Summarize this article with:
Most software projects don’t fail because of bad code. They fail because the team tried to build everything at once.
Incremental software development fixes that by splitting a project into smaller, functional pieces. Each piece gets built, tested, and delivered on its own before the next one starts. NASA used this approach in the 1960s. Agile teams use it today.
So what is incremental software development, and why does it keep showing up across every major development methodology?
This article covers how the incremental model works, its phases, the different types, when to use it, and when to pick something else. You’ll also see how it compares to iterative development, the Waterfall Model, and the Spiral Model.
What is Incremental Software Development
Incremental software development is a software development process that breaks a project into smaller functional parts called increments. Each increment goes through its own cycle of planning, design, coding, and testing before delivery.
The full system isn’t built all at once. Instead, the team delivers a working version of the software after each cycle, adding new features progressively until the product is complete.
This approach sits within the broader software development lifecycle as one of several recognized development methodologies. It shares DNA with Agile, Scrum, and the Spiral Model, but it predates most of them.
NASA used incremental development on Project Mercury back in the 1960s. IBM engineers later applied it to the Space Shuttle’s primary avionics software between 1977 and 1980, running 17 iterations over 31 months.
The U.S. Department of Defense formalized incremental practices through DOD-STD-2167 in 1985, and later through MIL-STD-498.
So this isn’t a new idea. It’s a proven project management approach that splits complex systems into manageable pieces, each one functional enough to test and use on its own.
How Does the Incremental Model Work
The incremental model works by dividing the entire software system into modules. Each module represents a self-contained chunk of functionality that the team builds, tests, and delivers independently.
Here’s what a single increment cycle looks like:
- Requirement analysis for that specific increment
- System and module design
- Code implementation
- Testing and validation of the new build
- Integration with previously completed increments
- Delivery and stakeholder review
The first increment usually covers the core functionality. Think of it as the minimum viable version. A mobile banking app might ship account creation and balance checking first, then add transaction history and bill payments in later increments.
After each delivery, the team collects user feedback. That feedback directly shapes what goes into the next cycle.
The whole thing repeats until every planned feature is built and integrated into the final product. Each cycle follows the same structured steps, but the scope narrows to just the features assigned to that particular increment.
One thing that trips people up: the codebase grows with every cycle. That means regression testing becomes more important as you go. You can’t just test the new stuff. You have to confirm the old stuff still works too.
What Are the Phases of Incremental Development
Every increment passes through the same set of phases. The structure mirrors a traditional waterfall cycle, but it runs on a smaller scale and repeats multiple times across the project.
How Does Requirement Analysis Work in Incremental Development
The team defines functional and non-functional requirements for the current increment. High-level requirements for the full system are captured early through requirements engineering, but each cycle only addresses a specific subset.
How Is System Design Handled Per Increment
The software architect plans the module’s structure so it fits cleanly into the existing system. A solid design document at this stage prevents integration headaches later.
What Happens During Increment Implementation
Developers write and build the code for that increment’s features. The code review process runs alongside implementation to catch issues early.
How Is Testing Done Within Each Increment
Unit testing covers individual components. Integration testing confirms the new increment works with everything built before it. The software testing lifecycle runs in full for each cycle, not just at the end of the project.
What Does Deployment Look Like for Each Increment
Each completed increment goes through app deployment and lands in a production environment or staging area. Teams using a build pipeline can automate most of this.
How Does Feedback Collection Fit Into the Process
Stakeholders and users review the delivered increment. Their input feeds directly into the planning for the next cycle. This feedback loop is what separates incremental development from rigid sequential models.
What Is the Difference Between Incremental and Iterative Development
These two terms get used interchangeably. They shouldn’t be.
Incremental development adds new functionality with each cycle. You’re building new pieces and attaching them to the existing system.
Iterative software development revisits and refines existing functionality. You’re reworking what’s already there based on feedback or new understanding.
Here’s a quick comparison:
- Incremental: each cycle delivers a new feature or module
- Iterative: each cycle improves an existing feature or module
- Incremental focuses on scope expansion
- Iterative focuses on quality refinement
In practice, most modern teams combine both. Scrum sprints, for instance, deliver new features (incremental) while also refining earlier work based on user feedback (iterative).
The DOD-STD-2167 standard from 1985 already acknowledged this overlap. It described scenarios where multiple development cycles could run at the same time, mixing both approaches within a single project.
Craig Larman and Victor Basili traced the history of combined iterative and incremental development back to Project Mercury at NASA. The pattern has been around for over 60 years.
