t402

t402 is an open standard for internet native payments. It aims to support all networks (both crypto & fiat) and forms of value (stablecoins, tokens, fiat).

app.use(
  paymentMiddleware(
    {
      "GET /weather": {
        accepts: [...],                 // As many networks / schemes as you want to support
        description: "Weather data",    // what your endpoint does
      },
    },
  ),
);
// That's it! See examples/ for full details

Package Architecture

@t402/core              Core types, client, server, facilitator abstractions
@t402/extensions        Bazaar, Sign-In-With-X extensions

Mechanisms (Chain-specific payment implementations):
@t402/evm               EIP-3009, ERC-4337, USDT0 bridge for EVM chains (19 networks)
@t402/evm-core          Shared EVM utilities
@t402/svm               Solana SPL token support
@t402/ton               TON Jetton (TEP-74) support
@t402/tron              TRON TRC-20 support
@t402/near              NEAR NEP-141 token support
@t402/aptos             Aptos Fungible Asset support
@t402/tezos             Tezos FA2 token support
@t402/polkadot          Polkadot Asset Hub support
@t402/stacks            Stacks (Bitcoin L2) SIP-010 support
@t402/cosmos            Cosmos (Noble) native USDT support
@t402/erc8004           ERC-8004 Trustless Agents (identity, reputation)

HTTP Integrations:
@t402/express           Express.js middleware
@t402/hono              Hono middleware
@t402/fastify           Fastify middleware
@t402/next              Next.js integration
@t402/fetch             Fetch API wrapper
@t402/axios             Axios interceptor
@t402/paywall           Payment wall UI components
@t402/react             React hooks and components
@t402/vue               Vue composables and components

WDK (Wallet Development Kit):
@t402/wdk               Tether WDK integration
@t402/wdk-gasless       ERC-4337 gasless payments
@t402/wdk-bridge        LayerZero cross-chain bridging
@t402/wdk-multisig      Safe multi-sig support
@t402/wdk-ton           TON wallet management
@t402/wdk-ton-gasless   Gasless TON transactions via relay
@t402/wdk-tron-gasfree  Gas-free TRON USDT transfers
@t402/wdk-defi          DeFi pre-payment processor (swap, borrow, bridge-swap)
@t402/wdk-protocol      High-level T402Protocol (auto balance + bridge + pay)

Transports:
@t402/a2a               Agent-to-Agent transport

Mobile:
@t402/react-native      React Native SDK with PaymentSheet

Mechanisms (Additional):
@t402/btc               Bitcoin (PSBT on-chain + Lightning BOLT11)

Tools:
@t402/mcp               AI Agent MCP server (Claude, etc.)
@t402/cli               Command-line tools

Installation

TypeScript (v2.7.1)

# Core packages
pnpm add @t402/core @t402/evm

# With specific framework
pnpm add @t402/express  # Express.js
pnpm add @t402/next     # Next.js
pnpm add @t402/hono     # Hono

# Gasless payments
pnpm add @t402/wdk-gasless

# MCP Server for AI Agents
pnpm add @t402/mcp
npx @t402/mcp  # Run directly

# CLI tool
pnpm add -g @t402/cli
t402 --help

Python (v1.12.1)

pip install t402

# Or with uv
uv add t402

# CLI tool included
t402 --help

Go (v1.12.1)

go get github.com/t402-io/t402/sdks/go@v1.12.1

# CLI tool
go install github.com/t402-io/t402/sdks/go/cmd/t402@v1.12.1
t402 --help

Java (v1.12.1)

<dependency>
  <groupId>io.t402</groupId>
  <artifactId>t402</artifactId>
  <version>1.12.1</version>
</dependency>

Or with Gradle:

implementation 'io.t402:t402:1.12.1'

Supported Networks

EVM (Ethereum Virtual Machine) - 19 USDT0 Networks

Ethereum (eip155:1), Arbitrum (eip155:42161), Optimism (eip155:10)
Base (eip155:8453), Polygon (eip155:137), Ink (eip155:57073)
Berachain (eip155:80094), Unichain (eip155:130), Mantle (eip155:5000)
Sei (eip155:1329), Conflux (eip155:1030), Monad (eip155:143)
Flare (eip155:14), Rootstock (eip155:30), XLayer (eip155:196)
Plasma (eip155:9745), HyperEVM (eip155:999), MegaETH (eip155:4326)
Corn (eip155:21000000)
Legacy USDT: BNB Chain, Avalanche, Fantom, Celo, Kaia

