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Bug Severity: How & Why to Measure + Levels Guide

Last updated on
July 4, 2024


Bug severity in a nutshell

Bug severity in a nutshell: definition, benefits, risks


Bug Severity: How & Why to Measure + Levels Guide


Determining the severity of bugs is crucial for effective bug management and prioritization.

Developers often grapple with the impact bugs have on their software and struggle to decide which bugs should take precedence. They need a reliable method to measure bug severity and make informed decisions. By understanding bug severity, they can enhance software quality, prioritize effectively, and mitigate potential project risks.

In this article, you will explore the measurement, risks, and benefits of measuring bug severity. 

What is bug severity?

Bug severity definition

Bug severity is a measure of how serious a software defect is. It can help you prioritize and understand the impact of bugs on your software. 

Bug severity is like a scale that rates the impact of bugs. It enables your team to classify bugs into different levels based on their impact on the software's functionality. 

How to use bug severity in practice

By assigning severity levels to bugs, your team can prioritize their efforts. Critical and major bugs usually require immediate attention, as they affect the software's usability and reliability. Minor and trivial bugs can be addressed later, depending on the available resources.

Bug severity will allow you to focus on resolving the most critical issues first, ensuring a smoother software experience for users.

How do you categorize bug severity?

Bug severity levels

Severity is typically categorized into five levels:

Bug severity levels

Critical bug severity

These bugs have a severe impact on the software's functionality or stability

They often result in crashes, data corruption, or complete system failure, making the software unusable or causing critical data loss.


Imagine you're using an online banking application, and there's a bug that allows unauthorized users to access and withdraw money from any account without proper authentication. This is a critical severity bug because it has a severe impact on the application's security and can result in significant financial losses for users.

High bug severity

High-severity bugs are significant issues that can disrupt the normal operation of the software

They may cause important features to malfunction, lead to frequent errors, or pose security risks.


In a video conferencing software, a bug causes the application to crash randomly during important business meetings, disrupting communication and causing inconvenience to users. This is a high-severity bug because it significantly impacts the software's reliability and user experience.

Medium bug severity

Bugs with medium severity have a noticeable impact on the software's usability or functionality but do not cause critical issues

They may hinder certain features or workflows, but the software remains generally functional.


In an e-commerce website, a bug occasionally causes incorrect product images to be displayed on product listings. While this doesn't affect the core functionality of the website, it can confuse users and lead to potential purchasing errors. This is a medium-severity bug as it affects usability but doesn't render the website unusable.

Low bug severity

Low-severity bugs are minor issues that have little to no impact on the software's core functionality. 

They may include cosmetic issues, spelling errors, or non-critical user interface glitches.


A social media app has a bug where the notification icon occasionally displays a red dot when there are no new notifications. While this is a minor issue, it's still a low-severity bug because it doesn't affect the app's main features, but it can be slightly annoying for users.

Cosmetic bug severity

Cosmetic issues are the least severe and are typically related to the software's appearance or user interface. 

These bugs do not affect functionality but can impact the user experience by making the software look less polished.


In a word processing software, there's a bug that causes a minor formatting inconsistency in certain situations, such as a slightly misaligned text box. This is a cosmetic severity bug because it doesn't impact functionality or usability but affects the visual appearance of the document.

How to categorize bugs in practice?

Review bug details

Examine the bug report or issue description carefully. Look for information such as the bug's description, steps to reproduce, error messages, and any relevant logs or screenshots.

Assess impact on functionality

Consider how the bug affects the core functionality of the software. Bugs that cause the software to crash, result in data loss, or make essential features unusable are typically assigned higher severity levels.

Evaluate technical impact

Determine the bug's impact on the software's technical aspects - if it compromises security, introduces performance issues, or creates compatibility problems. Consider the long-term technical implications of the bug.

Evaluate User Experience

Think about the impact on the end-users. Bugs that lead to a poor user experience, inconvenience, or frustration are often considered more severe. User impact can include issues like usability problems, slow performance, or incorrect results.

Business impact

Assess the bug's impact on the business. Critical bugs that hinder revenue generation, disrupt critical processes, or affect compliance with regulatory requirements are usually given higher severity ratings.

Frequency and reproducibility

Determine how frequently the bug occurs and whether it is easily reproducible. Bugs that happen consistently and can be easily replicated are often considered more severe since they are more likely to affect a larger portion of users.

Isolation of the root cause

Understand how well the bug's root cause has been isolated. Bugs with a clear understanding of the underlying issue may be more straightforward to fix, but severe if the issue is critical.

Consider workarounds

Check if there are any known workarounds for the bug. If a simple workaround exists, it may lower the severity of the bug.

Consult with stakeholders

Discuss the bug with relevant stakeholders, including product managers, developers, and quality assurance teams. Gather different perspectives to make a well-informed assessment.

Apply severity level

Based on your evaluation, assign the appropriate severity level to the bug. Use the predefined scale to categorize it as Critical, High, Medium, Low, or Cosmetic.

Benefits of improving bug severity

Bug severity plays a crucial role in software development and bug management. By improving bug severity, you can enjoy several benefits that contribute to better software quality. Here are five key benefits of improving bug severity: 

Enhanced user experience

When you prioritize and fix critical and major bugs, you ensure that users have a smoother experience with your software. By addressing these severe bugs promptly, you prevent crashes, incorrect results, or functionality issues that may frustrate or inconvenience users. This, in turn, leads to higher user satisfaction and better adoption of the software.

Increased software reliability

Bugs with high severity can significantly impact the reliability of the software. By improving bug severity, you reduce the occurrence of critical issues that may cause the software to crash or stop working altogether. This leads to a more stable and dependable software product, instilling trust in users and minimizing disruptions in their workflows.

