Imagine you need to buy a thermos flask from the local shop. The first thing you would probably pay attention to is its features. You may go for a flask with two serving cups to be able to share your drink with a friend. But hold on a sec, that’s not all!. You should also check whether this flask can keep your drink hot for at least 12 hours, since pouring cold coffee into even the most convenient cup won’t be satisfying in any case. 

In the software development world, the flask features would be called functional requirements, while its ability to keep beverages warm would relate to non-functional requirements. Just like choosing flasks, you have to consider both of these types of requirements in the planning stage of your software project, as they will determine how your product will perform in the long run. 

In this blog post, the JatApp team will give you an overview of functional and non-functional requirements and teach you how to write them correctly. Without further ado, let’s get started.

What is the difference between functional and non-functional requirements?

Functional requirements define what users should be able to do with a software product, while non-functional requirements describe its quality attributes. For instance, the functional requirement for a website would be the search feature, while the non-functional requirement would be that the search functionality should respond to user queries within three seconds. Find more examples of functional and non-functional requirements in the picture down below. 


functional and-non-functional requirements


Functional and non-functional requirements offer teams a full set of standards that help the team build a secure product that performs well. They serve as a reference point organizing team members around an end goal and allowing them to plan, prioritize, and communicate their work more effectively. Without either type of requirements, teams feel unsure what kind of software system they need to deliver, which leads to missed deadlines, cost overruns, inadequate communication, and shattered nerves. In the end, you’ll receive a poorly performing solution, which users need as much as ugly Christmas sweaters on the Spring break. 



Getting a closer look at functional requirements

functional requirements


Functional requirements can be categorized based on different tasks that product features are expected to complete. For you to get an idea of the types of functional requirements, let’s take any e-commerce website as an example.

  • User management 

This requirement outlines how the solution should manage user accounts, like enabling users to reset their passwords, edit profiles, and similar.

  • Search and filter

The given requirement shows how users can search and filter the content within the app. The solution may allow them to filter by price or category, or search for relevant products by typing in the name. 

  • Product catalog

The following type of requirement explains how the product catalog should be managed, like enabling admins to edit product descriptions, add or remove products, and so on.

  • Payment

The payment requirement specifies the checkout and payment process, such as allowing users to enter shipping details, add items to their carts, select payment methods, and stuff like that. 

  • Notifications

The notification requirement shows how the solution will alert users of important updates. For example, it could be sending notifications when the product is out of stock, an order is processed, or the account is about to expire. 

  • Reporting and analytics

This type of functional requirements show how the solution will generate reports and analytics on different relevant metrics, like, for instance, monitoring user engagement or generating revenue reports. 

Why are functional requirements important for project managers?

Project managers can’t afford skipping functional requirements and here’s why:

  • They help with project planning

Crafting functional requirements lets project managers gain a helicopter view of the project scope, as well as time and resources needed. These requirements lie a solid basis for product roadmaps, team schedules, budget estimates, and other important project management docs.

  • They allows to better monitor the project

Having outlined all functional requirements, a project manager can better control how the project is progressing, putting a tick after each feature being successfully released. Tracking the progress against requirements allows managers to spot different risks and timely take action if needed. 

  • They ensure effective communication

Functional requirements help project managers to keep an open dialogue with stakeholders regarding the project’s goals, scope, and progress. With functional requirements, everyone knows what is expected of them and how to prioritize their work to achieve common business goals. 

Going beyond the surface: Understanding non-functional requirements

non-functional requirements


Teams often place too much focus on functional requirements, while ignoring or not paying enough attention to non-functional ones. As a result, the final product doesn’t work as intended, making users annoyed, overwhelmed, and even distressed. 

A good project manager always has to consider common non-technical requirements along with functional ones, such as:

  • Performance

The performance requirements specify how fast your software solution is. Simply put, they outline how much time a user will have to wait for the app to respond to their action. 

Example: The app must be able to simultaneously handle 15,000 user requests with the response time no more than four seconds per one request. 

  • Security

The security requirements show how well the data in the app is protected from the prying eyes. This type of requirements act as a reference point explaining to software developers what industry standards they need to follow to deliver a 100% secure app.

Example: The fintech solution must be Payment Card Industry (PCI) compliant. 