ERC-4337 Account Abstraction

Gasless Transactions: Users pay zero gas fees via paymaster sponsorship
Smart Accounts: Safe 4337 Module v0.3.0 integration
Bundlers: Pimlico, Alchemy, and generic bundler support
Paymasters: Pimlico, Biconomy, Stackup integrations
EntryPoint v0.7: Full support for latest ERC-4337 specification

SVM (Solana Virtual Machine)

Solana Mainnet (solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp)
Solana Devnet (solana:EtWTRABZaYq6iMfeYKouRu166VU2xqa1)
Supports USDC and native SOL

TON (The Open Network)

TON Mainnet (ton:mainnet)
TON Testnet (ton:testnet)
Supports USDT Jetton (TEP-74 standard)

TRON

TRON Mainnet (tron:mainnet)
TRON Nile Testnet (tron:nile)
TRON Shasta Testnet (tron:shasta)
Supports USDT TRC-20 (TIP-20 standard)

NEAR Protocol

NEAR Mainnet (near:mainnet)
NEAR Testnet (near:testnet)
Supports USDT NEP-141 token

Aptos

Aptos Mainnet (aptos:1)
Aptos Testnet (aptos:2)
Supports USDT Fungible Asset

Tezos

Tezos Mainnet (tezos:NetXdQprcVkpaWU)
Tezos Ghostnet (tezos:NetXnHfVqm9iesp)
Supports USDt FA2 token

Polkadot

Polkadot Asset Hub (polkadot:68d56f15f85d3136970ec16946040bc1)
Westend Asset Hub (testnet)
Supports USDT (Asset ID: 1984)

Stacks (Bitcoin L2)

Stacks Mainnet (stacks:1)
Stacks Testnet (stacks:2147483648)
Supports sBTC and SIP-010 tokens

Cosmos (Noble)

Noble Mainnet (cosmos:noble-1)
Noble Testnet (cosmos:grand-1)
Supports native USDC via MsgSend

USDT0 Cross-Chain Bridge (LayerZero)

All 19 USDT0 networks fully supported
Message tracking via LayerZero Scan API

CLI Tools

All SDKs include CLI tools for payment operations.

# Verify a payment payload
t402 verify <base64-payload>

# Settle a payment
t402 settle <base64-payload>

# List supported networks
t402 supported

# Encode/decode payloads
t402 encode payment.json
t402 decode <base64-string>

# Network information
t402 info eip155:8453

Available in: TypeScript (@t402/cli), Python (pip install t402), Go (go install .../cmd/t402)

Principles

Open standard: the t402 protocol will never force reliance on a single party
HTTP Native: t402 is meant to seamlessly complement the existing HTTP request made by traditional web services
Chain and token agnostic: we welcome contributions that add support for new chains, signing standards, or schemes
Trust minimizing: all payment schemes must not allow for the facilitator or resource server to move funds, other than in accordance with client intentions
Easy to use: t402 needs to be 10x better than existing ways to pay on the internet

SDK Feature Matrix

Feature	TypeScript	Go	Python	Java
Core Client	✅	✅	✅	✅
Core Server	✅	✅	✅	✅
Facilitator	✅	✅	✅	✅
EVM (19 USDT0 networks)	✅	✅	✅	✅
SVM (Solana)	✅	✅	✅	✅
TON	✅	✅	✅	✅
TRON	✅	✅	✅	✅
NEAR	✅	✅	✅	✅
Aptos	✅	✅	✅	✅
Tezos	✅	✅	✅	✅
Polkadot	✅	✅	✅	✅
Stacks	✅	✅	✅	✅
Cosmos	✅	✅	✅	✅
ERC-4337 Gasless	✅	✅	✅	✅
USDT0 Bridge	✅	✅	✅	✅
WDK Integration	✅	✅	✅	✅
MCP Server	✅	✅	✅	✅
CLI Tool	✅	✅	✅	✅

Legend: ✅ Complete | ❌ Not Available

Total Supported Networks: 50 across 10 blockchain families (81 network+scheme kinds)

Latest Releases

SDK	Version	Release Date	Changelog
TypeScript	v2.7.1	2026-02-23	CHANGELOG
Go	v1.12.1	2026-02-23	CHANGELOG
Python	v1.12.1	2026-02-23	CHANGELOG
Java	v1.12.1	2026-02-23	CHANGELOG

Ecosystem

The t402 ecosystem is growing! Check out our ecosystem page to see projects building with t402.

