RDAP Lookup
Look up structured domain, IP allocation, and ASN registration data.
Explicit network action
Look up public registration data
Enter a domain, IPv4 or IPv6 address, or an AS number. The target type is detected locally before any request.
Request preview
- Detected type
- Waiting for valid input
- Destination
- No request prepared
- Bootstrap
- RDAP.org bootstrap service
- Limits
- 10 seconds · 512 KiB · no retry
This leaves the browser.
RDAP.org receives the lookup target, connection IP, and normal HTTPS metadata, then redirects the browser to the appropriate registry. That registry receives the same target and connection metadata under its own policy. StackCache sends no cookies, credentials, request body, or custom headers.
No request made
Registration details will appear here
Working notes
Use RDAP Lookup with the boundary visible.
RDAP Lookup retrieves structured public registration data for a domain, IP address, or autonomous system number. StackCache detects the target locally, sends one explicit request to the RDAP.org bootstrap service, and displays the bounded authoritative response in memory.
What is RDAP Lookup?
RDAP (Registration Data Access Protocol) is the modern replacement for WHOIS, the 40-year-old protocol used to look up domain, IP address, and ASN registration data. While WHOIS returns unstructured plain text that varies wildly between registries, RDAP returns standardized JSON responses over HTTPS with built-in support for internationalization, access control, and structured data. RDAP uses a bootstrap system: the IANA publishes bootstrap files that map TLDs, IP ranges, and ASN ranges to the authoritative RDAP servers operated by registries (like Verisign for .com, ARIN for North American IPs, RIPE for European IPs). This tool detects whether your input is a domain, IPv4/IPv6 address, or AS number, constructs the correct bootstrap query, and displays the structured response including registration status, registrant entities, nameservers, events (creation, expiration, last update), and notices. The request goes from your browser to RDAP.org (the bootstrap redirector) and then to the authoritative registry.
When to use it
- Domain registration lookup — find the registrar, creation date, expiration date, nameservers, and registration status for any domain.
- IP address ownership — identify which organization has been allocated an IP address or range, useful for investigating network traffic or abuse reports.
- ASN identification — look up the organization and registration details for an autonomous system number seen in BGP routing tables or traceroute output.
- Investigating suspicious domains — check when a domain was registered (recently created domains are a phishing indicator) and which registrar was used.
- Expiration monitoring — verify the expiration date of your own domains to ensure they are renewed before lapsing.
How to use it
- 01Enter a domain, IPv4 or IPv6 address, or an AS number and review the locally detected target type and exact bootstrap URL.
- 02Run the explicit lookup. RDAP.org redirects the browser to the registry responsible for that resource.
- 03Review registration status, identifiers, ranges, events, entities, nameservers, notices, or the raw bounded JSON response.
Common mistakes
- Expecting full contact data — many registries redact registrant contact information under GDPR and privacy policies. RDAP returns only what the registry chooses to publish.
- Confusing RDAP with DNS — RDAP returns registration data (who registered a domain), not DNS resolution data (where a domain points). Use a DNS lookup tool for records.
- Rate limiting — registries rate-limit RDAP queries. If you get errors, wait before retrying. Bulk lookups should be spaced out.
- IP vs domain confusion — entering an IP address returns the IP allocation record from a Regional Internet Registry, not the domain hosted on that IP. These are different registries with different data.
Synthetic example
Autonomous system lookup
Input
AS13335
Result
Structured registration data returned by the authoritative Regional Internet Registry RDAP service
RDAP vs WHOIS
| Feature | Feature | RDAP | WHOIS |
|---|---|---|---|
| Protocol | HTTPS + JSON | TCP port 43, plain text | |
| Response format | Standardized JSON | Free-form text (varies by registry) | |
| Internationalization | Built-in Unicode support | Limited, ASCII-centric | |
| Access control | Structured, per-field redaction | All or nothing | |
| Bootstrap/discovery | IANA bootstrap files | Hardcoded server lists |
Related standards
Limits and data boundary
- The target and normal connection metadata are disclosed to RDAP.org and the authoritative registry after you submit.
- Authoritative servers can redact data, rate-limit requests, return different extension fields, or block browser access through CORS.
- The result is a current provider response, not proof of ownership, routing, DNS health, reputation, availability, or legal status. Results remain in memory only.
Frequently asked questions
- What is RDAP?
- RDAP (Registration Data Access Protocol) is the modern, structured replacement for WHOIS. It returns JSON registration data for domains, IP addresses, and autonomous system numbers from authoritative registries.
- How is RDAP different from WHOIS?
- RDAP returns structured JSON instead of free-form text, supports internationalization and access control, and uses HTTPS. WHOIS is a legacy protocol with inconsistent formatting across registries.
- Can I look up any domain?
- You can look up domains, IPv4/IPv6 addresses, and AS numbers. Results depend on the authoritative registry — some redact contact data under privacy policies like GDPR.
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