Client-side logging for modern web applications

Over the past decade, application logic has shifted from the backend to the frontend. In the past, developers would set up backend logging systems to understand system errors. However, most modern applications are now built with extensive frontend logic to support highly reactive and responsive user interfaces.

With more logic on the frontend, there is an increasing need for frontend observability. Frontend observability refers to the practice of monitoring and understanding how users experience your application by capturing client-side logs, performance data, and other relevant information directly from their browsers.

Client-side logging plays a vital role in frontend observability by helping developers identify issues, enhance user experience, and improve overall application performance.

Data to collect in client-side logging

In backend logging, it’s pretty clear what you want to capture: error messages, system logs, and HTTP requests and responses, to name a few examples. On the client side, deciding what data to collect is much more challenging.

You need to determine what data will be most useful and how to gather sufficient information to troubleshoot issues without overwhelming your team, impacting your application’s performance, or infringing on user privacy.

In our experience, the most sophisticated frontend teams capture:

• All console messages: Console logs, errors, warnings, and other messages provide valuable context about bugs or issues that occur during JavaScript code execution
• HTTP traffic from the browser’s perspective: Insights into issues like failed third-party requests can help you identify bottlenecks or problems with external dependencies
• DOM state over time: Tracking changes in DOM elements can reveal hidden bugs or performance problems
• Performance data: Information such as CPU and memory usage can help you optimize resource consumption and improve overall performance
• User context from the session: Understanding user demographics — device type, browser version, location, and more — can help you identify issues occurring for particular cohorts or tailor your application to specific target audiences

By collecting this data, developers can gain a comprehensive understanding of their application’s real-world performance and address issues before they escalate.

How to collect client-side logging data

There are two primary methods for collecting client-side data:

• Forward data from the UI to your backend log collection tool: This approach allows you to integrate client-side logs with existing logging infrastructure but may require additional development effort and increase server load
• Use a client-side logging tool like LogRocket: Dedicated client-side logging tools provide out-of-the-box functionality for capturing and analyzing frontend logs, including features like automatic error tracking, session recordings, and advanced filtering capabilities

Consider your team's familiarity with existing logging tools and weigh each option’s potential benefits and challenges to determine which method is best for your particular needs.

Use cases for client-side logging

Client-side logging can provide valuable insights into various aspects of your application's performance and user experience:

• Reproducing bugs: Detailed logs help developers identify the root cause of issues and reproduce them without having to deal with time-consuming back-and-forth exchanges with users, which can be frustrating for both sides
• Proactively surfacing issues: Monitor frontend logs to discover potential problems before they escalate or impact users
• Understanding user behavior: Identify patterns in user interactions to inform product design, feature additions or improvements, and other business decisions

You can use client-side logging data to improve your application’s performance and provide a smooth digital experience for all users.

Key features to look for in a client-side logging tool

A good client-side logging tool should provide features that help you efficiently analyze and resolve frontend issues:

• Configurable data capture: Too much data can be noisy to monitor and expensive to ingest. The best tools should enable you to configure exactly what data to capture based on your specific needs

• Robust search and filtering capabilities: Quickly locating relevant logs or sessions is crucial for efficient debugging and issue resolution

• Session replay: See exactly how your users experience your application for the valuable context you need to prioritize and troubleshoot high-impact issues

• Issue aggregation: Tools that automatically group similar issues can help you prioritize fixes and reduce noise

Remember that client-side logging solutions are not all created equal. Some may show you what happened but lack the technical telemetry to help you figure out why. Others may add to the noise instead of cutting through it, or have a steep learning curve that prevents teams from collecting useful insights right away.

To get maximum value from your client-side logging tool, you need a comprehensive solution like LogRocket.

Why LogRocket for client-side logging?

LogRocket is easy to set up and use, with little to no impact on performance. With one line of code, your whole team can get onboarded quickly and start using LogRocket as a single source of truth for the essential data you need to improve your application.

By collecting all your frontend telemetry — including client-side logs and all the code-level detail — alongside a high-fidelity session replay, LogRocket allows you to see exactly what users experience and the technical context regarding why.

Additionally, you can browse, search, filter, and analyze JavaScript errors affecting your users. You can also quantify the impact and reach of an issue, such as the key business goals or total users affected, helping you prioritize fixes based on their severity.

Moreover, LogRocket’s Galileo machine learning module automatically identifies, aggregates, and rates the severity of JavaScript errors and other issues. You’ll receive alerts for severe issues that actually affect your users rather than a high volume of false positives. Based on over a billion user interactions, LogRocket Galileo will leave you confident that you’re spending your time on the most impactful issues affecting your users.

Leveraging this data promotes cross-team collaboration and faster issue resolution. Find JavaScript errors impacting your goals, watch user sessions to understand their effect on UX, then route alerts and errors to the appropriate team member for a fix.

Try LogRocket yourself for free!

Client-side logging is an essential aspect of modern web application development that helps improve frontend observability and deliver better user experiences. LogRocket can help you proactively identify and resolve issues while optimizing your application for real-world usage.

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