Efficient resource allocation

Bug severity helps prioritize your efforts and allocate resources effectively. By identifying and addressing critical bugs early on, you can allocate appropriate resources to fix them promptly. This prevents wasted time and effort on less severe issues, allowing your team to focus on the most impactful bugs and make efficient use of their skills and expertise.

Better risk mitigation

Critical and major bugs pose risks to the success of software projects. By improving bug severity, you actively mitigate these risks. You reduce the chances of encountering severe issues during production or in the hands of users, minimizing potential damage to the reputation of the software and the organization. Proactively managing bug severity helps you stay ahead of potential risks and ensures smoother project execution.

Increased development team productivity

By addressing bug severity effectively, you create a more productive environment for the development team. When critical and major bugs are resolved promptly, developers can focus on building new features and improving the software rather than firefighting severe issues. This boosts their productivity, motivation, and job satisfaction, resulting in faster software development cycles and overall efficiency.

Risks connected to focusing on bug severity

While measuring bug severity can be beneficial, it's important to be aware of the potential risks involved. Here are five risks that your product development team may face when basing their decisions solely on bug severity results: 

Neglecting user priorities

Relying solely on bug severity may lead to a myopic focus on technical aspects. It's crucial to consider user priorities as well. A high-severity bug may not always align with the user's needs or business goals. Focusing only on severity might result in overlooking less severe but impactful bugs that affect user experience and satisfaction.

Overlooking hidden bugs

Measuring bug severity may not capture all aspects of a bug's impact. Some bugs may appear less severe but can have broader implications. For example, a seemingly minor cosmetic issue may affect the overall perception of the software. Concentrating mainly on severity might lead to the oversight of these hidden bugs, impacting the overall quality of your product.

<span class="colorbox1" fs-test-element="box1"><p>Also read: Discover 8 technical debt metrics that help to track and address it, and compose your own set on that basis.</p></span>

Ignoring business impact

Severity alone does not consider the business impact of a bug. A bug may have low severity but significant consequences for the business, such as financial loss or compliance violations. Ignoring the business impact while prioritizing bug fixes based on severity can result in missed opportunities or legal and financial risks for your organization.

Inadequate allocation of resources

Focusing on bug severity can lead to inefficient allocation of resources. While critical bugs demand immediate attention, other important tasks, such as feature development or technical debt reduction, might be overlooked. Overemphasizing severity may strain development resources and delay other essential activities, impacting the overall progress and success of your project.

Demoralizing development team

Exclusively relying on bug severity might create a demoralizing environment for your development team. If developers are constantly firefighting high-severity bugs, it can lead to burnout and reduced motivation. The team may feel discouraged when they are unable to dedicate time and effort to long-term improvements and innovation. 

Alternatives to bug severity

Bug severity is an essential metric in bug management, but it's not the only approach. There are alternative methods that can be used alongside or instead of bug severity. Let's explore a few main alternatives: 

Bug priority

Bug priority focuses on the importance or urgency of fixing a bug based on factors such as business impact, user needs, and project goals. Unlike severity, which assesses the impact on functionality, bug priority considers the broader context and the relative importance of addressing the bug.

When to choose bug priority:

Bug priority is a suitable alternative when you have limited resources and a need to strategically allocate them based on business goals and user needs. It will help you ensure that bugs with high business value or critical user impact are addressed first, even if their severity may be lower.

Risk-based approach

The risk-based approach evaluates bugs by assessing the potential risks they pose to the software, users, and the organization. It considers factors such as financial impact, legal implications, security vulnerabilities, and reputational risks. Bugs with higher associated risks are given greater attention.

When to choose a risk-based approach:

The risk-based approach is valuable when you have specific risks that need to be mitigated or compliance requirements that must be met. It helps prioritize bug fixes based on the potential consequences and ensures that bugs with higher risks are addressed promptly.

User impact analysis

User impact analysis focuses on understanding how bugs affect the user experience and satisfaction. It considers factors like user feedback, support tickets, and user testing results to assess the impact of bugs on users' ability to achieve their goals and the overall user satisfaction.

When to choose user impact analysis:

User impact analysis is useful when your primary focus is to deliver a seamless and user-friendly experience. It will help you prioritize bug fixes based on their impact on user satisfaction and ensures that issues that significantly affect user experience are given priority, regardless of their severity.

Functional area priority

Functional area priority involves prioritizing bugs based on the criticality of different functional areas or modules within the software. Bugs in essential or high-traffic areas may be given higher priority, even if their severity may be lower, to ensure the smooth functioning of critical features.

When to choose functional area priority:

Functional area priority is beneficial when there are specific areas of the software that require special attention due to their criticality or impact on user workflows. It will help you ensure that bugs affecting vital functionality or core business processes are addressed promptly.

Next steps

Bug severity is a vital metric in software development that helps prioritize bug fixes and enhance software quality. By measuring bug severity you will prioritize bug fixes effectively, resulting in improved user experience and software reliability. This metric also plays a crucial role in successful product development and scaling. 

Explore additional software development metrics in our articles to compose a comprehensive set of metrics tailored to your specific product and needs.

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Olga Gierszal
IT Outsourcing Market Analyst & Software Engineering Editor

Software development enthusiast with 7 years of professional experience in the tech industry. Experienced in outsourcing market analysis, with a special focus on nearshoring. In the meantime, our expert in explaining tech, business, and digital topics in an accessible way. Writer and translator after hours.

Olga Gierszal
IT Outsourcing Market Analyst & Software Engineering Editor

Software development enthusiast with 7 years of professional experience in the tech industry. Experienced in outsourcing market analysis, with a special focus on nearshoring. In the meantime, our expert in explaining tech, business, and digital topics in an accessible way. Writer and translator after hours.

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