How we find the expiration date
Every domain registry publishes registration data, and for years the way to read it was WHOIS: free-form text that each registry formatted however it liked. Its successor is RDAP, which returns the same information as structured JSON. ICANN made RDAP the official source for generic top-level domains in January 2025.
When you enter a domain, we look up which RDAP server is responsible for its TLD in the IANA registry, ask that server about the domain and read the expiration date from the answer. You get the date, and the full RDAP response is in the details: registrar, registration date, status flags such as clientTransferProhibited, and the name servers.
Enter the registered domain, not a subdomain
Registries only know about the domain that was actually bought. For blog.example.com or www.example.com, check example.com. A subdomain usually comes back as "most likely does not exist", because to the registry it doesn't.
When there's no answer
Not every country-code TLD runs an RDAP server yet, and some that do leave out the expiration date for privacy or policy reasons. In that case the check says no RDAP data was found for the TLD. The registrar's control panel remains the reliable source for those domains.
What happens when a domain expires
Less than people fear, at first, and more than they expect later on. Most registrars keep an expired domain parked for a grace period, often up to 30–45 days, during which you can still renew at the normal price, though the website and email typically stop working right away. After that comes a redemption period, usually 30 days, when getting the domain back costs a hefty fee. Then it's released, and domains with any traffic or backlinks tend to get snapped up by drop-catching services within minutes.
Renewal emails go to whatever address was on the account when the domain was registered. Years later that's often a former employee's inbox, which is how well-run companies lose domains.
Get a reminder that actually reaches you
A Domain monitor checks the expiration date daily and notifies you 30, 10 and 1 day before it, through the channels you actually read: email, SMS, a phone call, Telegram, Slack, Pushover or a webhook.