# Checkly Uptime Monitoring

**Source**: https://www.checklyhq.com/product/uptime-monitoring/

> Uptime monitoring built for developers. Monitor websites, applications, and infrastructure from 22+ global locations with up to 10-second check intervals — the first layer of detection for issues impacting your end users.

## What it does

- **URL Monitors**: Validate HTTP and HTTPS endpoints for status codes and response times across websites, APIs, and product pages, with SSL certificate expiration alerts.
- **TCP Monitors**: Check database connections, mail servers, and TCP services on specific ports to confirm responsiveness beyond basic host availability.
- **ICMP Monitors**: Ping hosts or IPs at the network layer to measure reachability, latency, and packet loss without requiring open ports.
- **DNS Monitors**: Resolve A, CNAME, MX, and other DNS records with assertion validation to catch propagation and configuration issues early.
- **Heartbeat Monitors**: Track cron jobs, scheduled tasks, and batch processes by expecting pings on schedule and alerting when jobs fail or run late.
- **Monitoring as Code**: Define and deploy monitors via CLI, Terraform, or Pulumi using TypeScript/JavaScript, integrated into CI/CD.
- **High-frequency detection**: Check intervals from 1 second to 24 hours, parallel execution across 22+ locations, and response-time percentile tracking.
- **Alerting logic**: Retry logic, confirmation checks, and failure thresholds to reduce false positives.
- **Global monitoring**: 22+ data centers worldwide to detect regional issues before they become global outages.

## Key facts

- Protocols: **HTTP, HTTPS, TCP, DNS, ICMP**, plus heartbeat monitors.
- Runs from **22+ global locations**; check intervals as fast as every **10 seconds** (1-second available on request).
- Supports monitoring inside private networks via Private Locations.

## Frequently Asked Questions

### What is uptime monitoring?
Uptime monitoring continuously checks whether your websites, APIs, and infrastructure are reachable and responding correctly from outside your network. Checks run on a fixed schedule from multiple global locations, verify each response, and alert your team the moment one fails, so you find out before your users do.

### What types of monitors does Checkly support?
Checkly runs URL/HTTP, TCP, ICMP (ping), DNS, and heartbeat monitors, plus Playwright-based synthetic checks and API checks. You can watch public endpoints, individual ports, DNS records, SSL certificates, and scheduled jobs, all defined in one place as code.

### How fast can Checkly detect an outage?
Checkly runs checks as often as every 10 seconds from 22+ global locations, with 1-second intervals available on request. Multi-location confirmation catches most availability issues within seconds and verifies them across regions before alerting, so detection stays fast without false alarms.

### What does 99.9% or 99.999% uptime mean?
Uptime percentages cap how much downtime is allowed over a period. 99.9% ("three nines") permits about 43 minutes of downtime per month, 99.99% about 4 minutes, and 99.999% ("five nines") about 26 seconds. Uptime monitoring measures your real availability against the SLA you promise.

### How do you prevent false positive alerts?
Checkly confirms failures from multiple locations before alerting, with configurable retries, thresholds, and maintenance windows. Alerts route through Slack, PagerDuty, Opsgenie, and webhooks with escalation logic, so on-call only hears about incidents that are real.

### Can I monitor services behind a firewall?
Yes. Alongside 22+ public locations, Checkly supports private locations, so you can monitor internal APIs, staging environments, and services that are not exposed to the public internet, using the same monitoring-as-code workflow.

### What is the difference between uptime and synthetic monitoring?
Uptime monitoring answers "is it up and responding?" with lightweight, high-frequency checks like HTTP, TCP, ICMP, and DNS. Synthetic monitoring runs full Playwright scripts through real user flows such as login or checkout. Checkly does both, so you can start with uptime and add deeper checks later.

### How does monitoring as code work?
You define monitors in TypeScript or JavaScript with the Checkly CLI, or use the Terraform and Pulumi providers. Version your monitoring configuration, review changes in pull requests, and deploy through your CI/CD pipeline like any other code.

## Related

- [Uptime Monitoring (full page)](https://www.checklyhq.com/product/uptime-monitoring/)
- [Synthetic Monitoring](https://www.checklyhq.com/product/synthetic-monitoring/)
- [API Monitoring](https://www.checklyhq.com/product/api-monitoring/)
- [Heartbeat Monitoring](https://www.checklyhq.com/product/heartbeat-monitoring/)
- [Monitoring as Code](https://www.checklyhq.com/product/monitoring-as-code/)
- [Pricing](https://www.checklyhq.com/pricing/)
- [Start for free](https://app.checklyhq.com/signup/)