What the document is for, and how long it should be
The document exists so that a team can estimate the work, build the right thing and prove it is finished. It is read by designers, engineers and testers, and later by whoever maintains the app. If a sentence does not help one of them, it does not belong.
Length follows the app. A booking app with one kind of user might need eight pages. A marketplace with customers, providers and an admin team needs more. Clear and short is better than complete and unread, and anything you are unsure about should go in a list of open questions instead of being left out.
The sections to include
| Section | The question it answers | Example line |
|---|---|---|
| Purpose and success | Why does this app exist, and how will we know it worked? | Patients book and change visits without phoning the clinic |
| Users and roles | Who uses it, and what may each role do? | Patient, receptionist, clinic manager |
| User tasks | What does each user need to get done? | As a patient, I can move my appointment to another free slot |
| Screens and flows | How do the tasks connect, screen to screen? | Sign in, home, choose clinic, choose slot, confirm |
| Data and integrations | What information is stored, and which systems are involved? | Appointments come from the practice system and are never stored only on the phone |
| Mobile conditions | How does the app behave on a real phone in real conditions? | Upcoming visits are readable with no connection |
| Quality requirements | How fast, secure and accessible must it be? | All text respects the text size the user has set on the phone |
| Release and stores | Which platforms, which stores, which regions? | iOS and Android, public stores, two countries |
| Out of scope | What are we deliberately not building now? | Payments and insurance claims are left for a later version |
Write requirements as tasks, each with a way to test it
The most useful habit is to write each requirement as something a user does, followed by the conditions under which you would accept it as done. These conditions are called acceptance criteria. They prevent many of the arguments that otherwise arrive at the end of a project.
One requirement, written three ways
A requirement for an invented clinic app, improved in two steps.
- VagueUsers can manage appointments.
- As a taskAs a patient, I can move an upcoming appointment to another free slot at the same clinic.
- With acceptance criteriaOnly free slots are offered. The old slot is released at once. The patient sees a confirmation and receives a notification. The change is not allowed once the cut-off set by the clinic has passed, and the app then shows the clinic phone number. The change appears in the practice system.
The third version can be estimated, designed, built and tested. It also exposes two decisions the business has to make, the cut-off rule and what happens after it.
Give each requirement a short identifier such as BK-04. Designs, test cases and later change requests can then point at it, and nothing is lost when wording changes.
The mobile details most documents miss
Documents written by people used to websites tend to describe screens and forget the phone. Each item below changes the design and the estimate, so decide it before you ask for a quote.
Mobile requirements checklist
0 of 10 checkedPrioritize with must, should and later
- 01
Mark every requirement
Must means the app cannot launch without it. Should means it matters and could follow shortly after. Later means it is recorded so that the design does not block it.
- 02
Test the musts against one question
Would we delay the launch for this? If the honest answer is no, it is a should.
- 03
Check the proportions
If nearly everything is a must, the prioritization has not been done yet.
- 04
Keep the later list visible
Engineers make better structural decisions when they know what is coming.
If this is a first version of a new product, planning a mobile app MVP shows how to cut the must list down to what proves the idea.
A requirements document template you can copy
Mobile app requirements document
Template1. Purpose and success
The problem this app solves, and for whom
How we will measure success after launch
2. Users and roles
Each role, what it can see and what it can do
3. User tasks
ID, task written as: As a role, I can do something
Priority: must, should or later
Acceptance criteria for each task
4. Screens and flows
The main flows, as a list of screens in order
Empty, loading and error states for each screen
5. Data and integrations
What is stored, where, and for how long
Each system the app talks to, and what passes between them
6. Mobile conditions
Offline behavior, notifications, permissions, devices and system versions
Sign-in methods and account recovery
7. Quality requirements
Performance, security, privacy and accessibility expectations
8. Release and stores
Platforms, stores, countries and languages
Who owns the store accounts
9. Out of scope
What this version will not include
10. Open questions
Decisions not yet made, and who will make them
Common mistakes
- Describing screens in detail and never saying what the user is trying to do
- Leaving out the admin side, which someone still has to build
- Writing like the competitor app as a requirement
- Listing only the path where everything goes right, with no errors, empty states or refusals
- Treating the document as finished, when it should change as you learn
- Mixing decisions with wishes, so that nobody knows which lines are agreed
What to do next
Fill in sections 1 to 3 of the template first. Those alone are enough for a useful first conversation with a development company, and how to choose a mobile app development company explains what to ask in it.
If you would like help turning notes into a document a team can build from, that is the purpose of a product discovery workshop. You can also send us what you have, and we will tell you what is missing before you ask anyone for a quote. Our mobile app development page describes how we take a document like this into design and build.
Common questions
What is the difference between a product requirements document and a software requirements specification?
A product requirements document says what the product should do for its users and why. A software requirements specification is more formal and adds detailed functional and quality requirements for engineers and testers. For most apps one document that starts with users and tasks and adds detail where risk is high does both jobs.
Do I need wireframes in the requirements document?
No. Rough sketches can help explain a flow, and they are welcome. Finished wireframes made before the requirements are agreed tend to lock in a layout too early. List the screens and what each must allow, and let the design phase produce the wireframes.
How detailed must the document be before I ask for a quote?
Detailed enough that two companies would describe the same app back to you. Roles, the must-have tasks, integrations and the mobile conditions are the minimum. Where you cannot decide yet, say so. A good company will price a discovery phase to settle the open points first.
Who should write the requirements document?
The person who owns the product, with the people who know the daily work, such as support, operations or sales. An engineer or a designer should review it for gaps. When nobody inside has the time, a discovery phase with an outside team produces the same document with you.
How do I handle requirements that change during the project?
Expect change and give it a route. Each change is written down against the requirement it affects, with its effect on cost and schedule, and someone with authority approves or declines it. The document is updated so that it always describes the app as agreed.
