Importance of functional specification for your software development project

If you don’t know what the app should do, how will you know when it’s done?

If you describe only the approximate requirements to the development team, you can still get the final product that will formally meet them, but very likely it won’t be the one you expected to get. Without understanding how features should function, the development team can implement them by their judgment, which can result in confusion.

Having a good technical specification increases the chances of a successful software development project, service, or feature that all stakeholders will be happy with. This reduces the likelihood that something will go wrong during implementation and even after you’ve launched your product.

Either you are outsourcing software development or manage your in-house team, you need specifications to get what you want (or at least nearly what you want). 

What is a Software Specification?

Software specification is a set of documents, primarily technical and functional specifications, which describe software development project goals, functionality, details required for a development team.

Software specification describes how the software product will be used from a user perspective and its performance details such as speed, availability, and response time. You can create a software specification for any tech project, be it complicated software, apps, or websites.

Its main purpose is to make smooth communication with project managers, designers, QA engineers, software developers, and other team members successful and explain what everyone needs to do.

Do not confuse technical and functional specification

Some people consider both functional and technical specifications as “technical”, but the functional one is about what a user will deal with while the technical one is a description of what a developer should implement. Let’s deep dive into a little more detail.

Who usually writes it

Who uses it

Main purposes
Functional specificationNon-technical person: product owner, project or product manager, business analyst.
All project stakeholders.

describes how the product will perform.
– describe in detail for software developers a product’s intended capabilities, appearance, and interactions with users.
– capture the intended behavior of the system.
– They help define things such as system calculations, data manipulation and processing, user interface and interaction with the application.
– support business processes and requires an understanding of things such as accounting, plant maintenance, sales, etc.
Technical specificationTechnical person: an engineer who will build the solution; for big projects — technical leads, project leads, or senior engineers.Primarily engineers. – describes the technical aspects of product software development.
– outlines how your team is going to address a technical problem by designing and building a solution for it.
Source: Beeminder.

Why is Technical Specification important for your software development project?

1. Better idea presentation. A specification will help you communicate your idea to a development team more effectively and at the same time, will help you understand it even better yourself. Functional and technical specifications work as unified documents for the common understanding of the project across different team members.

2. A team is on the same page. All team members could use the documentation as a reference to fully understand their project. There are a few different approaches to the development of the same feature. And there must be the same vision in the minds of everyone in the team to deliver a perfect end-product. 

Besides software developers, with specifications the Project Manager will be able to easily plan the work, and create features that can be implemented out of documentation; Quality Assurance engineers will be able to provide high-quality testing results following the documentation.

3. Better task distributions, the team will feel confident as they know what needs to be done because the technical specification was agreed by required parties.

4. It helps to prioritize to make sure which are the most impactful and urgent parts of a project.

5. Hidden project mechanics. The project may have a lot of hidden details that can’t be seen on the surface. To discover them, you need to talk about them in detail and examine everything closely. When all is said and done, those hidden mechanics are revealed. Documenting your work throughout the process ensures that people won’t forget about these details along the way.

When writing a technical specification, engineers have to break down the work they’ll have to do during implementation to ensure that no part of it is overlooked.

6. Technical specification improves your project’s estimations

It’s almost impossible to estimate the project requirement if the product specifications are not in place. This means that too much time, money, and effort can be wasted on a project before it is even taken into consideration. And this often leads to a failure during the distribution of workload.

Writing functional specifications for software packages keeps a company from having unexpected budget increases. When features are documented and the budget is clear, it’s easy to control the whole process.

The best-planned specs serve as a great guide for measuring success and return on investment of engineering time.

7. Proper scheduling and saving time. A carefully crafted project functional specification helps to assess the workload of the whole team and each member separately, which prevents them from feeling overloaded. Additionally, it precisely assigns tasks and checks progress for software product development. 

New teammates that are unfamiliar with the project can get themselves integrated into the project implementation as soon as possible.

Not having a clear idea of the development process, there is a high risk that it may not go smoothly. This problem is compounded when people have to be involved in all aspects of the project. Altogether this can lead to a budget blowout and unclear objectives.

8. Scalability. Software development team members will never know how scalable your project should be until you tell them and, of course, document it. You may prefer to keep some mechanics a secret; however, for project scalability, it’s better to inform your dev team about your growth plans in advance. 

For instance, if you plan to launch your project in Germany, don’t forget to add “for now.” It may seem easy to add a language without any consequences. However, for some projects, the architecture needs to be significantly restructured or even completely rebuilt from scratch, making them more complex and time-consuming.

Despite this, if a project is really big, it takes years to build. Thus, you may need to know how that particular feature worked a few years ago.

9. Contractor change. It is not an obvious problem when you make a deal with a software development company, but let’s imagine for some reason you decide to switch to another contractor. Having a well-documented functional specification will make it easier for you to not have to explain everything from the beginning. 

10. More efficient and transparent work. First of all, technical specification saves you from repeatedly explaining your vision to multiple team members and stakeholders. A software project based on a specification can offer seamless workflow, rational and clear communication to all parties involved. By creating a spec document you reduce the chaos that may build up during the project. Everyone involved knows exactly what to do, as well as when and how to do it.

Since the team is aligned and in agreement on what needs to be done through the technical specification, big projects can progress faster. 

11. Meeting your expectations. The team must be 100% clear on how the project functions to provide you with the end product that meets your expectations.

When you do not need a software specification

Two decades ago, software developer and Trello creator Joel Spolsky wrote that any project which required over a week of coding work would suffer without a fully defined spec. And we agree with him. 

You don’t need a specification for every project, so make this judgment based on the timeline and budget you have.

How to Get a Specification for Your Project? 

1. Your product manager, project manager or business analyst write a functional specification and a software engineer prepares technical specification.

2. You take your time and create a functional specification yourself. Here you will find some tips. To prepare a technical specification you need to consult with technical specialists

For functional specs, if you aim to create them yourself, put in as many details as possible. Use the approach of ‘zero-knowledge’ — assume that the reader knows nothing, describe all the details, no matter how obvious it seems. And don’t be afraid to repeat yourself. If you forget something, it’s going to cause a mess. 

3. You get a quality document after a detailed discovery phase with professionals. You provide a software development company with basic information about your product. After reviewing the final document and confirming it with the provider, you can then go into software development with freelancers, your in-house team, or with a software development agency.
4. Writing technical and functional specifications as a part of the discovery phase and software development.


It’s better to spend some time documenting the project functionality before beginning development rather than get possible issues during development and in production. All this will make a negative impact on your time, budget, and energy. Custom software development requires clear objective-setting and thorough documentation to meet the goals and expectations of customers to a tee.

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