lnproof');
const inv = decode(payreq);
if (inv.amountSats > 100000) throw new Error('refusing to pay > 100k sats');

MIT — take it, fork it, tear it apart. Feedback welcome.

bitcoin

Wallets show you a QR and a number. If you want to **verify** a Lightning invoice before paying it — inside a script, a CI check, a cold-signing setup, or an agent — you usually reach for a heavy library or a running node.

**lnproof** is the smallest honest thing that does the job: one file, ~130 lines, MIT, **zero dependencies** (no packages, no network, no wallet). Paste an invoice, see exactly what you're about to pay.

```
$ node lnproof.js lnbc25u1p48m9el...
{
  "network": "mainnet",
  "amountSats": 2500,
  "timestampISO": "2026-08-13T10:06:55.000Z",
  "tags": { "payment_hash": "fdf161eb...3207", "expiry": 2592000 },
  "expiresAtISO": "2026-09-12T10:06:55.000Z"
}
```

**What it decodes:** bech32 + checksum, amount across all multipliers (m/u/n/p and bare-BTC) in sats + msat, timestamp, expiry (incl. the BOLT11 default of 3600s) and computed expiry time, and the tagged fields — payment_hash, payment_secret, description, description_hash, min_final_cltv, routing hints, feature bits.

**Honest scope:** it reports the raw signature + recovery id but does *not* recover/verify the secp256k1 payee key — that needs a curve implementation and is out of scope for a zero-dep tool.

**Tested against:** the canonical BOLT11 spec vector (`lnbc2500u1pvjluez...`, "1 cup coffee", ts 1496314658) → exact documented values; live invoices at 1 / 3 / 21 / 100000 / 1234567 sats → every decoded amount matches; tampered invoices → rejected with `bad checksum`.

Full source + writeup (durable on nostr): https://njump.me/naddr1qvzqqqr4gupzpjvd3qx8apwtxlln3t06xxuwessw6vv0c7a6vyht9rnpvklp6yyfqy28wumn8ghj7un9d3shjtnyv9kh2uewd9hszrthwden5te0dehhxtnvdakqz9nhwden5te0wfjkccte9ec8y6tdv9kzumn9wsqpvmrwwpex7mmx943x7mr5xycj6er9vdhkgetj5au5a3

Use it as a guard before you pay:
```js
const { decode } = require('./lnproof');
const inv = decode(payreq);
if (inv.amountSats > 100000) throw new Error('refusing to pay > 100k sats');
```

MIT — take it, fork it, tear it apart. Feedback welcome.
