software requirements document

How to write a software requirements document?


What is a software requirements document?

A software requirements document, or a software requirements specification, is a detailed description of a software solution (mobile or web application, website, or software system) a customer wants to develop.

Also, this definition means a kind of agreement between you and a software development company that helps you meet financial objectives as well as allows both you and app development team to clearly understand project tasks, goals, and technical part as well.

Preparation of SRS is the first stage of any project. Generally, it starts with collecting and processing customer’s requirements, and once it’s made, a software development team writes a specification.

Surely, in some cases, a software requirements document is totally prepared by client’s technical specialists, but generally it’s made by our developers: we receive business tasks the product should complete, requirements to the product appearance, or just its idea. So, here our business analysts get involved in the stage and solve all the issues, helping to create a perfect technical specification.

To write a software requirement specification is a difficult task as you need to take into account various things and really “delve” into the product: which challenges it will solve, which features it will need, how it will work, what is your target audience, how many screens or pages it should involve, and many other factors. It’s a comprehensive document that includes the description of requirements divided into functional and nonfunctional.


Functional requirements involve:


  • User requirements describe what and how the app or software system should function from the user point of view: what users can make and what can’t, which activities they can perform and to which result each action will lead to.
  • Business requirements is the description of what the app must do from the business point of view. Think about objectives you want to accomplish and tasks your software solution must solve.
  • Functional requirements are the description of what and how the application should do. It includes the requirements to the product architecture, internal mechanisms, the interaction of different system components, database structure, and so on.
  • System requirements include the requirements for technological infrastructure, software supported versions, etc.   


Nonfunctional requirements include:


  • Requirements for attributes describe the requirements for product performance, scalability, and reliability.
  • Business requirements are determined by work internal regulations specific to the industry a customer’s company operates in and company needs as well.
  • Technical requirements include operating systems and platform limitations, programming languages, and other tech tools and technologies used in software development process.
  • Requirements to product/system appearance that involve design, brand book, design limitations, and more.
  • External interfaces are the requirements dictated by the necessity of integration with external information systems that don’t directly affect app functioning.
  • Limitations of external controllers include industry regulations, legislative acts, enactments, and licensing


Why is software requirements specification so important?

Unfortunately, about 70% software development projects underperform. This is a sad fact, happened because of various reasons. One of them is poor requirements for the product.

For example, lack of functional requirements in the spec, mismatch between time, budget, and the scope of work (f.e, when trying to implement multiple complicated features in one app for a short period of time), or cases when companies don’t write UX guidelines, set up unrealistic goals, and so on.
Here are several interesting facts representing the importance of creation software requirements document right:

  • 70% software development projects bring only marginal benefits or fail because of poor requirements.
  • Enterprises that don’t perform well the stage of requirements processing and SRS preparation, have much more chances of project failure.

On the other hand, a well-prepared software requirements document provides many essential benefits, highly increasing project success chances.


A detailed SRS enables:


  • Clearly understand how the app, website, or system must function, which tasks it must solve and how, how it will interact with users.
  • Clearly determine the time for mobile/web app development process, the budget required to build it, and scope of work.
  • Stick to the planned working schedule and project budget as well.
  • Make communication easy and convenient for both customer and software development team.
  • Ensure effective cooperation of app development team: all specialists have a clear vision of what needs to be done, how, and when.


Small tips of how to write software requirements document


  • Define project goals and value that your customers/users will get.
  • Think about how a software solution should look like. Find several examples of design you enjoy and some that you don’t like and think to be flawed.
  • Be specific – avoid of general notions such as “small”, “bright”, try to provide exact figures and requirements, up to color pixels if speaking about color.
  • Describe all the requirements in detail. If some of them are complicated and need technical expertise, include your technical specialists in the process of SRS preparation, or ask a software development company to write it.
  • Define a pricing model and app monetization strategy. If you have detailed requirements, your project doesn’t imply any changes (or maybe small only), you have a clear time and budget, it’s better to choose Fixed Price. If your project is supposed to have some changes in the requirements of software dev process, choose Time & Material model.
  • If you have some hesitations, ask your mobile/web app development company: skilled specialists will always help you and provide useful recommendations.

Thus, software requirements document is essential for any project. Certainly, for most people, it’s difficult to create a detailed technical specification that would include all the issues.

In such cases, it’s better to apply to a software development team with some requirements/project idea you have (features, business objectives, technology stack, etc.).

No doubt that SRS provides many advantages, highly improving cooperation of both sides, project management part, as well significantly increasing chances for project success.