Whitepaper: T402 Protocol Whitepaper (PDF)
Roadmap: ROADMAP.md
Documentation: docs.t402.io

Terms

resource: Something on the internet (webpage, API, RPC service, etc.)
client: An entity wanting to pay for a resource
facilitator: A server that facilitates verification and execution of payments
resource server: An HTTP server that provides an API or resource for a client

Typical t402 Flow

sequenceDiagram
    participant Client
    participant Server as Resource Server
    participant Facilitator
    participant Blockchain

    Client->>Server: GET /api
    Server->>Client: 402 Payment Required
    Note over Client: Create payment payload
    Client->>Server: GET /api + PAYMENT-SIGNATURE header
    Server->>Facilitator: POST /verify
    Facilitator->>Server: Verification result
    Note over Server: Process request
    Server->>Facilitator: POST /settle
    Facilitator->>Blockchain: Submit transaction
    Blockchain->>Facilitator: Confirmed
    Facilitator->>Server: Settlement result
    Server->>Client: 200 OK + Content

Client makes an HTTP request to a resource server
Resource server responds with 402 Payment Required and PAYMENT-REQUIRED header
Client creates a PaymentPayload based on selected scheme & network
Client sends request with PAYMENT-SIGNATURE header
Resource server verifies via facilitator's /verify endpoint
Facilitator validates and returns verification response
If valid, server fulfills request and settles payment via /settle
Resource server returns 200 OK with PAYMENT-RESPONSE header

Quick Start Examples

TypeScript Client

import { t402Client, wrapFetchWithPayment } from "@t402/fetch";
import { registerExactEvmScheme } from "@t402/evm/exact/client";
import { privateKeyToAccount } from "viem/accounts";

const client = new t402Client();

registerExactEvmScheme(client, {
  signer: privateKeyToAccount(process.env.PRIVATE_KEY as `0x${string}`),
});

const fetchWithPayment = wrapFetchWithPayment(fetch, client);
const response = await fetchWithPayment("https://api.example.com/data");

TypeScript Server (Express)

import express from "express";
import { paymentMiddleware, t402ResourceServer } from "@t402/express";
import { ExactEvmScheme } from "@t402/evm/exact/server";

const app = express();

app.use(
  paymentMiddleware(
    {
      "GET /api/data": {
        accepts: [
          { scheme: "exact", price: "$0.01", network: "eip155:8453", payTo: "0x..." },
        ],
        description: "Premium API data",
      },
    },
    new t402ResourceServer(facilitatorClient)
      .register("eip155:8453", new ExactEvmScheme()),
  ),
);

Python Server (Flask)

from flask import Flask
from t402.flask import create_paywall

app = Flask(__name__)

paywall = create_paywall(
    routes={
        "GET /api/data": {
            "price": "$0.01",
            "network": "eip155:8453",
            "pay_to": "0x...",
            "description": "Premium API data",
        },
    },
    facilitator_url="https://facilitator.t402.io",
)
app.register_blueprint(paywall)

@app.route("/api/data")
def get_data():
    return {"data": "premium content"}

Go Server

package main

import (
    "net/http"
    t402 "github.com/t402-io/t402/sdks/go"
    t402http "github.com/t402-io/t402/sdks/go/http"
)

func main() {
    server := t402.NewResourceServer(facilitatorClient)

    mux := http.NewServeMux()
    mux.Handle("/api/data", t402http.PaymentMiddleware(
        server,
        t402http.RouteConfig{
            Path: "GET /api/data",
            Accepts: []t402.PaymentRequirement{
                {Scheme: "exact", Price: "$0.01", Network: "eip155:8453", PayTo: "0x..."},
            },
        },
        http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
            w.Write([]byte(`{"data": "premium content"}`))
        }),
    ))

    http.ListenAndServe(":8080", mux)
}

ERC-4337 Gasless Payments

import { SafeSmartAccount, createBundlerClient, createPaymaster } from "@t402/evm/erc4337";

