---
title: "Website monitoring glossary — every term explained"
description: "Plain-English definitions for 47 website monitoring, uptime, performance, SEO and security terms."
canonical: "https://lemwatch.com/glossary"
source: "https://lemwatch.com"
---

# Website monitoring glossary

> 47 monitoring terms defined without jargon — what each one measures, why it matters, and how it shows up in a real monitoring dashboard.

## All terms

- Uptime
- Downtime
- Five Nines
- SLA
- MTTR
- Incident
- Alert Fatigue
- Core Web Vitals
- LCP
- CLS
- INP
- TTFB
- Lighthouse
- Page Speed
- CDN
- SEO
- Sitemap
- robots.txt
- Canonical Tag
- Indexing
- IndexNow
- Schema Markup
- SSL/TLS
- CSP
- HSTS
- Security Headers
- DMARC
- SPF
- DKIM
- DNS
- Domain Expiry
- RDAP
- Broken Link
- Visual Regression
- Change Detection
- Money Page
- Website Monitoring
- Synthetic Monitoring
- False Positive
- Recovery Time Objective
- Recovery Point Objective
- Mean Time Between Failures
- Service Level Objective
- Service Level Indicator
- Error Budget
- Real User Monitoring
- Status Page

## All 47 pages in this section

- [Alert Fatigue](https://lemwatch.com/glossary/alert-fatigue)
- [Broken Link](https://lemwatch.com/glossary/broken-link)
- [Canonical Tag](https://lemwatch.com/glossary/canonical)
- [CDN (Content Delivery Network)](https://lemwatch.com/glossary/cdn)
- [Change Detection](https://lemwatch.com/glossary/change-detection)
- [CLS (Cumulative Layout Shift)](https://lemwatch.com/glossary/cls)
- [Core Web Vitals (CWV)](https://lemwatch.com/glossary/core-web-vitals)
- [CSP (Content Security Policy)](https://lemwatch.com/glossary/csp)
- [DKIM (DomainKeys Identified Mail)](https://lemwatch.com/glossary/dkim)
- [DMARC (Domain-based Message Authentication, Reporting and Conformance)](https://lemwatch.com/glossary/dmarc)
- [DNS (Domain Name System)](https://lemwatch.com/glossary/dns)
- [Domain Expiry](https://lemwatch.com/glossary/domain-expiry)
- [Downtime](https://lemwatch.com/glossary/downtime)
- [Error Budget](https://lemwatch.com/glossary/error-budget)
- [False Positive](https://lemwatch.com/glossary/false-positive)
- [Five Nines (99.999% uptime)](https://lemwatch.com/glossary/five-nines)
- [HSTS (HTTP Strict Transport Security)](https://lemwatch.com/glossary/hsts)
- [Incident](https://lemwatch.com/glossary/incident)
- [Indexing](https://lemwatch.com/glossary/indexing)
- [IndexNow](https://lemwatch.com/glossary/indexnow)
- [INP (Interaction to Next Paint)](https://lemwatch.com/glossary/inp)
- [LCP (Largest Contentful Paint)](https://lemwatch.com/glossary/lcp)
- [Lighthouse](https://lemwatch.com/glossary/lighthouse)
- [Money Page](https://lemwatch.com/glossary/money-page)
- [Website Monitoring](https://lemwatch.com/glossary/monitoring)
- [Mean Time Between Failures (MTBF)](https://lemwatch.com/glossary/mtbf)
- [MTTR (Mean Time To Recovery)](https://lemwatch.com/glossary/mttr)
- [Page Speed](https://lemwatch.com/glossary/page-speed)
- [RDAP (Registration Data Access Protocol)](https://lemwatch.com/glossary/rdap)
- [robots.txt](https://lemwatch.com/glossary/robots-txt)
- [Recovery Point Objective (RPO)](https://lemwatch.com/glossary/rpo)
- [Recovery Time Objective (RTO)](https://lemwatch.com/glossary/rto)
- [Real User Monitoring (RUM)](https://lemwatch.com/glossary/rum)
- [Schema Markup](https://lemwatch.com/glossary/schema-markup)
- [Security Headers](https://lemwatch.com/glossary/security-headers)
- [SEO (Search Engine Optimization)](https://lemwatch.com/glossary/seo)
- [Sitemap](https://lemwatch.com/glossary/sitemap)
- [SLA (Service Level Agreement)](https://lemwatch.com/glossary/sla)
- [Service Level Indicator (SLI)](https://lemwatch.com/glossary/sli)
- [Service Level Objective (SLO)](https://lemwatch.com/glossary/slo)
- [SPF (Sender Policy Framework)](https://lemwatch.com/glossary/spf)
- [SSL/TLS (Secure Sockets Layer / Transport Layer Security)](https://lemwatch.com/glossary/ssl)
- [Status Page](https://lemwatch.com/glossary/status-page)
- [Synthetic Monitoring](https://lemwatch.com/glossary/synthetic-monitoring)
- [TTFB (Time To First Byte)](https://lemwatch.com/glossary/ttfb)
- [Uptime](https://lemwatch.com/glossary/uptime)
- [Visual Regression](https://lemwatch.com/glossary/visual-regression)


## Related

- [Help centre](https://lemwatch.com/help)
- [Lemwatch pricing](https://lemwatch.com/pricing)
- [All monitoring checks](https://lemwatch.com/features)