IP-to-ASN Lookup API (fast hehe)

This API allows you to lookup the ASN, country, country name, and provider name for a given IPv4 or IPv6 address. This API uses an very Optimized Cache to have very fast response times. The API does Support Quic (http3) and http2 to deliver fast responses! ⚡

Auto-detection feature: If no IP parameter is provided, the API automatically uses the client's IP address from the request.

Base URL

https://cdn.t-w.dev/whois?ip={IP}&locale={locale}

• ip (optional) – IPv4 or IPv6 address to query. If omitted, uses client IP
• locale (optional) – de, en, or both (default: both)

---

Request

Method

• GET or POST

Parameters

Name	Type	Required	Description
ip	string	No	IPv4 or IPv6 address to query. If omitted, automatically uses the client's IP address
locale	string	No	Language for country_name: de, en, both

---

Response

Success (200)

Field	Type	Description
ip	string	The queried IP address (provided or auto-detected)
asn	string	Autonomous System Number
country	string	2-letter country code of the ASN
country_name	string	Localized country name (locale applied)
description	string	Cleaned provider name (normalized)
logo	string	Provider logo (not all)

Example with specified IP:

{
  "ip": "8.8.8.8",
  "asn": "15169",
  "country": "US",
  "country_name": "United States / Vereinigte Staaten",
  "description": "Google",
  "logo": "https://cdn.t-w.dev/img/Google.webp"
}

Example using client IP (no ip parameter):

curl https://cdn.t-w.dev/whois

{
  "ip": "203.0.113.45",
  "asn": "64512",
  "country": "DE", 
  "country_name": "Germany / Deutschland",
  "description": "Example ISP",
  "logo": null
}

Error (400+)

Field	Type	Description
error	string	Description of the problem

Possible errors:

{ "error": "Invalid IP address" }

{ "error": "ASN not found for given IP" }

---

API Flow

flowchart TD
    A[Client Request] --> B{IP parameter provided?}
    B -- No --> F2[Use Client IP from Request]
    B -- Yes --> D{IP valid?}
    D -- No --> E[Return Error: Invalid IP address]
    D -- Yes --> F[Lookup IP in ASN database]
    F2 --> F
    F --> G{ASN found?}
    G -- Yes --> H[Return JSON with ip, asn, country, country_name, description, logo]
    G -- No --> I[Return Error: ASN not found]