Monitor Types Explained
Different services need different types of monitoring. Here’s what each monitor type does and when to use it.
HTTP/HTTPS Monitors
The most common type - checks if a website or API is responding.
How it works:
- Sends a request to your URL
- Checks that it responds with a success code (like 200 OK)
- Measures how long the response took
Best for:
- Websites and web applications
- REST APIs
- Webhooks and endpoints
Example URLs:
https://www.yoursite.comhttps://api.yourservice.com/health
TCP Monitors
Checks if a specific port on a server is open and accepting connections.
How it works:
- Attempts to connect to the server and port
- Confirms the port is listening
- Measures connection time
Best for:
- Database servers
- Mail servers (SMTP, IMAP, POP3)
- Game servers
- Custom applications
Examples:
| Service | Port |
|---|---|
| MySQL | 3306 |
| PostgreSQL | 5432 |
| Redis | 6379 |
| SSH | 22 |
| SMTP | 25 or 587 |
DNS Monitors
Verifies that a domain name resolves correctly to the expected IP address.
How it works:
- Queries DNS servers for your domain
- Checks if it returns the expected record
- Measures resolution time
Best for:
- Critical domains
- Detecting DNS hijacking
- Multi-region DNS setups
What it monitors:
- A/AAAA records (IP addresses)
- CNAME records
- MX records (email)
- TXT records
Keyword Monitors
Checks that a specific word or phrase appears (or doesn’t appear) on a page.
How it works:
- Downloads the page content
- Searches for your keyword
- Passes or fails based on presence/absence
Best for:
- Checking that a page loads correctly (look for “Welcome”)
- Detecting error messages (look for absence of “Error”)
- Verifying content hasn’t been changed
Examples:
| Use Case | Keyword | Should |
|---|---|---|
| Page loads | “Login” | Exist |
| No errors | “Error 500” | Not exist |
| Content check | “Copyright 2025” | Exist |
Choosing the Right Type
| What You’re Monitoring | Recommended Type |
|---|---|
| Website homepage | HTTP/HTTPS |
| API endpoint | HTTP/HTTPS |
| Database server | TCP |
| Email server | TCP |
| Domain DNS | DNS |
| Specific page content | Keyword |
Combining Monitor Types
For critical services, consider using multiple monitor types:
- HTTP monitor - Checks the website is responding
- Keyword monitor - Confirms the right content loads
- TCP monitor - Verifies the database is running
This gives you complete coverage and helps pinpoint issues faster.