Pricing Experiments with x402: A/B Testing Micropayments Without New Infra

x402 lets you A/B test price points for paid APIs and content with per-request stablecoin payments over plain HTTP—often by adding a small proxy or one middleware line. This guide shows concrete patterns, code, and guardrails to run live pricing experiments in days, not months. (github.com)

Summary

x402 is an open HTTP-native payment protocol created by Coinbase that uses the 402 Payment Required status to negotiate per-request payments with clients (humans or AI agents). It supports “exact” payments on Base and Solana via USDC today. (github.com)
You can stand up A/B price tests without refactoring your origin API by using an edge proxy (Cloudflare Workers), a gateway, or a thin middleware that returns x402-compliant 402 challenges and verifies “paid” retries. (developers.cloudflare.com)

Why x402 is ideal for pricing experiments right now

Programmatic, per-request charges: No accounts, sessions, or API keys—clients get a 402 with machine-readable payment requirements, pay, then retry with a signed X-PAYMENT header. That means you can swap prices on the fly. (github.com)
Low-latency settlement and tiny minimums: The reference implementation targets ~2s settlement and ~$0.001 minimums—perfect for micro price splits like $0.001 vs $0.003 per call. (github.com)
Enterprise-grade rails: Coinbase’s facilitator includes KYT/OFAC screening and a REST interface to verify and settle payments, making governance and audit easier for decision-makers. (coinbase.com)
Broad ecosystem momentum: Cloudflare added agent-side helpers; facilitators show Base and Solana support; and on-chain usage has surged in recent months, so you’re not experimenting in a vacuum. (developers.cloudflare.com)

The 60-second x402 primer (what you’ll A/B)

Step 1: Client requests your resource.
Step 2: If payment is required, your proxy or server returns HTTP 402 with a JSON “Payment Required Response” that includes one or more acceptable “paymentRequirements.” (github.com)
Step 3: Client pays and retries with an X-PAYMENT header (base64 JSON payload). (github.com)
Step 4: Your proxy verifies/settles the payment locally or via the facilitator (/verify, /settle) and forwards to origin. (docs.cdp.coinbase.com)

Key objects you’ll touch:

Payment Required Response (body of the 402)
paymentRequirements array (you control price, network, asset, payTo, timeout, description, etc.)
X-PAYMENT request header (client-signed payload)
X-PAYMENT-RESPONSE response header (tx hash, network, etc.) (github.com)

Supported v1 kinds today (facilitator example):

exact on base and base-sepolia
exact on solana and solana-devnet (docs.cdp.coinbase.com)

USDC on Base mainnet (ERC-20) address: 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 (6 decimals). (developers.circle.com)

Three “no-new-infra” patterns to A/B test price

Cloudflare edge proxy (Workers + x402 helpers)

Wrap fetch in x402-aware code and inject a payment middleware for specific routes. Randomize price variants at the edge; origin stays untouched. (developers.cloudflare.com)

Managed gateway

Point a hosted x402 gateway at your existing API and get a paid, proxied URL. Use its config to run price splits without touching the origin. (x402gateway.io)

One-line server middleware (gradual rollout)

If you can add middleware, Coinbase’s example shows “paymentMiddleware('0xYourAddress', { '/endpoint': '$0.01' })” for an Express-style server. Start with a low-traffic endpoint and ramp. (github.com)

What to A/B: concrete price hypotheses

Pay-per-request APIs: $0.001 vs $0.003 vs $0.005 per call
AI inference: $0.002 vs $0.004 per prompt (coarse per-request until a metered “upto” scheme lands)
Pay-per-article: $0.01 vs $0.05 with a “first paragraph free” teaser
Blockchain RPC egress: $0.0001 vs $0.00025 per call for speed-tiered routing (as used by x402-powered multi-provider RPC). (x402labs.cloud)

Implementation blueprint: run an A/B test in a week

1) Choose network and asset

Start with USDC on Base: fast, cheap, and supported by facilitator and tooling today. Base USDC has 6 decimals; multiply dollars by 1,000,000 to set maxAmountRequired. Example: $0.01 → 10,000. (docs.cdp.coinbase.com)

