x402 vs AP2: Stablecoin Rail vs Agent Payment Authorization

Short answer: x402 and AP2 sit at different layers and were designed to work together. x402, from Coinbase (6 May 2025, Apache 2.0), is an HTTP-native settlement rail: it revives the HTTP 402 status code so an agent can pay for an API, content or a service in stablecoins, with on-chain settlement through a facilitator. AP2, the Agent Payments Protocol from Google (16 September 2025), is a payment-agnostic authorization framework: it proves a user authorized an agent to spend, across cards, bank transfers or stablecoins. The two compose rather than compete: AP2 extends to crypto through the A2A x402 extension, which Google built with Coinbase. Use x402 to move stablecoins, use AP2 to authorize the spend.

Criterion	x402	AP2
Author / steward	Coinbase, now the x402 Foundation	Google (60+ orgs)
Announced	6 May 2025	16 Sep 2025
Open-source status	Open source, Apache 2.0	Open specification (public GitHub)
What it is	HTTP-native payment rail	Agent payment-authorization framework
Payment type	On-chain stablecoins via facilitators (EIP-3009)	Payment-agnostic (cards, stablecoins, bank transfers)
Transport	HTTP 402 status code; MCP and A2A representations	Extension of A2A and MCP
Primary use	Pay per request for APIs, content and services	Prove a user authorized an agent to spend
How they relate	AP2 settles crypto via the A2A x402 extension	Uses x402 as its crypto settlement rail
Notable adoption	AWS, Cloudflare, Circle, Coinbase	Mastercard, PayPal, American Express, Adyen, Coinbase

Criterion

x402

AP2

Author / steward

Coinbase, now the x402 Foundation

Google (60+ orgs)

Announced

6 May 2025

16 Sep 2025

Open-source status

Open source, Apache 2.0

Open specification (public GitHub)

What it is

HTTP-native payment rail

Agent payment-authorization framework

Payment type

On-chain stablecoins via facilitators (EIP-3009)

Payment-agnostic (cards, stablecoins, bank transfers)

Transport

HTTP 402 status code; MCP and A2A representations

Extension of A2A and MCP

Primary use

Pay per request for APIs, content and services

Prove a user authorized an agent to spend

How they relate

AP2 settles crypto via the A2A x402 extension

Uses x402 as its crypto settlement rail

Notable adoption

AWS, Cloudflare, Circle, Coinbase

Mastercard, PayPal, American Express, Adyen, Coinbase

Frequently asked questions

Is x402 the same as AP2?

No. x402 is a settlement rail for stablecoin payments over HTTP, AP2 is an authorization framework. AP2 can use x402 as its crypto rail.

Which should an agent developer use?

They are complementary. Use x402 to move stablecoins per request, and AP2 to carry proof that the user authorized the payment. AP2’s crypto extension is built on x402.

Are both open?

x402 is Apache 2.0, stewarded by the x402 Foundation. AP2 publishes an open specification led by Google with 60+ organizations.