Software Code Audits Explained:
Processes, Benefits, and Best Practices

Bugs, security gaps, and messy structures are rarely detected during development. They often explode in production or accumulate over time until your codebase is a nightmare to work with. A software code audit can differentiate profitable software from an expensive failure.

A timely audit exposes problems while you can still act. It shows where your code performs too many unnecessary actions, where your security rules are half-baked, and which design choices will choke future updates.

In this article, we’ll go over the fundamentals of what a software code audit is and what different types of audits focus on. We’ll walk you through the full process, from finding hidden vulnerabilities to establishing a clear software code auditing process to keep your code and business secure.

A software code audit is an evaluation of your application for inefficiencies, clarifying issues, or security issues.

The goal is to understand the system’s current state and opportunities for improvement. Among other things, it should assess whether the software:

• Follows internal and external coding quality standards
• Properly handles errors and risks
• Supports stable performance under heavy loads
• Aligns with compliance and regulatory rules

A code audit is not the same as a code review. Reviews are usually short, focused, and constrained to specific parts of the code.

Compared to a code review, an audit examines the entire codebase and each of its components. It can take many forms, like a security audit that targets vulnerabilities or a performance audit that focuses on unnecessary complexities.

Depending on the function of the application being audited, code audits can look for different things.

A code audit breaks software code into understandable components and examines how each part works.

Architecture and boundaries

Reviewers look at the software as a whole, mapping the main modules, subsystems, and internal layers. A reviewer checks the boundaries of each application, how they delegate tasks, and how they exchange data with each other and external services.

A thorough review identifies hidden dependencies, poor design choices, and unclear ownership. For example, a tightly connected architecture makes it harder to update a single service, and a single issue can affect the whole system. In contrast, a modular system is much easier to maintain and scale.

Internal code structure

Auditors scan files and functions for inefficiencies, such as long methods, repeated logic, or hard-to-follow branching paths. It’s necessary to check whether the code tries to perform many actions at once or if it’s overly fragmented.

Defects like these may slow down code execution, debugging time, and subsequent updates. They become a prime target for developers to reorganize functions, remove dead code, and either unify or separate logic.

Testing and quality control

A software code audit should examine whether the test cases fully cover the key features and parts of the system. It’s important to see whether your development pipeline and automated tests catch issues early and prevent bad code commits.

Strong test coverage influences performance, reliability, and security. Irrelevant, out-of-date, and missing cases will make your software more vulnerable and will have your team dealing with the same bugs over and over.

Build, deployment, and configuration

Code audits include reviews of the operational side of your software. The goal is to ensure that the build uses clear instructions that always produce the same result and have a safe fallback if something goes wrong. Reviewers also check whether the application behaves properly in the development, testing, and production environments.

The audit highlights risks that may create unpredictable results and security issues. For instance, you can have a properly configured build and deployment with automated steps to keep your applications stable in new releases. At the same time, separated configuration data can reduce the chance of data leaks.

Data and error handling

Reviewers verify how the software processes users’ inputs and internal components. Every action taken by a user or internal process should be checked against the correct rules. It’s important to see how the system validates inputs, checks permissions, and reacts to errors.

These checks are a core part of the code security audit because you see if the software needs additional safeguards. Without strong validation or handling, malicious code inputs can cause unexpected behavior and leaks. Meanwhile, a lack of error handling will complicate troubleshooting and increase the system recovery time.

Documentation and onboarding

A source code audit assesses the setup instructions, architectural summaries, maintenance guides, and inline comments. Reviewers should also notice how often the documentation is checked and updated.

Proper documentation makes your entire codebase more understandable, explaining what the code does and why certain decisions were made. Missing or outdated documentation forces teams to rely on internal memory, which increases errors and makes onboarding difficult.

A code audit helps enhance your software products and internal services, making your business stronger.

A thorough audit can strengthen your entire software development lifecycle and products. Let’s cover all of the potential benefits.

Improved code quality and clarity

A code audit identifies opportunities to improve your code quality. Experienced reviewers can identify messy structure, inefficient logic, duplicate code, or lackluster documentation, among other things. Identifying and fixing these issues makes the code more understandable, reduces accidents, and shortens onboarding time.

