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

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

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

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

Installation

TypeScript (v2.4.0)

# 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 (v1.10.1)

pip install t402

# Or with uv
uv add t402

# CLI tool included
t402 --help

Go (v1.9.0)

go get github.com/t402-io/t402/sdks/go@v1.9.0

# CLI tool
go install github.com/t402-io/t402/sdks/go/cmd/t402@v1.9.0
t402 --help

Java (v1.10.0)

<dependency>
  <groupId>io.t402</groupId>
  <artifactId>t402</artifactId>
  <version>1.10.0</version>
</dependency>

Or with Gradle:

implementation 'io.t402:t402:1.10.0'

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: 44+ across 10 blockchain families

Latest Releases

SDK	Version	Release Date	Changelog
TypeScript	v2.4.0	2026-02-06	CHANGELOG
Python	v1.10.1	2026-02-06	CHANGELOG
Go	v1.9.0	2026-02-06	CHANGELOG
Java	v1.10.0	2026-02-06	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 1,222 Commits
.github		.github
.vscode		.vscode
contracts		contracts
e2e		e2e
examples		examples
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
DEVELOPMENT_PLAN_2026.md		DEVELOPMENT_PLAN_2026.md
LICENSE		LICENSE
NOTICE		NOTICE
README.md		README.md
RELEASING.md		RELEASING.md
ROADMAP.md		ROADMAP.md
SECURITY.md		SECURITY.md
SUPPORT.md		SUPPORT.md
codecov.yml		codecov.yml
package.json		package.json
pnpm-lock.yaml		pnpm-lock.yaml

License

t402-io/t402

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t402

Package Architecture

TypeScript (v2.4.0)

Python (v1.10.1)

Go (v1.9.0)

Java (v1.10.0)

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

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