Uptime monitors check your websites, APIs and network services from the outside, the way your users reach them. No agent is needed.
Monitor types
| Type | Checks |
|---|---|
| HTTP(S) | A URL answers with an expected status code, optionally containing a keyword. Uses GET or HEAD. |
| TCP port | A host accepts connections on a port, such as a database or mail server. |
| Ping | A host answers ICMP ping. |
| DNS | A record (A, AAAA, CNAME, MX, NS or TXT) resolves. With an expected value, it passes if any record contains it. |
A monitor that's down raises a critical Monitor down alert to every enabled channel.
Check interval and timeout
Choose how often to check, from every minute to every hour, and how long to wait for an answer (5 to 30 seconds). A failed check is retried once a couple of seconds later before the monitor is marked down. That avoids alerts for one dropped packet.
HTTP options
- Expected status codes: one or more codes and ranges, like
200-299, 301. Anything else counts as down. - Keyword: the page must contain this text (upper and lower case don't matter). That's handy for catching error pages that still return 200. It isn't checked for HEAD requests.
- Redirects are followed (up to 5).
- Requests identify themselves as
Alertly-Monitor/1.0, so you can allow them through firewalls or exclude them from analytics.
SSL certificate and domain expiry
For HTTPS monitors, Alertly.Net checks the certificate every 6 hours. The check is on by default. Under Expiry warnings you choose how many days ahead to be warned (1 to 90, 14 by default). The alert turns critical in the last 7 days, and you're warned right away if the certificate is invalid.
Turn on domain expiry to be reminded before the domain registration lapses: 30 days ahead by default (1 to 180), critical in the last 7 days. The registration date is looked up through public RDAP once a day.
Response times and uptime
Each monitor page shows uptime for the last 24 hours, 7 and 30 days, response times, daily uptime for the last 90 days, certificate and domain details, and recent failures with the error message. You can add monitors to a status page.
Pausing
Use Pause to stop checking, for example while a site is being rebuilt. Open alerts close quietly, and nothing is sent until you choose Resume.
Private addresses
For security, monitors can only reach public internet addresses. Addresses like 10.x, 192.168.x or localhost are refused. To watch internal services, install the agent on a server inside that network and monitor the service or container instead.