  • Scalability

This type of non-functional requirement suggests the highest workload under which a solution will function without compromising its performance. 

Example: The solution must be able to handle a 40% traffic increase within 24 hours without facing any performance issues. 

  • Maintainability 

The following requirement explains how software must be designed to make it easier for software engineers to change, fix, and update it in the course of time. 

Example: The source code must adhere to industry-standard coding conventions, such as code formatting, naming conventions, and documentation.

  • Portability

This non-technical requirement demonstrates how easily a software solution can run on various platforms. 

Example: The app must be portable across Windows and macOS. No code modifications will be necessary for this application to be compatible with these operating systems.



Why do project managers care about non-functional requirements?

Without non-functional requirements, project managers would have to deal with constant rework or even worse – security issues. Let’s discuss how exactly managers benefit from having non-functional requirements in place. 

  • They help to release on time

Non-functional requirements allow team members to write the code that meets stakeholder expectations and avoid lots of bug fixing. As developers don’t have to make many changes to software all the time, project managers can successfully meet the project deadlines. 

  • They make it easier to stay within budget

If the team skips the requirement setup and spends more time on quality assurance, project managers will have to charge the client for extra work. Failing to stick to the initial budget may question the competence of the entire team, which is the last thing a good project manager will want to deal with.  

  • They ensure that a software system performs as expected

Building software without non-functional requirements will feel like climbing a mountain with rocks on the back. Constant performance issues will become a heavy burden at some point, making the entire software development journey long and exhausting. By contrast, specifying how an app should perform sets concrete standards that the whole team should strictly follow. Setting specific rules and goals makes it easier for the team to build the product that lives up to stakeholders’ expectations. 

  • They keep security risks to a minimum

Managers that omit security requirements are making a huge mistake, as they jeopardize the most important thing that they have – users’ trust. Hackers can easily take advantage of a solution with security issues, stealing users’ sensitive data. After such an incident, it would be increasingly challenging to restore your brand reputation in the eyes of the customers.  

Tried-and-true best practices on how to write functional and non-functional requirements


best practices


To build a solution that meets users’ needs and functions properly, you need to know how to write your requirements well. The tips below could be an ace up your sleeve that would help you to create clear and comprehensive documents. 

  • Identify the needs of all stakeholders

Before jotting down any requirements, it’s important to talk to all stakeholders in order to understand what they expect from the final product. To identify their needs, you may try such proven techniques as interviews, user surveys, or focus groups. 

  • Prioritize requirements

You’ll also need to prioritize your requirements in terms of urgency, importance, and feasibility. In such a way, you’ll be able to tell which requirements are within the scope and which are not. 

  • Use clear and concise language

As any document in your project, the requirements should be written using clear and concise language. Both functional and non-functional requirements should be easy to understand for all team members, including developers, designers, and quality assurance specialists. 

  • Define acceptance criteria

The requirements document was born to help avoid confusion and miscommunication in software development. So, if your team is puzzled not knowing whether they met a certain requirement, this document doesn’t fulfill its main purpose. You should always define acceptance criteria for teammates to clearly understand when they can close the task and when they can’t.

  • Use feedback loops

Rely on feedback loops to gain insights from stakeholders. These findings will help you to not fall victim to your cognitive biases and better understand other stakeholders’ thoughts on how the product should function.

  • Don’t forget to update

Review and update your requirements on a regular basis to make sure they stay relevant during each stage of the development process. 

Trust your requirements to JatApp

Without functional and non-functional requirements, you’re likely to lose lots of money and time that you could have spent on improving your product even further. And your development team and project managers…Poor, poor them – building the product they can’t even envision is like squeezing juice out of bananas. Each sprint you’ll request another change to your software, and there is no guarantee it will differ from the previous ones. It already sounds tiring, so we would highly recommend you save some time and come up and care about the requirements in advance. 

If you take your requirements seriously, the scenario we’ve just imagined may never become a reality. And JatApp is always here to help you with your docs. With nearly eight years of experience, our software agency has strong knowledge of how to properly craft requirements and deliver a solution that meets the needs of all stakeholders. Our attention to detail and result-oriented approach has enabled us to set up requirements for more than 200 startups and big companies, making us the top managed service provider according to Clutch.

So why wait? Contact us today and let’s get started on your requirements!