2) Emit a 402 with variant-specific paymentRequirements

Return only the assigned variant to prevent client-side cherry-picking. Here’s a minimal 402 for the “exact on Base” scheme with two example prices—pick one per user:

HTTP/1.1 402 Payment Required
Content-Type: application/json
Cache-Control: no-store

{
  "x402Version": 1,
  "accepts": [
    {
      "scheme": "exact",
      "network": "base",
      "resource": "https://api.yourdomain.com/premium/v1/weather",
      "description": "Premium weather endpoint (per request)",
      "mimeType": "application/json",
      "payTo": "0xYourReceivingAddress",
      "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
      "maxAmountRequired": "1000",           // $0.001 (Variant A)
      "maxTimeoutSeconds": 8,
      "extra": { "name": "USD Coin", "version": "2" }
    }
  ]
}

Notes:

maxAmountRequired is in asset atomic units (USDC: 6 decimals). (github.com)
Return exactly one requirement per assignment to avoid mixing variants.
Set Cache-Control: no-store because prices differ by user. (github.com)

3) Assign variants at the edge (sticky, privacy-safe)

Use a stable assignment key so the same user sees the same price:

First request: compute bucket = hash(ip + userAgent + path) % 2
Set a cookie “x402_price_variant=A|B; Max-Age=30d; Secure; SameSite=Lax”
Always honor the cookie on subsequent requests

Cloudflare Worker sketch:

export default {
  async fetch(req: Request, env: Env) {
    const url = new URL(req.url);
    if (url.pathname.startsWith("/premium")) {
      const variant = getOrSetVariant(req);
      if (!hasValidXPayment(req)) {
        const paymentReq = buildPaymentRequired(variant, {
          payTo: env.PAY_TO,
          asset: env.USDC_BASE,
          resource: url.toString(),
        });
        return new Response(JSON.stringify(paymentReq), {
          status: 402,
          headers: {
            "Content-Type": "application/json",
            "Cache-Control": "no-store",
          },
        });
      }
      const verified = await verifyWithFacilitator(req.headers.get("X-PAYMENT"), paymentReq);
      if (!verified) return new Response(JSON.stringify(paymentReq), { status: 402 });
      return fetch(env.ORIGIN + url.pathname + url.search); // forward to origin
    }
    return fetch(env.ORIGIN + url.pathname + url.search);
  }
};

The verify/settle helpers should call Coinbase’s facilitator endpoints (/verify then /settle) and log txHash + networkId from X-PAYMENT-RESPONSE. (docs.cdp.coinbase.com)

4) Verify and settle with the facilitator

GET /v2/x402/supported to discover networks/schemes
POST /v2/x402/verify with the PaymentRequirements and X-PAYMENT header
If valid, execute work and POST /v2/x402/settle; include tx metadata in X-PAYMENT-RESPONSE to the client

This avoids running your own node/wallet and keeps origin code unchanged. (docs.cdp.coinbase.com)

5) Instrumentation: what to log

Store one row per request:

timestamp, assignment_key, variant, price_usd_micros
was_402_shown (bool), paid (bool), facilitator_isValid (bool)
txHash, networkId, latency_ms, http_status
route, geo, userAgent_family

You can compute:

Conversion rate = paid_requests / 402_shown
Revenue per 1k requests
Latency added by verification
Refunds or double-spend anomalies (should be zero if you dedupe by txHash + resource)

Code you can reuse today

Edge: Hono + x402 on Cloudflare Workers

Cloudflare’s docs show payment middleware for Hono and an agent helper to wrap fetch so AI agents automatically pay. This is great for dual-sided tests (some clients pay, some read for free) and for quickly gating a subset of endpoints. (developers.cloudflare.com)

Server: “one-liner” middleware

Coinbase’s examples demonstrate a paymentMiddleware taking your receiving address and a price map. You can A/B by selecting different price maps at runtime (based on cookie or header) without touching handler code. (github.com)

SDKs for agents and Python stacks

Community SDKs exist for FastAPI and LangChain-style agents if you want buyer agents to pay autonomously in tests—useful when experimenting with M2M pricing. (github.com)

Practical examples (end-to-end)

Example 1: Pay-per-inference API

Goal: Find the price point that maximizes revenue/latency trade-off for an LLM endpoint.

