Call before signing a Bitcoin transaction when you need chain context for its in
Call before signing a Bitcoin transaction when you need chain context for its inputs: whether each prevout exists, whether it is already spent, its value in sats and its confirmations. Resolves up to 10 inputs against a public explorer at about one request per second, so a full batch can take over 20 seconds; figures reflect chain state at checked_at. Describes on-chain facts with source links; never advises whether to sign.
Answeringour last check, 2026-09-28
1 of 1checks answered this week
39 msmedian answer time
$0.1listed price per call
$0.1price it asked us
Paid test badge: not yet. The checks above are free: we call the tool without paying and read the payment request it sends back. The Verified badge needs paid calls whose answers match the promised output, and nobody can buy a badge.
Endpoint
POST https://preflight402.com/v1/btc/tx-context
| Category | Market data |
|---|---|
| Provider host | preflight402.com |
| Networks | eip155:8453 |
| Payment schemes | exact |
| Self-reported calls, 30 days | 1 from 1 payers (the provider's figure, not ours) |
Our checks, last 30 days
| Day | Result | HTTP | Asked | Time |
|---|---|---|---|---|
| 2026-09-28 | valid payment request | 402 | $0.1 | 39 ms |
Example input (from the provider)
{
"body": {
"inputs": [
{
"txid": "4a5e1e4baab89f3a32518a88c31bc87f618f76673e2cc77ab2127b7afdeda33b",
"vout": 0
}
]
},
"bodyType": "json",
"method": "POST",
"type": "http"
}
Promised output schema (from the provider)
{
"$schema": "https://json-schema.org/draft/2020-12/schema",
"properties": {
"input": {
"additionalProperties": false,
"properties": {
"body": {
"additionalProperties": false,
"properties": {
"inputs": {
"items": {
"additionalProperties": false,
"properties": {
"txid": {
"pattern": "^[0-9a-f]{64}$",
"type": "string"
},
"vout": {
"maximum": 100000,
"minimum": 0,
"type": "integer"
}
},
"required": [
"txid",
"vout"
],
"type": "object"
},
"maxItems": 10,
"minItems": 1,
"type": "array"
},
"network": {
"default": "mainnet",
"enum": [
"mainnet",
"testnet"
],
"type": "string"
}
},
"required": [
"inputs"
],
"type": "object"
},
"bodyType": {
"enum": [
"json",
"form-data",
"text"
],
"type": "string"
},
"method": {
"enum": [
"POST"
],
"type": "string"
},
"type": {
"const": "http",
"type": "string"
}
},
"required": [
"type",
"method",
"bodyType",
"body"
],
"type": "object"
},
"output": {
"properties": {
"example": {
"type": "object"
},
"type": {
"type": "string"
}
},
"required": [
"type"
],
"type": "object"
}
},
"required": [
"input"
],
"type": "object"
}