Strengthened cybersecurity

Audits discover vulnerable parts of your source code, like poor input filtering, outdated dependencies, and weak authentication. If you patch them in time, you prevent data breaches, service interruptions, and costly downtime.

Compliance with privacy laws

A compliance-focused assessment reveals if your software handles personally identifiable information according to strict privacy laws. Auditors look at how you store, encrypt, share, log, retain, and control access to sensitive data. Meeting these requirements can help you get a respectable certification and avoid regulatory fines.

Lower long-term costs

Regular audits correct critical bugs, such as memory leaks, broken logic paths, and outdated libraries. These problems affect your services and user experience if they reach post-production. Timely assessments also correct rushed design decisions that increase technical debt, complicating further development and maintenance.

Fewer external risks

A third-party code audit ensures the reliability of your third-party components. Reviewers confirm that your libraries and components don’t contain unpatched vulnerabilities, external dependencies, licensing conditions, or other aspects that make your software more vulnerable.

Stable software performance

Auditors inspect the exact logic of your system, including database queries, memory usage, loops, network calls, and load distribution. After a codebase or website code audit, you can solve these bottlenecks. As a result, your product becomes responsive, resource-efficient, and reliable under heavy loads.

Better software scalability

Code audits confirm whether your software can handle more users, larger datasets, or new features without breaking. You can identify and address growth-limiting structural weaknesses, like tightly coupled modules, incorrect data queries, or single points of failure.

While code audits are expensive and time-consuming, you absolutely need them.

Code audits should be routine, but certain occasions can make them necessary. Consider the following as flags for a full-scale or partial assessment.

Pre- and post-launch

A code audit ensures new software products are safe, effective and compliant before market release. They are crucial for web applications before significant changes or launches. Running an audit shortly after launch helps catch issues missed during testing.

Ongoing software projects

Software accumulates technical debt as you add new features. Conducting audits helps clear the code from outdated logic and unnecessary dependencies as it grows. This proactive strategy also increases your users’ confidence in your digital product.

During performance issues

At some point, your software may suffer from the accumulation of technical debt, resulting in more errors, network lags, and crashes. An audit dissects how your code executes tasks, identifying reasons behind decreasing performance.

After security breaches

Breaches happen because part of your system had a weakness. Thorough security audits help trace the exact path hackers used to attack, find the root issues, and identify similar weaknesses elsewhere in the code.

Before integrating software

External payment gateways, third-party analytical tools, and other open-source components carry their own risks. You should check how your software interacts with these apps before and after integration.

In the case of onboarding

New team members may struggle to understand the codebase without proper documentation. Auditors can ensure the code logic is understandable and sufficiently explained in comments and annotations.

For mergers and acquisitions (M&A)

You inherit someone else’s software systems and technical risks when you acquire or merge with another organization. An audit will evaluate both companies’ technical readiness, code quality, and security posture, which are needed to estimate the potential optimization costs.

To prepare for the M&A, check our technology audit guide for IT due diligence. And if you want a full-scale audit, read further.

A full code audit can be daunting. Here’s how we divide it into stages and move through different sections of your software.

Step 1: Define the scope

Decide what parts of your software you want to examine. It’s best to keep the audit focused on high-risk areas instead of working across all parts of the system. You’re basically selecting what type of audit you want (security, performance, compliance, etc.).

After listing targets, map the supporting components behind them. For example, if you want to review the login flow, you should include hashing methods, session handling, stored tokens, database queries, and services that verify users.

Step 2: Assemble your team

Combine external and internal specialists. Even if you hire a source code audit firm, original developers will still help explain legacy decisions and business rules (especially poorly documented ones).

Assign roles and tasks early. One person may be responsible for the APIs, and another one can check how you store credentials. You should also have a senior engineer or manager who will make sure each area gets proper coverage.

Step 3: Review the code

Code audits usually include a series of reviews of your source code. This requires a mix of automated tools and manual checks.

Run automated tools to cover as many parts of the code as possible. Scanners will search the entire codebase for predictable problems, like style issues, unsafe database queries, and missing input checks.

Auditors should focus on the core logic and system behavior. They usually run through all key functions and check whether the code executes correctly and efficiently. This is where deeper issues appear, such as incorrect assumptions in the logic, inconsistent validation, and functions that run slower than they should.