Variants: $0.002 vs $0.004 per inference request.
Implementation: Edge proxy returns variant-specific 402; origin untouched.
Measurement: Revenue per 1k calls, p95 latency, drop-off rate after 402.
Tips: Start with 80/20 traffic split and ramp to 50/50 after verifying success/failure modes. Consider “first 3 calls free” via a Worker counter before requiring 402. (developers.cloudflare.com)

Example 2: Premium article paywall (human readers)

Variants: $0.01 vs $0.05 per article.
Implementation: Inject 402 after 2 free paragraphs; paymentRequirements.mimeType matches the article output (e.g., text/html).
Client: Show a minimal UI that pays and retries behind the scenes; store txHash for receipt. (github.com)

Example 3: RPC aggregator monetization

Variants: $0.0001 vs $0.00025 per call.
Implementation: x402 at the RPC gateway; payment unlocks a multi-provider route with failover.
Lesson: Tiny deltas matter at high QPS; run tests for at least a week to smooth weekly cycles. (x402labs.cloud)

Emerging best practices from production pilots

Prefer Base + USDC for early tests. Facilitator support is strong, settlement is fast, and contract address is canonical. Solana support exists—evaluate where your users already are. (docs.cdp.coinbase.com)
Keep amounts in USD terms. Your pricing experiments should be in fiat units (USDC) to avoid token volatility polluting results. (coinbase.com)
One requirement per user, per request. Don’t return multiple paymentRequirements across variants in a single 402; clients could self-select cheaper options. Assign variants server-side. (github.com)
Use maxTimeoutSeconds as a guardrail. Set 5–10s to enforce timely verification and avoid clients hanging; if exceeded, return another 402 with a helpful error string. (github.com)
Log and surface X-PAYMENT-RESPONSE. Persist txHash and networkId for receipts, reconciliation, and support. (github.com)
Handle caching explicitly. 402s can be cached by intermediaries; always set Cache-Control: no-store on 402 responses used for pricing experiments. (github.com)
Compliance-by-default. If you use Coinbase’s facilitator, you inherit KYT/OFAC screening that helps satisfy enterprise risk controls. Pair with your own geo/denylist at the edge. (coinbase.com)
Agents will pay automatically. Cloudflare’s wrapFetchWithPayment and similar client helpers reduce friction—great for M2M experiments and “agent-native” use cases. (developers.cloudflare.com)

Comparing x402 to Lightning’s L402 (so you can pick the right tool)

L402 (Lightning + LSAT) also uses HTTP 402 but authenticates with macaroons + invoice preimages; it’s proven for BTC/Lightning-centric stacks. x402 is chain-agnostic with an HTTP header schema (X-PAYMENT) and facilitator APIs, optimized for stablecoin flows and AI-agent use. If your buyers are Lightning-native, test L402; if they’re in EVM/Solana + USDC, x402 is the faster path to USD-denominated A/B tests. (docs.lightning.engineering)

Risk and governance notes for decision-makers

Replay/double-spend: Record txHash+resource and reject reused proofs. The facilitator’s /verify + /settle flow plus your idempotency checks should make this moot. (docs.cdp.coinbase.com)
Refunds: Not a protocol primitive; implement a customer-care playbook (partial credits via separate onchain transfer, or comped access) and track by txHash.
Fraud and sanctions: Enforce geo rules at the edge; rely on facilitator KYT. Add rate limits per IP/UA to stop scripted probing. (coinbase.com)
Roadmap awareness: Today’s public “scheme” is exact; metered “upto” is discussed in the spec as extensible. Design your internal abstraction so you can swap schemes later without refactoring. (github.com)

