Checks

A check is one thing ZeroDrop watches, probed from every active location on a fixed interval. There are two types: HTTP/HTTPS and SMTP. This page covers every field; for how results become an up/down verdict, see Consensus & status.

Common options

These apply to both check types.

Option	Default	Notes
Name	required	A label for the check. Must be unique within your account.
Enabled	on	Turn a check off to stop probing without deleting it.
Interval	60 s	How often each location probes. 60 seconds is the minimum.
Timeout	5 s	A probe that takes longer than this is recorded as a failure.
Locations	all	Every check runs from all active locations. There's no per-check picker.
Public badges	off	Publish status, uptime and SSL badges for this check. See Dashboards.

Your account has a maximum number of checks and a minimum interval. Both are shown on the Settings page and can be raised on request.

HTTP / HTTPS checks

An HTTP check requests a URL and decides success from the response.

Option	Default	Notes
URL	required	The full `http(s)://` URL to request.
Method	`GET`	Any standard HTTP method.
Expected status	`200`	The probe fails if the final response status differs.
Body pattern	none	Optional substring that must appear in the response body.
Follow redirects	on	When off, a `3xx` is the final response (useful to assert a redirect).
Max redirects	5	How many hops to follow before giving up.

TLS certificate options (HTTPS)

For https:// URLs you can also control how the certificate is treated:

Option	Default	Notes
SSL certificate must validate	on	The server's certificate must chain to a trusted root and match the host. Turn this off to monitor a host with a self-signed or otherwise untrusted certificate.
Fail when fewer days left than	7 days	The check fails once the certificate has fewer than this many days of validity remaining, so you're alerted before it expires rather than after. Set it to Off to ignore expiry.

On every probe ZeroDrop also records, for free:

DNS time, time to first byte (TTFB) and total latency.
The response size in bytes.
For HTTPS, the TLS certificate chain: issuer, subject and days until expiry, so you can spot a certificate that's about to lapse.

Examples

Health endpoint: GET https://api.example.com/healthz, expected status 200, body pattern ok.
Assert a redirect: GET http://example.com, follow redirects off, expected status 301.
Authenticated API liveness: GET https://api.example.com/v1/models, expected status 401. A 401 proves the API is up and enforcing auth.

SMTP checks

An SMTP check connects to a mail server, reads its welcome banner, and times how long that took.

Option	Default	Notes
Host	required	The mail server hostname.
Port	25	Common choices: `25` (inbound MX), `587` (submission).
STARTTLS	on	When on, ZeroDrop issues `EHLO` + `STARTTLS` and inspects the TLS certificate.
Expected banner	none	Optional substring that must appear in the `220` greeting.

The same TLS certificate options as HTTPS checks apply to the certificate presented during STARTTLS:

Option	Default	Notes
SSL certificate must validate	on	The STARTTLS certificate must chain to a trusted root and match the host. Turn off for self-signed mail servers.
Fail when fewer days left than	7 days	Alerts before the mail server's certificate expires. Set to Off to ignore expiry.

The probe succeeds when the server answers with a 220 greeting (and, if configured, the banner pattern matches and STARTTLS negotiates cleanly with a certificate that passes the checks above). The headline metric for SMTP checks is the welcome time: how quickly the banner arrived.

Editing and deleting

You can change any option on an existing check at any time; the new configuration takes effect on the next interval. Deleting a check removes it from every location and stops all of its alerts. The console asks you to confirm first.