Step 4: Document and report

Follow the reviews with a thorough code audit report that details results. Precise documentation is essential for the implementation phase. This comprehensive analysis usually includes the following:

• List of every issue found during the audit
• Impact of each problem on the software
• Highlights of the most critical problems

Reports should specify how to remediate these issues and how the system would behave after correction.

Step 5: Implement recommendations

Address the issues in any order you want. Of course, it is preferable that you prioritize high-risk problems that create the most bottlenecks or security risks. Then, proceed to secondary problems, like removing dead code, repairing broken error handling, or refactoring oversized files.

Teams often create patches in small, controlled steps to avoid breaking dependent features. After initial fixes, the code audit team retests the system to confirm  changes work under real conditions.

Step 6: Recheck and monitor

Periodic checks confirm that your fixes are in effect as you update the codebase. Engineers regularly review high-risk parts of the code, such as authentication, payment logic, and message handling.

Have a team that monitors the system logs regularly. Any deviations, be it performance spikes or crash logs, are easier to deal with quickly instead of waiting for the next scheduled audit.

It’s possible that you won’t need a full-fledged audit. You may focus on a specific aspect of your code instead.

Software code audits come in various forms and target different areas of the codebase. Knowing the types of audits helps you select the best one for your scenario.

Security code audit

Security code audits check if someone can break into your system by abusing weak spots in the code. Auditors review how users log in, how permissions are enforced, and how incoming data is cleaned. It also checks for known attack routes like SQL injection, cross-site scripting, unsafe file uploads, hardcoded passwords, or data-exposing API calls.

Performance code audit

A performance audit studies how efficiently your code uses the database, memory, and background operations. Experts look for excessive API calls, redundant data transformations, and functions that take too long to respond.

Compliance code audit

A compliance audit checks if your software follows data privacy laws, such as GDPR, HIPAA, and CPRA. It confirms that data is encrypted, that only the right people can view certain records, and that old data is promptly removed.

Code quality audit

A code quality audit looks at whether your codebase is clean and understandable. It looks for messy naming, repeated blocks of logic, huge files that do too much, and structures that complicate maintenance.

Infrastructure code audit

An infrastructure audit ensures your application runs in a reliable environment. Auditors check for misconfigured containers, exposed ports, insecure defaults, separation of business rules, and backup configurations.

To make a software code audit less overwhelming, you should follow a set of review practices and methodologies.

These practices make your audits more predictable and easier to follow.

• Integrate reviews into your pipeline. Make sure your scanners and checks run with every merge to catch issues as soon as they appear.
• Create customizable checklists. Standardize your review steps with a checklist that defines the essential areas for different types of code audits.
• Use internal and external knowledge. Your in-house engineers know how the product works, while external auditors spot patterns your team has grown blind to.
• Adopt the least privileged access. Develop each feature with the exact data and permissions it needs, so mistakes don’t accumulate across the entire codebase.
• Assign ownership and deadlines. Stakeholders should be responsible for each audit component or core issue and have realistic and concrete due dates.
• Maintain a knowledge base. Keep a shared database of detected issues and applied fixes, so the developers can learn from mistakes and avoid them.
• Double-check reports. Never trust an outside audit report or applied fixes until you can confirm them with tests.
• Plan audits as your software grows. As you add features and modules, schedule follow-ups to make sure the codebase remains healthy.

You can learn more in our complete guide to a software development audit. As for the last, we should also consider the tools you’ll need.

Tools can identify different components of your software, flagging problems and risks faster than you’d do manually. Below are the key categories of these code audit tools.

Static code analyzers (SAST)

Static analyzers check for mistakes without running the code. They help detect structural problems before regular software tests, primarily logic errors, insecure handling, or SQL injection risks.

Tools:

• SonarQube scans commits for duplicated logic, missing input checks, weak encryption calls, and more.
• Coverity traces data paths to find logic bugs, like inconsistent cross-function validation.
• Klocwork checks for issues in larger codebases and enterprise systems built in several programming languages and frameworks.

Dynamic code analyzers

Dynamic Application Security Testing and Interactive Application Security Testing test your software during simulations. They run real user actions, system inputs, and processing loads to capture how your code behaves under different scenarios.

