Look up availability and RDAP data for any domain. Add it to your watchlist and get an email when it becomes available, nears expiry, or anything changes.
Waiting for a domain to drop
You want a name that's taken. We check it daily and email you the day it becomes available.
Protecting your brand
You own a domain and want to know when lookalikes get registered or released. We track them and alert you.
Managing your own domains
Multiple domains with different expiry dates. We send reminders before anything lapses.
Integrating domain data into your app
One GET request returns structured RDAP data. Free for basic use, no account required. Add an API key for more.
You spotted myproject.com two years ago. It's taken. The site has shown a blank page for months. Some owners forget to renew, others abandon their projects. The domain eventually expires and becomes available again, sometimes for a few hours, sometimes a few days. If you weren't watching, someone else grabbed it.
Domain Sentinel checks the domain daily and emails you the moment it becomes available.
Learn more →Your store has run on acme.fr for three years. A competitor registers acme.net and siphons traffic meant for you. Or a squatter grabs acme.io to sell it back at a markup. These things happen without warning.
Add acme.de, acme.io, acme.co to your watchlist. You get an alert the moment any of them changes status.
Learn more →You have a dozen domains. The email on one of them is an old work inbox you no longer check. The registrar reminder bounces. The card on file has expired. The domain goes to auction without you noticing.
Domain Sentinel alerts you 60 days before expiry, then 30, 7 and 1. You won't miss a renewal even if your registrar stops reaching you.
Learn more →You're building a tool that lets users bring their own custom domain. At every input, your app needs to check availability. Or you're running a brand-name generator that filters results in real time based on what's free.
GET /v1/lookup/:domain returns RDAP data as JSON. Free for basic use, no account needed. For higher volumes, an API key is enough.
Learn more →One endpoint, no setup. Pass a domain name, get back structured RDAP data. Anonymous requests are free up to 5 per minute. Create a free API key for unlimited access.
Full API reference# Anonymous — 5 req/min, no account needed
curl https://api.domain-sentinel.com/v1/lookup/github.com
# With API key — unlimited (free)
curl -H "Authorization: Bearer ds_your_key" \
https://api.domain-sentinel.com/v1/lookup/github.com
# Response
{
"domain": "github.com",
"available": false,
"entities": [{ "role": "registrar", "name": "MarkMonitor Inc." }],
"statuses": ["clientTransferProhibited"],
"events": [
{ "eventAction": "registration", "eventDate": "2007-10-09T..." },
{ "eventAction": "expiration", "eventDate": "2026-10-09T..." }
]
}Start for free. Paid plans with higher limits are in the works.
Everything you need to monitor domains and use the API.
Higher limits, priority support, and advanced monitoring features.
Domain Sentinel is a domain verification and monitoring tool built on the RDAP protocol, the structured successor to WHOIS. For every domain queried, the platform retrieves the data published by the registrar: availability, EPP statuses, nameservers, registration and expiration dates, DNSSEC configuration.
Checking takes a few seconds, no sign-up needed. If the domain is available, you can register it with your usual registrar. If it's taken, you set an alert and get an email the day it expires or becomes available again.
Monitoring also covers the domains you already own. Nameserver changes, unexpected transfers, an approaching expiration date: each change triggers a notification. No need to check manually.
For developers, the public API exposes a REST endpoint that returns a structured JSON response, compatible with any language. Query domain availability or detect a status change without WHOIS scraping. Domain Sentinel covers TLDs listed in the IANA bootstrap, updated daily.