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Application Logs: What They Are and How to Use Them

Within software development, application logging plays an important role. As much as we’d like our software to be perfect, issues will always arise within a production environment. When they do, a good logging strategy is crucial. But what is application logging? How should you be using application logs? Where can you find them? And what does all this mean for your own logging strategy? We’ll take a look at each of these questions in this post.

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What Is Application Logging?

Put simply, an application log is a file that contains information about events that have occurred within a software application. These events are logged out by the application and written to the file. They can include errors and warnings as well as informational events.

What Does an Application Log File Include?

The types of information and format of messages found in an application log file will vary by application. This is because these variables aren’t determined by external guidelines or by the operating system. Rather, the developers of the software application control what goes into the log file. They’re the ones making decisions about what events and information would be useful to log and how it should be done. Many events will be specific to the source application. However, it is common for logged events to contain certain pieces of information to make them more useful. Here are some common components that you will generally find in application log messages:

  • Context information: Background information that provides insight into the state of the application at the time of the message.
  • Timestamps: A specific piece of contextual information for tracking and correlating issues.
  • Log levels: Labels that help you calculate the level of importance for the entries in your log file. Frequently used levels include INFO, WARN, and ERROR.

Becoming familiar with logged messages will make it easier to use them when you’re trying to analyze bugs and unexpected events.

What Application Logging Isn’t

When developers use the word “logging,” they’re usually referring to application logging. However, other types of logging exist as well. To help further clarify what application logging is, we’ll briefly look at other types of logs to help understand the distinction.

  • System logs are written by the operating system. They contain information about drivers and system processes. On a Windows machine, the event log stores these; in Linux, this is the syslog service.
  • Server logs provide information on the state of a web or application server. The server is responsible for creating and maintaining server log files.
  • Garbage collector logs assist with memory management by tracking objects within a JVM and removing those that are unused. They are deactivated by default.

Where to Find Application Logs

Now that you know what an application log is, you’ll want to know where to find them.

Finding Logs From Other Applications

To find application logs on your local computer, check the following locations:

  • On a Windows computer: Inside the Control Panel, find System & Security. From there, go to Administrative Tools and then the Event Viewer. Open Windows Logs and choose Application. This will show you all the application logs saved on your computer.
  • On a Mac computer: Inside your Applications folder, you’ll find a Utilities folder. Open Console and locate “/var/log” and expand to see if the application you’re looking for is inside.

Storing Your Own Application Logs

If you’re trying to decide where to store the application logs of your own software, avoid manually writing logs to a local console. Instead, use a logging framework, which will keep your logs in a secure location and take care of standardization across your platform.

How to Send Application Logs

Once you’re using a logging framework, the task of sending logs becomes relatively simple. In most cases, there will be an HTTP endpoint that you can use to write log messages directly. The specific implementation details will vary depending on the specific framework you use. You’ll need to ensure that it functions well with your software prior to making a final decision.

How to Use Application Logs

As mentioned above, application logs are incredibly useful when it comes to solving bugs and troubleshooting issues within an application. We briefly looked at what kind of information a log file can contain, but how can we use that information to solve problems that arise?

The first step is becoming aware that there is a problem. This can be based on manual observation, notifications from customers, or automated alerts from a log management tool such as XpoLog. With a log management tool, it can even be possible to discover an issue before it occurs by monitoring log patterns.

Regardless of how you discover the issue, the next step is to figure out what caused it. You’ll need a way to search through your log files to find the relevant messages. This can be the error event itself or events that occurred around the same time. This is where timestamps in logs will prove to be very useful, as well as standardization of the message format for efficient searching.

Once you’ve located the relevant log messages, you’ll need to analyze them so that you can understand the problem and the state of the application at the time the issue took place. The contextual information included in the logs should provide enough information to locate the cause of the issue quickly in order to solve it with minimal effect.

Why Is Application Logging Important?

There are two main reasons why application logs play an important role in your overall strategy: diagnostics and auditing.


Diagnosing issues is the most common reason for utilizing log files. In the previous section, we described how to use application logs to discover and solve bugs in a production environment. This process takes place regularly during software development. It’s critical to the long-term optimal performance of an application.

Another way to use application logs for diagnostics is by tracking and correlating certain information and using it to perform analytics on your software. Some examples of information that might be useful to track and analyze are customer transactions, security threats, timeouts, and consumer behavior. This is where log management tools become really useful, ensuring you don’t miss out on any of the valuable insights that can be gained from the information you’re already collecting.


Application logs can also be used for auditing purposes. These logged messages involve significant events in the application as well as information relating to management and finance. This information may not provide as much benefit on a daily basis, but it’s important for fulfilling business requirements.


In this article, we’ve defined application logs, discussed how to find and send them, and described the ways that you can use application logging. Hopefully, you’ve been convinced of its importance within your organization as well. Application logging will help you discover and solve issues quickly, understand your application’s performance, and stay up-to-date with business requirements. To fully take advantage of these benefits, however, you’ll eventually want to move away from manually reviewing log files and incorporate a log management tool into your strategy. XpoLog provides a number of ways to maximize the usefulness of your logs. These include automated log analysis, real-time log monitoring, log correlation and search, and automated log parsing. Request a demo or try it for free to start getting the most out of your application log file.

This post was written by Delila Lee. Delila s a software developer in the NLP and ML space with degrees in both linguistics and computer science. She currently works with functional programming languages, and she does some web development on occasion.

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