Payment Required

x402 can't complete a payment without Coinbase. L402 can't be stopped by anyone. Both protocols want to define how AI agents pay for APIs.

x402

Coinbase required. Dollar-stable, zero gas. Verification and settlement go through a Facilitator.

Agent

Server

Facilitator

1 Agent → Server GET /premium-data

2 Server → Agent 402 + PAYMENT-REQUIRED

{ "x402Version": 1, "accepts": [{ "scheme": "exact", "network": "base", "maxAmountRequired": "10000", "resource": "/premium-data", "payTo": "0x742d...0bEb", "asset": "0x8335...2913", "maxTimeoutSeconds": 60 }] }

3 Agent (local) Sign EIP-3009 auth

4 Agent → Server Retry + PAYMENT-SIGNATURE

X-PAYMENT: base64({ "signature": "0xab12...f9", "authorization": { "from": "0x3a1B...c7", "to": "0x742d...0bEb", "value": "10000", "validBefore": 1741363260 } })

Single-use EIP-3009 transferWithAuthorization payload. Signature is verified by the Facilitator.

5 Server → Facilitator POST /verify

Facilitator Verification

Coinbase validates signature
Checks balance & allowance
Holds funds for settlement

Verifying...

6 Facilitator → Server Verified (~100ms)

7 Server → Agent 200 OK + resource

8 Facilitator → Chain transferWithAuthorization

9 Chain → Facilitator Confirmed (~2s)

Done

Verification and settlement require Coinbase's Facilitator

L402

No intermediary. Agent pays, server verifies locally. Every step runs between the two counterparties.

Agent

Server

Lightning

1 Agent → Server GET /premium-data

2 Server → Agent 402 + WWW-Authenticate: L402

WWW-Authenticate: L402 macaroon="AGIAJEemVQ...Cg==", invoice="lnbc100n1p3..."

Macaroon contains payment_hash as caveat. Invoice is standard BOLT-11.

3 Agent → Lightning Pay invoice → preimage

4 Agent → Server Authorization: L402 mac:preimage

Authorization: L402 macaroon="AGIAJEemVQ...Cg==", preimage="b3f5a1c8...9d2e"

Macaroon is reusable. Preimage proves payment — SHA256(preimage) matches the invoice's payment_hash caveat.

5 Server → Agent 200 OK + resource

Done

0 of 5 steps need permission

	x402	L402
Trust model	Facilitator required	No intermediary
Verification	Remote (Facilitator API)	Local (HMAC + SHA256)
Privacy	On-chain visible	Off-chain, onion-routed
Credential	Single-use signature	Reusable macaroon
Currency	USDC (stablecoin)	Bitcoin (sats, volatile)
Client gas	None (facilitator pays)	N/A
Settlement	~2s (Base L2)	~1-2s (Lightning)
Multi-chain	Yes (Base, Solana, fiat)	Lightning only
Challenge	`PAYMENT-REQUIRED`	`WWW-Authenticate: L402`
Payment header	`X-PAYMENT`	`Authorization: L402`
Backed by	Coinbase, Cloudflare, Google, Visa	Lightning Labs
Since	May 2025	March 2020

HTTP 402 Payment Required has been "reserved for future use" since 1997. Two protocols now claim that future. They've made opposite bets on whether payments need an intermediary.

x402 requires a Facilitator—Coinbase's infrastructure—to verify signatures and settle funds on-chain. The agent never touches gas and gets dollar-stable pricing. If the Facilitator rejects the request or goes down, the payment doesn't complete.

L402 has no intermediary. Agent pays a Lightning invoice, server verifies a hash locally, resource delivered. Zero steps require anyone's permission. You run Lightning infrastructure, price in volatile sats, and channel liquidity is your problem.

An AI agent making thousands of API calls a day will eventually need to pay for one. Whether it can depends on who else has to be involved.

Text description of protocol comparison

x402 Protocol (9 steps)

Client sends GET request to Server
Server returns 402 Payment Required with PAYMENT-REQUIRED header containing JSON payment terms
Client signs an EIP-3009 gasless authorization off-chain (no gas, no transaction)
Client retries request with PAYMENT-SIGNATURE header containing the signed proof
Server sends the signed payload to the Facilitator for verification
Facilitator verifies the signature off-chain (~100ms) and confirms
Server delivers the resource (200 OK) — before on-chain settlement
Facilitator submits transferWithAuthorization to settle USDC on Base (~2s)
Blockchain confirms the on-chain settlement

L402 Protocol (5 steps)

Client sends GET request to Server
Server returns 402 with WWW-Authenticate header containing a macaroon and Lightning invoice
Client pays the Lightning invoice with any wallet, receiving the preimage as proof
Client retries request with Authorization header containing the macaroon and preimage
Server verifies locally (SHA256 of preimage matches payment_hash in macaroon) and delivers the resource

Sideband · Data sourced from x402 and L402 protocol specs · CC BY 4.0