Automated Code Review Vs Manual Code Review


What is Code Review?

Code Review is an integral process and an ongoing practice during the software development phase. It helps to identify defects and bugs before the testing phase. It is an agile process where pieces of source code are made available to the peers for inspection with an aim to catch bugs, highlight mistakes, remove vulnerabilities before they form a part of the product.

Code review is a two-way conversation where both the author of the code and its reviewer communicate and learn from each other. Thus it can also be thought of as a knowledge-sharing process.

Why Code Review?

Firstly, Finding bugs early in the life cycle is always less expensive. Sooner the better. Infact, a post product bug cost may be 30X more than its cost if found during the coding phase. 

Relative cost to fix bugs based on the time of detection

Secondly, code review would help visualize aspects of the code that may otherwise go unnoticed.  This way a team can get a holistic view of quality and be able to identify the problems better.

Manual and Automated Code Review

In a Manual Code Review (MCR), the source code is read line by line to check for possible vulnerabilities. This involves a lot of skills, experience, and patience. The issues or errors discovered in this review will greatly help to increase the efficiency of the firm.

With an Automated Code Review (ACR), there is a set of predefined rules that are determined for the code to comply with. Software tools provide assistance in ACR that displays a list of warnings that are in violation of programming standards.

With automation, software tools provide assistance with the detection process. This is what makes it easier by improving the entire process by providing an automated or a programmer-assisted way to correct the errors found. This is a component for mastering Software Development Tools.Software tools provide assistance in ACR that displays a list of warnings that are in violation of programming standards.

So how to decide which works best for you? Here’s a comparison that we thought would help you make this decision.

Differences Between Manual & Automated Code Review

Manual code review vs automated code review
Fig: Manual Code Review vs Automated Code Review

1) Time:

MCR – Because the user reads every single line of the code, it is easy to gather the intentions of the developer. But even if that is the strength, it takes a lot of time to look and read these codes line by line.

ACR – No wonders it’s fast! Automation software can read thousands of lines of code very swiftly. But these lack the skills of identifying the business logic and the intentions of the developer.

2) Examination:

MCR – This method is very useful in crossing the rarely visited code paths. Few techniques such as penetration testing examine paths that have inputs fed, but lesser-traveled paths or hidden paths can be missed. But a rigorous manual code review is better in identifying these paths that are misunderstood by automated tools.

ACR – These intentionally hidden paths can also be easily explored by automation tools that are much more sophisticated but the automated code review can miss the intentions behind these.

3) Subtle Mistakes:

MCR – Because the reviews are done by reviewers on an individual basis, it is very possible that the human eye can miss a few vulnerabilities that are related to integration or other isolated problems.

ACR – These mistakes and small errors that are missed in manual reviewing are easily caught by automated systems. However, this automation cannot go beyond a particular limit of reviewing which can be done by manual code review.

4) Costs:

MCR – Having trained and skilled engineers to handle an efficient manual code review comes attached to its obvious costs. It takes years of experience before a reviewer is able to adequately able to manage reviews.

ACR – It isn’t necessary for reviewers to have the entire knowledge and skills of reviewing. The automation software is programmed to issue warnings of potential errors. ACR does require development skills to set it up.

Pravin Uttarwar, CTO of Mindbowser Group

At Mindbowser, I and my CEO teamed together to build an agency that can bring the best of tech and knowledge for founders.

In case you would like to discuss your options further, feel free to get in touch at or book a 30 minutes free consultation call!

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Both these methods of review have their own pros and cons. Thus we understand the difficulty in choosing which one to go ahead with. Generally, the trend is now shifting towards automated code review because of time, cost, and effort but still, many companies prefer to have a human touch to it.

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