The article was updated on March 16, 2021.

The key to a successful application is determined right from the start. Apart from understanding what you want, you need to know how to get the message across to your development team. If the mobile app specification is unclear and fuzzy then your development team will certainly come across some roadblocks during the development process.

In this article, we will share our expertise in creating a mobile application specification template that will begin the first stage of app development and turn the long development journey into an enjoyable and streamlined process. Read on to learn more!

What is functional specification?

First of all, a functional specification is a document that lists all the requirements and the first set of features to implement for a product you will be developing. A mobile app specification document translates stakeholders’ vision into concrete guidelines for developers and helps them calculate the product development cost.

So what should a functional specification contain to meet these objectives? Normally, a mobile app spec provides a detailed vision of core product development aspects:

Product overview –  its audience, use cases, and the examples of ‘pains’ it will help users resolve.

Product risks –  including steps the support team should be taken in case of disruptions and errors. The steps for product testing also fall into this category.

Product’s requirements – both functional and non-functional, including the order for their implementation.

Finally, a mobile app specification contains development deadlines and budgets.

Why do you need a functional specification?

An app specification has another important purpose – it aggregates conflicting stakeholders’ requirements into a well-rounded outline. The benefits are quite tangible:

• avoiding confusion,
• reducing the number of iterations,
• accelerating product development, and
• helping estimate the development costs.

Ultimately, creating a functional specification for a product begins with an initial development phase and may determine the failure or success of your mobile app.

How to write a functional specification for a mobile app

So how do you approach writing a functional specification document for a mobile app? Rarely does the task of developing this document fall on the shoulders of just one person. Normally, a project manager teams up with UI/UX designers, developers, and product stakeholders to brainstorm and create a clear vision for the product and its features.

Based on our expertise and experience, here’s our outlook on how to write a functional software specification.

1. Introduction to a mobile application specification

To begin, briefly describe the purpose of the mobile app requirements document and specify the person who is responsible for updating the specs.

You should then provide general information about the product. Specify the app’s goal, its’ target audience and the platforms that it is supposed to run on. Mention similar products that have been completed by your competitors. List the desired technologies that you wish to use for the creation of your application.

And finally, specify the terms that you are going to use throughout the mobile app requirements document, as shown in the example below.

2. Main User Stories

List all the different types of users who are going to use your application. Some applications have only one role, while others have two or more of them. Describe the user stories for each role. This will help both you and your developers better understand the required functionality from a user’s point of view.

As an example, let’s consider an app that has only 2 roles – an administrator and a regular user. In this case, the user stories will look like as follows.

As a user…

• [US01] I want to sign in/up either by email and password or by Facebook.
• [US02] I want to be able to make orders quickly.
• [US03] I want to get a notification when my order has been delivered.

As an administrator…

• [US04] I want to be able to see and manage the list of users.
• [US05] I want to be able to see real time statistics on the orders which have been delivered.

Describe which screen should be accessed by each role. See an example below.

3. Main Screens

In this section of the mobile app development requirements document you need to describe each and every screen of your mobile app.

Start with a wireframe or a ready design and then describe all the details of the screen:

• Which fields are mandatory in the form;
• What are the default positions of the switchers;
• What will happen when the specific button or link is clicked, etc.

Make sure to represent the data in a convenient way for your readers. Use tables when and where appropriate.

Every screen is important. As a reminder, don’t forget about the screens that your administrator has access to.

4. High-level design

• Define the technology stack that will be used, including the backend, the frontend as well as mobile technologies.
• Create the database schema. It may seem to not be important at this stage. but, the fact is, that it is one of the most efficient ways to understand all the components of the system. Define the tables and their relationships, and make sure that the data supports the processes that were defined in the app specification.
• Decide on the the data structures. You need to decide what data should be saved (if any), and what will be lost when users close the application. Also, specify where the data should be stored, whether that is going to be on the user’s device, cloud or a server.
• Specify all the languages and script writing systems (e.g., RTL) to be supported by your mobile application.
• You also need to define the required third party integrations, decide on how to deal with performance and security issues and describe the supporting infrastructure of the application.

After specifying all the information mentioned above, feel free to write any other comments, concerns, questions or special requests related to the project such as ways to communicate.

Questions to help you write a good functional specification

To write a high-quality functional specification, you need to cover a wide scope of app development facets.

Below is a list of questions to ask yourself to create clear mobile app specification guidelines.

1. What are your app’s business objectives? Think about the purpose of your app, its business idea, and the problems that it will help users resolve.
2. Is it an update of an existing product, or will you be building an entirely new app from the ground up?
3. Who are its end users? The more you know about their age, income, and background, the better.
4. List the platforms (iOS, Android), including versions, that your end product will run on.
5. List the devices (smartphones, tablets) that your app will run on. Will you include a desktop version for your mobile app?
6. Define your app functions, i.e. what exactly will it enable users to do?
7. Define your app features. Login, payment processing, push notifications, and alerts are examples of features that your mobile app may or may not have.
8. Will your app integrate with third-party platforms and services? For example, a fintech app may integrate with platforms for payment processing, such as Zelle.
9. Will your app include analytic modules? In other words, will it collect and process data for user behavior analytics and other insights?
10. What materials will developers need to complete the project? Design, copywriting, documentation, and other materials may fall into this category.
11. Will your app be uploaded to GooglePlay/AppStore, or self-published? Self-publishing may have a number of benefits, such as the ability to work at your own pace and set your own deadlines.
12. What tasks will the developers have to complete? The tasks may include coding, testings, UI design, and product support services.
13. Which tasks fall beyond the scope of the development team? For example, server configuration for the mobile app backend may not be included in the list of tasks for your development team. 

After you’ve covered all these facets of the app development process, you should be capable of setting up the project timeline and budget – which should also be included in your mobile app specification.

Summing up

Properly developed and detailed app specification enables software development companies to provide an accurate time and cost estimation for the entire project. However, as you can see, proper mobile application specification lays the groundwork for the future of the product. It requires deep expertise in technology and has to be created by an experienced product manager.

That’s why we advise our clients to start a collaboration process with a software development company and define the proper product requirements.

Ready to discuss your product? Contact us to schedule a kick off meeting to discuss how our team can help you translate your business idea into a professional mobile application specification.