How to Monitor Frontend Memory Usage

First of all, by frontend memory usage I mean the amount of memory that a user’s browser needs when using your website or webapp.

Secondly, do you have any idea how much browser memory your website or webapp requires? Or do you know if or how much the memory footprint of your website/webapp has changed over the last few months? Or after the recent changes or releases you made?

I’m guessing you don’t. Yet, this is important to monitor to avoid a bad user experience.

In this article we’ll go over:

• Common causes of memory usage jumps
• How to monitor and get alerted about an increased memory usage in production
• How to detect memory usage jump early, as part of your CI/CD
• How to utilize logs to dig deeper into causes of failures

Imagine a case where you’re responsible for keeping a website fast and smooth. You’re regularly updating the code, removing outdated libraries, swapping in better alternatives, or just keeping things up to date. All these changes are necessary—but they can also affect how the site performs.

Memory usage – as in memory a web browser uses when on your website – is one of those things that can quietly creep up. A third-party plugin might become heavier after an update. A new library might not be as efficient as expected. Or small changes in the codebase might slowly increase memory consumption. Over time, these things add up.

Websites that use too much browser memory can become sluggish or unresponsive, which hurts the user experience and, in some cases, even business outcomes. That’s why it’s important to monitor how memory usage changes over time. It helps you spot when performance starts to degrade and lets you relate those trends to specific code changes or updates. For example, by sending deployment events to your observability platform you can quickly see if a particular release is behind a spike in memory usage.

With that kind of visibility, it’s easier to make informed decisions — whether to roll back a change, replace a dependency, or dig deeper into what’s causing the spike. It saves time and helps keep your site running smoothly, no matter how much it evolves.

What Causes Website Memory Usage to Increase?

There are several reasons for why your website might experience increased memory usage over time:

• Memory leaks
• Problems within the code
• Problems within the libraries which are used
• Problems with third party scripts and plugins

Memory leaks
Memory leaks happen when code keeps allocating memory without releasing it, slowly using up available resources. These usually affect individual sessions, but in this post, the focus is on tracking overall memory usage over time. If you’re looking for more on memory leaks and how to detect them, we’ve covered that in a separate blog post.

Inefficient code
New features often increase memory usage, but sometimes code is added or updated in inefficient ways. Tracking memory usage over time helps you spot when things changed and makes it easier to identify and optimize the parts of code causing problems. You can narrow down the root cause even more by sending deployment events that include metadata like a commit hash or release tag. This lets you tie memory usage changes directly to specific code changes and investigate more efficiently.

Issues with libraries
Libraries are great for speeding up development, but they can also introduce performance issues, especially when they’re outdated, replaced, or updated. By correlating memory usage trends with specific releases, you can quickly identify if a new or updated library introduced a performance regression. For example, sending a deployment event that includes the updated library version can help you pinpoint exactly when the issue began.

Third-party scripts and plugins
Scripts and plugins from third parties can introduce memory issues that are hard to trace. Since you don’t control them directly, identifying the source can be tricky. Monitoring, and especially the kind that clearly separates performance from scripts and plugins that are not from your own website/domain, helps rule out other causes and narrows down what might be going wrong.

How to Detect Website Memory Usage Problems?

Now that we’ve looked at what can cause memory issues, let’s talk about how to detect them. The most effective way is by using an automated monitoring tool that regularly checks your website and tracks memory usage over time.

Synthetic monitoring tools do this by simulating real user interactions, visiting your site, running predefined scripts, and collecting performance data. This makes it easy to spot trends as well as sudden anomalies, catch issues early, and understand how changes impact memory usage.

Now, let’s walk through how to do this using Sematext Synthetics.

How to Monitor Website Memory Usage Over Time with Sematext Synthetics

Before we dive into the setup, here’s what you can expect once this is up and running:

• A live and historic memory usage chart that helps you spot spikes and regressions over time
• Correlation between memory metrics and code deployments or library updates
  
• Alerts for memory anomalies or usage thresholds being crossed
• The ability to drill down into logs and identify the root cause of memory problems
• Integration into your CI/CD pipeline to catch regressions before production
  

Now, let’s look at how to set this up using Sematext Synthetics.