Tools:

• JProfiler monitors memory allocation and thread activity in Java for slowdowns.
• YourKit tracks CPU usage and memory churn to expose inefficiencies, like poor caching or subpar algorithms.
• Dynatrace analyzes the runtime behavior of AI apps across distributed systems.

Fuzzing tools

Fuzzers throw huge amounts of malformed, random, or extreme input at your code. They reveal crashes, buffer overflows, and error paths that developers rarely test manually.

Tools:

• AFL (American Fuzzy Lop) mutates input files to trigger crashes and expose weak parsing logic.
• libFuzzer stresses individual functions with millions of variations to identify break points.
• Burp Suite Intruder sends volumes of custom payloads to APIs and other web endpoints to expose unsafe validation or routes.

Dependency scanners

Dependency checkers inspect external packages and libraries for vulnerabilities, outdated versions, risky licenses, and other risks.

Tools:

• OWASP Dependency Check matches dependencies against known vulnerability databases.
• Snyk monitors open-source packages and checks for weak libraries.
• Mend.io (formerly WhiteSource) identifies license risks and rule-breaking components.

Configuration and secret scanners

These tools look for security risks in the environment rather than the code itself. They can help find exposed secrets, weak encryption settings, unsafe configuration files, or misconfigured access rules.

Tools:

• GitLeak scans repositories for various issues, such as exposed passwords, tokens, or private keys in commits.
• TruffleHog can detect leaked secrets in file changes and commits.
• Checkov assesses infrastructure files for insecure defaults and rules.

Manual code review tools

Some tools simplify the manual review process. These apps and platforms can show changes, highlight risky lines, or track comments.

Tools:

• GitHub Code Review shows line-by-line changes and supports threaded comments to help coordinate the audit.
• GitLab Merge Requests integrate human code audits and reviews into CI/CD pipelines during the merge stages.
• Crucible helps track recurring issues and enforce coding quality standards.

A source code audit is still a human task that relies on skilled developers. As such, it requires a great deal of human hours.

Code audits can vary greatly in cost depending on various factors. Instead of numbers, we’ll describe the factors dictating the price:

• Goals and type: Security reviews, performance checks, and compliance assessments require different levels of scrutiny. An in-depth source code audit will demand vastly more resources and often grow in scope as you uncover problems.
• Codebase size: A larger codebase takes more time to examine. More lines of code do not always mean they’re harder to get through, but they increase the number of billed hours.
• Code complexity: A badly structured and poorly documented codebase needs a more careful code audit to untangle. Reviewers will spend extra time understanding how the system behaves and mapping all hidden dependencies.
• Existing coding standards: A code audit is much faster if the company follows clear standards with consistent naming, formatting, and documentation rules. Without these rules, the auditor must manually reconstruct how decisions were made.
• Compliance requirements: Industries with stricter regulations, such as finance or healthcare, require a comprehensible source code security audit that confirms the software meets all data privacy rules.
• Technical stack for audits: Some code audits require specialized tools for static analysis, dependency scanning, or compliance tracking. These may add licensing or configuration costs, especially when the system uses less common technologies.
• Team composition: Auditing teams in countries with higher living costs usually charge more, despite having no difference in skills from developers in other regions. Communication and time zone differences affect the efficiency of the audit process.
• Auditor payment model: The code audit company may charge based on time and materials or a fixed price. If you’re paying hourly, you can estimate the number of hours needed by the rate.
• Company’s expertise: The skill level of your auditing team is critical. For example, companies with experienced seniors find structural issues faster and detect subtle risks that less experienced reviewers may overlook.

It’s not a secret that a high-quality audit from a reputable firm can be expensive. But consider the financial impact of a company-wide data breach, fines from a regulatory body, and reputational damage from a massive leak. A timely source code audit saves you far more money down the line.

A good audit cleans up bugs and security issues. And, most importantly, it makes sure these problems don’t repeat.

It’s not enough to make sure your software meets your success criteria. Code audits should reveal whether you meet the demands of your industry. Otherwise, you’d find out about these bugs after pressure from clients, auditors, or regulators.

You need an experienced company with proven expertise in long-term projects across industries. One that knows what to check for and against and will then act on improving your software.

Want to make your software more stable, maintainable, and secure? Reach out to DevCom today for a targeted review or a full source code audit.