x402.cron2systemd 402 payments

x402.cron2systemd.dev

x402 payment inspector and related checks

Seventy client-side tools for payment-required headers, payTo, network, USDC amounts, EIP-3009 previews, facilitator responses, and client checklists. The flagship parses a pasted 402 and can try a CORS fetch. Nothing on this site sends a payment.

Flagship

x402 payment inspector

Parse an HTTP 402 or x402 challenge for network, payTo, asset, and amount. Fetch is best-effort because of CORS.

 Parse

payment-required header

Decode a payment-required header from raw JSON or base64 JSON.

 Parse

payTo address extract

List every payTo value and checksum 20-byte hex addresses.

 Parse

x402 network check

Check a requirement network against a local list of chain ids and known USDC addresses.

 Price

Atomic USDC amount

Turn an atomic token amount into a human amount. USDC uses 6 decimals.

 Parse

Accept challenge parse

List payment requirements from an accepts array or payment headers.

 Price

Resource price table

Table resource, network, and amount from one or more requirements.

 Price

Base USDC payTo verify

Check that payTo is an address and the asset matches known USDC for that network.

 Parse

Facilitator hint

Show extra facilitator-like fields from a challenge. Does not call a facilitator.

 Parse

maxTimeoutSeconds check

Flag a payment timeout under 5 seconds or over an hour.

 Parse

MIME type match

Compare the requirement mimeType with the type you expect to receive after paying.

 Parse

x402 versus plain 402

Tell an x402 challenge apart from a plain HTTP 402 that has no payment fields.

 Probe

Paywall endpoint probe

GET a URL and report whether the browser can see an HTTP 402 challenge.

 Probe

Paid 200 versus 402

Compare an unpaid challenge paste with a paid response paste.

 Parse

exact scheme / EIP-3009

Check for scheme exact and the extra name/version used with EIP-3009 USDC.

 Parse

Paywall header pretty print

Pretty-print response headers from a pasted HTTP message.

 Price

Compare resource prices

Compare amounts across several pasted challenges, separated by blank lines.

 Probe

llms.txt payment finder

Highlight llms.txt lines that mention 402, x402, or payment. Fetch when CORS allows.

 Price

Settlement network mismatch

Flag a requirement whose network is not the network you expect to settle on.

 Checklist

x402 client checklist

A local checklist for building a client that can read a 402 and retry after paying.

 Headers

WWW-Authenticate payment

Parse a WWW-Authenticate header on a 402, including a Payment scheme and its parameters.

 Headers

payment-response header

Decode a payment-response header from JSON or base64 JSON.

 Headers

X-PAYMENT header

Decode an X-PAYMENT or payment-signature header. The signature is redacted in the result.

 Headers

x402Version check

Read x402Version values and flag anything other than 1 or 2.

 Headers

Payment header inventory

List response headers whose names look like payment or authenticate fields.

 Headers

Encode payment-required

Encode payment JSON as a standard and URL-safe base64 payment-required value.

 Headers

Decode payment base64

Decode a base64 or base64url payment JSON value.

 Headers

Challenge header style

Tell a body accepts challenge, a payment-required header, and WWW-Authenticate apart.

 Headers

CORS expose-headers check

Check whether a pasted 402 exposes payment headers to the browser.

 Headers

Challenge error extract

Pull error and invalidReason strings out of a challenge or facilitator JSON.

 Build

Payment requirement builder

Build one payment requirement object. Nothing is signed or sent.

 Build

Accepts array builder

Build an accepts array with two optional requirements.

 Build

HTTP 402 message builder

Build an HTTP 402 message with a JSON body and a payment-required header.

 Build

Requirement field validator

Check a requirement for the fields a client needs before it can pay.

 Build

x402 v1 shape check

Check a paste against the version 1 accepts shape.

 Build

x402 v2 shape check

Check a paste for a version 2 payment-required shape.

 Build

Duplicate accepts detector

Flag repeated scheme, network, asset, and payTo options.

 Build

Scheme allowlist

Allow only the local scheme names exact and upto.

 Build

Resource URL match

Compare requirement resource URLs with the URL you meant to call.

 Build

outputSchema peek

Show an outputSchema object when the challenge includes one.

 Amount

Human USDC to atomic

Convert a human token amount to an atomic integer. USDC uses 6 decimals.

 Amount

Atomic amount batch

Convert one atomic amount per line into a human amount.

 Amount

Amount alias agreement

Check that amount and maxAmountRequired agree when both are present.

 Amount

Amount scale guess

Heuristic: flag an amount that looks like human units rather than 6-decimal atomic units.

 Amount

Zero amount flag

Fail a requirement whose amount is zero.

 Amount

Price for N calls

Multiply an atomic price by a call count and show the total.

 Amount

Atomic amount delta

Compare two atomic amounts and show the difference.

 Amount

Atomic fee buffer

Add a percent buffer to an atomic amount for a local budget. This does not change a challenge.

 Amount

Decimals from asset

Look up decimals for asset addresses on the local USDC list.

 Amount

USDC price ladder

Show common USDC prices in atomic units, plus an optional custom amount.

 EIP-3009

EIP-3009 typed data preview

Preview the EIP-712 typed data for TransferWithAuthorization. No wallet is opened.

 EIP-3009

EIP-3009 digest preview

Compute the EIP-712 domain separator, struct hash, and digest locally. This is not a signature.

 EIP-3009

EIP-3009 nonce check

Check that a nonce is 32 bytes of hex.

 EIP-3009

EIP-3009 validity window

Compare validAfter and validBefore with the current time.

 EIP-3009

EIP-3009 domain name

Compare extra.name and extra.version with the usual USD Coin / 2 domain.

 EIP-3009

EIP-3009 value vs amount

Compare an authorization value with the requirement amount.

 EIP-3009

Recipient versus payTo

Compare an authorization recipient with payTo.

 EIP-3009

EIP-3009 authorization checklist

A local checklist before you sign an EIP-3009 authorization.

 Network

Chain id lookup

Resolve a network name, chain id, or CAIP-2 id on the local list.

 Network

USDC address reverse lookup

Find which local network a USDC address belongs to.

 Network

EIP-55 checksum

Checksum a 20-byte hex address and report mixed-case mismatches.

 Network

payTo address kind

Classify a payTo string as an EVM address, a Solana address, or something else.

 Network

CAIP-2 network parse

Split an eip155 or solana CAIP-2 network id and match it locally.

 Network

Network alias normalize

Map aliases such as 8453, eip155:8453, and base to one name.

 Network

Multiple networks in accepts

Warn when one challenge lists more than one settlement network.

 Facilitator

Facilitator verify decoder

Read a facilitator verify JSON payload. The page does not call a facilitator.

 Facilitator

Facilitator settle decoder

Read a facilitator settle JSON payload, including a transaction id when present.

 Facilitator

Payment payload decoder

Show the shape of a client payment payload and redact the signature.

 Facilitator

Settlement transaction extract

Pull EVM transaction hashes and long Solana signatures out of a paste.

 Facilitator

invalidReason glossary

Look up a facilitator invalidReason string on a local glossary.