1. Login to Sematext Cloud and create a Synthetics App. Set up a Browser or HTTP Monitor
   Use Browser Monitors to simulate full user journeys such as login or navigation etc., and HTTP Monitors for checking individual endpoints like API health or load times. You can configure these monitors to run at your preferred interval, such as every 5 or 10 minutes etc., depending on how frequently you want to track performance.
2. Extract heap usage metrics
   In each monitor run, extract memory-related metrics such as heap size.These metrics are stored with each run and can be used for visualization or alerting.
3. Create a Dashboard to visualize memory usage
   Create a Dashboard and build time-series visualizations using the heap usage metric to track changes over time.
4. Set up alerts for heap usage
   Create threshold alerts (e.g., notify if heap usage exceeds 300 MB).
   Configure anomaly alerts to catch unusual increases in memory that deviate from normal trends.

Send alerts to various Notification Hooks such as email, Slack, or incident management tools like PagerDuty, AlertOps, OpsGenie, etc.

Correlate Memory Usage with Deployments

If you’re serious about understanding and fixing memory regressions, sending deployment events to Sematext is essential. Without this, you’re kind of limited. There’s no reliable way to connect changes in memory usage to the exact release or commit that caused them.

We recommend using the Sematext API to send deployment events during every release. Include key metadata like the environment, version number, or commit hash. Then, to correlate changes in memory usage – or really any other piece of telemetry data – use the Split Screen to view the deployment timeline alongside the memory usage chart.

This helps you quickly see whether a specific deployment caused a spike in memory usage.
Or, if you spot a memory spike, you can check whether it aligns with a recent deployment. The screenshot below does not show any memory spikes, but you can see browser heap memory usage on the left half of the screen and various events on the right half.

Monitoring Memory Usage in CI/CD Pipelines with CI/CD Monitors

In addition to continuous monitoring in production, memory usage can be tracked earlier in the development cycle using CI/CD Monitors.

These monitors can be integrated directly into your CI/CD pipeline, enabling you to test browser memory usage automatically before changes reach production. For example, you can have monitors run on every pull request or push to GitHub, allowing you to observe heap usage as part of your pre-release testing.

This helps you catch not just memory footprint regressions, but also other types of performance regressions introduced by new code early in the development cycle.

To learn more about how to set up CI/CD Monitors, check out our step-by-step guide, including GitHub workflow examples.

Digging Deeper: Use Logs to Investigate Root Causes

Monitoring memory usage is a great starting point, but sometimes you need more context to understand why something changed. That’s where application logs come in.

Sematext Cloud includes a Logs solution that lets you collect logs from your website’s codebase. By adding logging to your application and shipping those logs to Sematext, you gain deeper visibility into what’s happening behind the scenes.

Here’s how to go further in your investigations:

• Collect logs from your frontend application
  Use Sematext’s Custom Integrations to send logs from your website’s code (e.g., JavaScript in the browser, or any backend language you’re using).
• Connect your Synthetics and Logs Apps
  Use the Connect Apps to link your Synthetics App (used to monitor heap usage) with your Logs App (used to collect logs). This allows for cross-correlation between monitoring data and logs.
• Access logs directly from monitor run results
  For failed Synthetics runs, you can go to the Troubleshooting section and immediately access relevant logs for that time window. This makes it faster to identify patterns or isolate problematic code paths.
  
  

By combining Synthetic Monitoring with log analysis, you get a full picture — not just when something breaks, but why it did.

Conclusion

Monitoring browser memory usage is essential for maintaining performance and stability — especially as changes accumulate in your codebase. Sematext Synthetics simplifies this by automating the entire process, from collecting memory metrics like heap usage to triggering alerts when thresholds are exceeded.

With consistent data collection over time, you can easily detect trends, spot regressions, and tie memory spikes to specific deployments. Sematext also supports simulations across different devices and global locations, helping you understand how your site behaves for all users — whether on mobile, desktop, or from various regions.

More than just memory tracking, Sematext Synthetics is part of a broader observability platform that integrates logs, and metrics. This gives you full-stack visibility and the tools to quickly detect, investigate, and resolve issues — all in one place.