Analytics: determine a winner with minimal math

Guardrail metrics: API success rate, p95/p99 latency, refund rate, abandonment after 402.
North-star: Revenue per 1,000 requests and net margin after infra/toll costs.
Test length: Use a sequential test (e.g., always-valid confidence intervals) to stop early when a clear winner emerges; cap at 2–4 weeks to limit drift.
Segmentation: Channel (referrer), geo, bot vs human (heuristic), and “agent” user agents from Cloudflare’s examples. (developers.cloudflare.com)

SQL sketch (BigQuery/Postgres flavor):

SELECT
  variant,
  COUNTIF(was_402_shown) AS challenged,
  COUNTIF(paid) AS paid,
  SAFE_DIVIDE(COUNTIF(paid), COUNTIF(was_402_shown)) AS conversion_rate,
  SUM(price_usd_micros)/1e6 AS revenue_usd,
  1000 * SUM(price_usd_micros)/1e6 / COUNT(*) AS revenue_per_1k
FROM requests
WHERE route = '/premium/v1/weather' AND ts >= CURRENT_DATE - INTERVAL '14 days'
GROUP BY variant;

Putting it all together: a 1-day pilot plan

Hour 1: Choose Base+USDC, set payTo address, confirm facilitator /supported lists “exact/base.” (docs.cdp.coinbase.com)
Hours 2–4: Deploy a Cloudflare Worker proxy that:
- assigns A/B cookie
- returns a variant-specific 402 with maxAmountRequired set to $0.001 (A) or $0.003 (B)
- verifies via /verify and settles via /settle; forwards on success (developers.cloudflare.com)
Hours 5–6: Add request logging for variant, price, paid, txHash, latency.
Hours 7–8: Run smoke tests with an agent client that wraps fetch and auto-pays; confirm X-PAYMENT-RESPONSE returns txHash. (developers.cloudflare.com)
Hours 9–24: Ramp 10% traffic, monitor drop-offs and p95 latency; widen to 50% if error budget holds.

What “no-new-infra” really means

Your origin doesn’t change. All x402 negotiation, verification, and settlement happen at the edge proxy or gateway URL; the origin just receives the paid request like any other. (developers.cloudflare.com)
You can remove x402 instantly. Kill-switch is a DNS or route change; no schema migrations, no key management rollback.

Ecosystem links you’ll actually use

Protocol and headers (X-PAYMENT, X-PAYMENT-RESPONSE), PaymentRequired schema, facilitator API: start here. (github.com)
Supported networks (today): exact on base/base‑sepolia and solana/solana‑devnet. (docs.cdp.coinbase.com)
Cloudflare Workers/Agents snippets (server + agent): fast way to proxy or build agent buyers. (developers.cloudflare.com)
USDC on Base contract (6 decimals) for maxAmountRequired math. (developers.circle.com)
Product overview and compliance posture for stakeholders. (coinbase.com)

Closing: don’t wait for perfect metering to learn your price

You don’t need metered billing or a new account system to test willingness-to-pay. With x402’s exact scheme, a 402 response, and an edge proxy, you can run credible, low-risk pricing experiments this week—on a real user cohort, with real money, and reversible in minutes. Then expand into more sophisticated schemes as the spec evolves.

If you want help shipping an experiment in a day, 7Block Labs can pair with your team to deploy a Worker proxy, wire up facilitator verification, and stand up the analytics you need to decide—before you commit to a full billing build.

References and recent ecosystem notes:

Coinbase x402 spec and examples (headers, schema, facilitator flow). (github.com)
Coinbase x402 product page (KYT/OFAC, positioning). (coinbase.com)
Facilitator API (verify, settle, supported kinds). (docs.cdp.coinbase.com)
Cloudflare Workers/Agents x402 docs (server and agent helpers). (developers.cloudflare.com)
USDC on Base address (for atomic units math). (developers.circle.com)
Adoption momentum (weekly volumes, enterprise partners). (dune.com)

Description: How to A/B test micropayment price points with x402 using an edge proxy, gateway, or one-line middleware—complete with schemas, code sketches, compliance notes, and analytics to ship pricing experiments without touching your origin. (github.com)