// Create Safe smart account
const safeAccount = new SafeSmartAccount({
  owner: privateKeyToAccount(ownerPrivateKey),
  chainId: 8453,
});

// Connect bundler and paymaster
const bundler = createBundlerClient({ provider: "pimlico", apiKey, chainId: 8453 });
const paymaster = createPaymaster({ provider: "pimlico", apiKey, chainId: 8453 });

// Build, sponsor, and submit UserOperation
const callData = safeAccount.encodeExecute(targetAddress, 0n, data);
const userOp = await bundler.buildUserOperation({ sender: smartAccountAddress, callData });
const paymasterData = await paymaster.sponsorUserOperation(userOp);
const hash = await bundler.sendUserOperation({ ...userOp, ...paymasterData, signature });

MCP Server for AI Agents

# Install and run
npx @t402/mcp

# Claude Desktop config (~/.config/claude/claude_desktop_config.json)
{
  "mcpServers": {
    "t402": {
      "command": "npx",
      "args": ["@t402/mcp"],
      "env": { "T402_DEMO_MODE": "true" }
    }
  }
}

Available Tools:

t402/getBalance - Check wallet balance
t402/getAllBalances - Check all chain balances
t402/pay - Execute payment
t402/payGasless - Gasless payment via ERC-4337
t402/getBridgeFee - Get bridge fee quote
t402/bridge - Bridge USDT0 between chains

USDT0 Cross-Chain Bridge

import { Usdt0Bridge, LayerZeroScanClient } from "@t402/evm";

const bridge = new Usdt0Bridge(signer, "arbitrum");

// Get quote
const quote = await bridge.quote({
  fromChain: "arbitrum",
  toChain: "ethereum",
  amount: 100_000000n,
  recipient: "0x...",
});

// Execute bridge
const result = await bridge.send({ ...quote });

// Track delivery
const scanClient = new LayerZeroScanClient();
await scanClient.waitForDelivery(result.messageGuid);

Specification

See specs/ for full documentation of the t402 standard.

Schemes

A scheme is a logical way of moving money. Different schemes support different payment flows:

exact - Transfer a specific amount (e.g., pay $1 to read an article)
upto - Transfer up to an amount based on usage (e.g., LLM token generation)

See specs/schemes/ for detailed scheme specifications.

Contributing

See CONTRIBUTING.md for development setup and guidelines.

Security

See SECURITY.md for security policy and vulnerability reporting.

License

Apache 2.0 - See LICENSE for details.

Name		Name	Last commit message	Last commit date
Latest commit History 1,480 Commits
.github		.github
.vscode		.vscode
contracts		contracts
e2e		e2e
ecosystem		ecosystem
examples		examples
premium @ 2c6f956		premium @ 2c6f956
sdks		sdks
services		services
specs		specs
whitepaper		whitepaper
.dockerignore		.dockerignore
.gitignore		.gitignore
.gitmodules		.gitmodules
CHANGELOG.md		CHANGELOG.md
CODEOWNERS		CODEOWNERS
CODE_OF_CONDUCT.md		CODE_OF_CONDUCT.md
CONTRIBUTING.md		CONTRIBUTING.md
LICENSE		LICENSE
NOTICE		NOTICE
README.md		README.md
RELEASING.md		RELEASING.md
SECURITY.md		SECURITY.md
SUPPORT.md		SUPPORT.md
codecov.yml		codecov.yml
llms-full.txt		llms-full.txt
llms.txt		llms.txt
package.json		package.json
pnpm-lock.yaml		pnpm-lock.yaml

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t402

Package Architecture

TypeScript (v2.7.1)

Python (v1.12.1)

Go (v1.12.1)

Java (v1.12.1)

EVM (Ethereum Virtual Machine) - 19 USDT0 Networks

ERC-4337 Account Abstraction

SVM (Solana Virtual Machine)

TON (The Open Network)

TRON

NEAR Protocol

Aptos

Tezos

Polkadot

Stacks (Bitcoin L2)

Cosmos (Noble)

USDT0 Cross-Chain Bridge (LayerZero)

CLI Tools

Principles

SDK Feature Matrix

Latest Releases

Ecosystem

Terms

Typical t402 Flow

Quick Start Examples

Specification

Schemes

Contributing

Security

License

About

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