Summary: The APM sub-discipline called RUM detects issues in the browser experience, whereas observability identifies sources of those issues, as well as security risks.
With cloud systems and online services now dominating business operations, browsers have become the unsung heroes that drive employee productivity. Ironically, they’re also one of the most overlooked weak spots in many companies’ IT stacks.
When used without adequate oversight, browsers can expose organizations to significant security risks. Fortunately, solutions like observability and APM bring the insights needed to mitigate these threats. Let’s break down what these terms mean and how each can benefit your organization.
Short for Application Performance Monitoring, APM is a set of tools and practices that help organizations track how their software applications perform. Plainly speaking, it shows whether apps are responsive, reliable, and functioning as expected. By providing detailed insights into specific app components, APM enables IT teams to quickly identify bottlenecks and resolve them before users are affected.
First and foremost, Application Performance Monitoring is crucial for keeping software applications running smoothly. It enables teams to detect and fix common performance issues before they cause downtime or frustrate users. That alone makes it highly valuable for organizations.
But APM does more than help prevent problems—it also offers a roadmap for optimization. By providing visibility into how applications perform overall and under specific conditions (such as heavy load or network latency), APM can identify opportunities to further refine the user experience.
Observability is the ability to understand the internal state of a software from the data it produces. In other words, it’s about seeing exactly what’s happening inside a system or application, and making informed decisions to keep it running effectively. Observability involves analyzing information from various data sources—such as metrics, logs, and traces—to reveal not just that a problem exists, but also why it’s happening.
Observability is important because it speeds up the process of identifying the root cause of an issue, which can otherwise be resource-intensive and, if left unresolved, may lead to lost productivity or cybersecurity problems. It allows teams to detect issues early and understand their impact.
This helps ensure that every aspect of the identified vulnerability is addressed, while also allowing the business to make more informed decisions and proactively stay ahead of emerging risks instead of reacting to their consequences.
The key difference between Application Performance Monitoring and observability lies in the depth of insight they provide. APM tracks predefined metrics like page load times, API errors, and JavaScript failures, giving teams a clear picture of whether the application is performing properly. It’s good for detecting problems quickly—but it doesn’t always explain why those problems are taking place.
Observability, however, digs deeper. By gathering telemetry data from multiple sources, such as logs and user interactions, it empowers teams to conduct in-depth root cause analysis, revealing the true drivers of performance issues. This makes it invaluable for uncovering hidden bottlenecks or cascading failures that APM alone might miss.
In practice, APM simply tells you that something is wrong, while observability helps you explore the full story behind it.
Application Performance Monitoring and observability are both used for monitoring and optimizing application performance. They both rely on data to detect problems and provide visibility into how software behaves, which allows them to complement each other.
Where APM tools provide structured metrics that make it easy to identify performance issues, observability adds the ability to investigate those issues in more detail. It is therefore not uncommon for IT teams to use both APM and observability to gain a more complete picture of surface-level symptoms and deeper causes.
This overlap is especially evident when diagnosing complex performance problems. For instance, APM might flag slow page loads or high error rates, giving teams an early warning that something is not working correctly. Observability tools then allow engineers to trace those issues through user interactions, network calls, and backend processes to uncover the underlying cause.
Based on what we’ve established so far, you might be wondering what the practical applications are for using either APM or observability. While both help improve software performance, they serve different purposes and excel in different scenarios. The table below breaks down when to use each approach, so you can choose the right tool for the right situation.
Category | APM tools | Observability tools |
|---|---|---|
Problem diagnosis | Identify common errors and bottlenecks. | Investigate complex performance issues. |
Monitoring | Track specific performance metrics, error rates, and trigger alerts based on predefined thresholds. | Monitor overall health across distributed systems, underlying infrastructure, and services. |
Performance optimization | Pinpoint slow queries, inefficient code, or high-latency components within the app. | Identify systemic inefficiencies and cross-service performance bottlenecks. |
Incident response | Quickly detect known issues and review transaction traces to fix recurring errors. | Conduct in-depth investigations after complex incidents to uncover underlying issues. |
Deciding whether APM alone is sufficient or whether you need full observability usually comes down to the complexity of your IT environment. It also depends on the questions your IT team needs answered.
For relatively straightforward applications with a limited number of services and predictable performance patterns, APM tools can often meet your needs. It effectively tracks performance metrics, highlights slow transactions, and alerts you to obvious errors. For many teams, this level of insight is enough to keep systems healthy and respond quickly to common problems.
However, as applications become more distributed and dynamic—through microservices, serverless functions, or hybrid cloud setups—APM can start to show its limits. It tells you “what is happening” within individual services, but not why issues occur or how components interact. This is where observability comes in. It helps you uncover hidden dependencies and trace complex chains of events that might otherwise go unnoticed.
Another way to look at it is through your incident response needs. If fast detection of performance degradation or common errors is your priority, APM dashboards and alerts may be enough. But if you need to troubleshoot unpredictable anomalies or proactively optimize system behavior, observability provides the context required to do so.
Technically speaking, the term APM traditionally refers to server-side monitoring. However, when tracking in-browser performance, the industry instead relies on a specific APM sub-discipline called RUM, short for Real User Monitoring.
RUM is a form of passive monitoring that captures and analyzes user interactions directly within the browser. It focuses heavily on the end-user experience—for instance, tracking page load speeds across different devices or identifying where users experience latency on specific networks.
Observability takes this further by synthesizing data from RUM, server logs, and traces to provide a holistic view of the browser environment. While RUM shows what the user experienced, observability helps explain why it happened by correlating browser data with backend behavior.
More recently, observability has also been applied to SaaS and web security. By analyzing patterns such as domain visits, application usage, and data handling, observability tools help administrators identify security risks within the browser, including shadow IT, data exfiltration, and visits to sites that could lead to malware infections.
Even with strong network security—including VPNs, firewalls, and a Zero Trust approach—your business remains exposed at the most common entry point: the browser. Security gaps often emerge not from technical failure, but from risky user behavior and undetected web threats. The new NordLayer Browser is designed to help prevent those.
Alongside protections like Web Protection, Domain Blocking, and Browser Data Loss Prevention (DLP) elements—including download/upload controls, advanced clipboard (copy/paste) restrictions, and camera and microphone controls—NordLayer Browser also provides observability for administrators.
These tools allow you to monitor domain visits, extension usage, and other in-browser user activity, helping improve a safe browsing experience, limit shadow IT and unauthorized apps usage, and support compliance monitoring and reporting.
Crucially, this doesn’t compromise employee privacy. Observability tools highlight potential security risks and policy compliance issues without exposing personal or sensitive employee information.
If you want to improve your security posture and maintain regulatory compliance—without sacrificing user convenience or employee privacy—NordLayer Browser gives you the tools to do just that. See it for yourself.
Maciej Sikora
Senior Copywriter
A man on a mission to engage audiences with creative wordplay, Maciej knows every complex idea can be broken down into simple words—and that’s his driving force. When he’s not writing, you’ll find him making music, taking a walk with his dog, or watching yet another movie.
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