IP in CIDR check API
Checks one IPv4 or IPv6 address against up to 100 CIDR blocks and returns, for each, whether it contains the address, plus the list of blocks that do. Blocks of the other IP version never match.
POST https://api.lookproof.dev/v1/ip/contains
Updated 2026-10-09
Examples use the Base (eip155:8453) network.
Input
A JSON body with content-type: application/json.
| Name | Type | Required | Limits | Description |
|---|---|---|---|---|
ip | string | Yes | 2–64 characters | An IPv4 or IPv6 address, without a zone (%). |
cidrs | array of string | Yes | 1–100 items; each 2–64 characters | 1 to 100 networks in CIDR form; blocks of the other IP version never match. |
Example request
curl -i -X POST https://api.lookproof.dev/v1/ip/contains \
-H 'content-type: application/json' \
-d '{"cidrs": ["192.0.2.0/24", "198.51.100.0/24", "2001:db8::/32"], "ip": "192.0.2.10"}'import asyncio
import os
from eth_account import Account
from x402 import x402Client
from x402.http.clients import x402HttpxClient
from x402.mechanisms.evm import EthAccountSigner
from x402.mechanisms.evm.exact import register_exact_evm_client
async def main() -> None:
signer = EthAccountSigner(Account.from_key(os.environ["EVM_PRIVATE_KEY"]))
client = register_exact_evm_client(x402Client(), signer, networks="eip155:8453")
async with x402HttpxClient(client) as http:
response = await http.post('https://api.lookproof.dev/v1/ip/contains', json={'cidrs': ['192.0.2.0/24', '198.51.100.0/24', '2001:db8::/32'], 'ip': '192.0.2.10'})
response.raise_for_status()
print(response.json())
asyncio.run(main())
import { wrapFetchWithPaymentFromConfig } from "@x402/fetch";
import { ExactEvmScheme } from "@x402/evm";
import { privateKeyToAccount } from "viem/accounts";
const account = privateKeyToAccount(process.env.EVM_PRIVATE_KEY);
const fetchWithPayment = wrapFetchWithPaymentFromConfig(fetch, {
schemes: [{ network: "eip155:8453", client: new ExactEvmScheme(account) }],
});
const response = await fetchWithPayment("https://api.lookproof.dev/v1/ip/contains", {
method: "POST",
headers: { "content-type": "application/json" },
body: JSON.stringify({"cidrs": ["192.0.2.0/24", "198.51.100.0/24", "2001:db8::/32"], "ip": "192.0.2.10"}),
});
console.log(await response.json());
curl: unpaid request — returns 402 with the price (PAYMENT-REQUIRED). The Python and JavaScript clients pay it and send the request again. Only ordinary wallets (EOA) can pay; smart-contract wallets get a 402 without charge. See payments.
Example response
{
"checked_at": "2026-10-24T12:00:00Z",
"data": {
"contained": true,
"ip": "192.0.2.10",
"matches": [
"192.0.2.0/24"
],
"results": [
{
"cidr": "192.0.2.0/24",
"contains": true
},
{
"cidr": "198.51.100.0/24",
"contains": false
},
{
"cidr": "2001:db8::/32",
"contains": false
}
]
},
"endpoint": "ip.contains",
"findings": [],
"meta": {
"cache_hit": false,
"duration_ms": 42,
"fresh_until": "2026-10-24T12:05:00Z",
"observed_at": "2026-10-24T12:00:00Z",
"resolver": null,
"source": "offline"
},
"request_id": "req_aaaaaaaaaaaaaaaaaaaaaaaaaa",
"schema_version": "1.0",
"status": "ok"
}Response fields
| Field | Meaning |
|---|---|
request_id | Unique id of this request. Quote it when you contact support. |
endpoint | The endpoint id, for example mail.spf. |
schema_version | Version of the response format, currently 1.0. |
checked_at | When the check ran (ISO 8601, UTC). |
status | ok, info, warning or error from the worst finding, or unknown when the check was incomplete. unknown is not an error in the domain. |
data | The check's own data. Its fields are listed below. |
findings | What was found: code, severity, message, explanation and evidence. |
meta | Duration, cache use, resolver and how long the result stays fresh. |
Fields in data
| Field | Type |
|---|---|
ip | string |
contained | boolean |
matches | array of string |
results | array of CidrMatch |
Status codes
| Status | Code | Meaning | Do you pay? |
|---|---|---|---|
| 200 | — | The result is delivered, also when it has negative findings. | Yes: charged once per payment; redelivery of the same payment is free |
| 402 | — | Payment is required, or the attached payment was refused. The body states the price. | No |
| 400 | bad_request | The request is malformed. | No |
| 409 | payment_in_progress, payment_bound_to_other_request | This payment is already being processed, or it is bound to a different request. No new payment is taken. | No |
| 413 | payload_too_large | The body is larger than 64 KB. | No |
| 422 | invalid_input | The input failed validation on a request that carries a payment; nothing is charged. Without a payment, invalid input gets a 402 whose error field names the problem. | No |
| 429 | rate_limited | Too many requests from this IP address or payer. | No |
| 502 | check_failed | The check could not be completed. | No |
| 503 | busy, unavailable, payments_unavailable | The service is busy or temporarily unavailable. | No |
| 504 | deadline_exceeded | The check ran out of time. | No |
Errors use the common error body. See errors.