What Is the Difference Between Incremental and Waterfall Models
The Waterfall Model runs every phase once, in sequence, for the entire system. Requirements first, then design, then implementation, then testing, then deployment. No going back.
The incremental model runs those same phases multiple times, once per increment. Each cycle produces a working version of the software.
Key differences:
- Delivery timing: Waterfall delivers the complete product at the end. Incremental delivers working parts throughout the project.
- Feedback: Waterfall collects feedback after the full build. Incremental collects it after every cycle.
- Risk: Waterfall concentrates risk at the end (you find out late if something is wrong). Incremental spreads risk across every increment through early defect tracking.
- Flexibility: Waterfall locks requirements upfront. Incremental allows change request management between cycles.
- Testing: Waterfall tests at the end. Incremental runs multiple types of software testing per increment.
Waterfall still works for projects where requirements are fixed and well-understood from day one. Think compliance-driven systems or projects with strict software requirement specifications that won’t change.
But for anything where requirements shift, where users need to see progress early, or where the system is too large to build all at once, the incremental model is the better fit. Most software development lifecycle models used today borrow from incremental principles for exactly that reason.
What Are the Types of Incremental Development Models
Not all incremental approaches look the same. The core idea stays consistent (build in parts, deliver in parts), but the execution varies depending on team size, risk tolerance, and project complexity.
Four main types show up across the industry.
What Is the Staged Delivery Model
The staged delivery model plans every increment upfront in a fixed sequence. Each stage delivers a functional slice of the system, and the order is locked before development starts. Best suited for projects with stable, well-understood requirements.
What Is the Parallel Development Model
Multiple teams build different increments at the same time. Each team handles its own module independently, and everything gets integrated at defined checkpoints. Faster overall delivery, but coordination overhead goes up significantly, especially around source control management and dependency tracking.
How Does Agile Use Incremental Development
Agile frameworks like Scrum and Extreme Programming treat sprints as increments. The Agile Manifesto (2001) built its philosophy around delivering working software frequently, which is incremental development at its core. Sprints typically run two to four weeks, each producing a shippable product increment.
What Is the Incremental Commitment Spiral Model
Barry Boehm’s ICSM combines incremental delivery with built-in risk assessment at every stage. Each increment includes a risk analysis step before the team commits resources to the next cycle. Designed for complex, high-risk systems engineering projects where uncertainty is high and stakes are serious.
What Are the Advantages of Incremental Software Development
The benefits are practical, not theoretical.
- Early delivery of working software. Users get something functional fast, not after months of waiting.
- Reduced risk through phased testing. Bugs surface early when they’re cheaper to fix, supported by strong software quality assurance practices.
- Easier requirement changes. Adjustments between increments don’t blow up the whole project.
- Faster user feedback. Real users interact with real software after every cycle.
- Lower initial cost. The team builds and funds the most critical features first.
- Manageable complexity. Smaller modules are easier to design, build, and debug than a monolithic system.
Teams working on mobile application development or web apps see these advantages clearly. Ship a core feature set, measure how people use it, then build the next piece based on actual data.
What Are the Disadvantages of Incremental Software Development
It’s not perfect. Some real problems come with this approach.
- Dependency management between increments gets tricky. If increment three relies on something from increment five, you have a scheduling problem.
- Scope creep. Constant feedback tempts teams to keep adding features beyond the original plan.
- Architecture risk. Poor design decisions in early increments can haunt the entire project. A weak foundation doesn’t support 15 modules stacked on top of it.
- Higher coordination effort. Multiple cycles mean more planning meetings, more integration checkpoints, more communication overhead.
- Total cost can climb if planning is loose. Each cycle adds its own overhead for testing, deployment, and review.
Teams without experience in configuration management and version control often struggle the most. The incremental model demands discipline around source control from day one.
When Should You Use the Incremental Model
Certain project conditions make incremental development the obvious choice:
- Requirements are unclear or expected to change during the project
- The development timeline is long (six months or more)
- Stakeholders need to see working progress early
- The system is large and complex enough that building it all at once is risky
- The team needs early market entry, even with limited features
- A feasibility study has flagged technical unknowns that need real-world testing
Think e-commerce platforms, healthcare software, fintech products. Any project where user feedback directly shapes what gets built next.
Successful startups often default to incremental delivery because they can’t afford to build everything before validating the idea.
When Should You Not Use the Incremental Model
It’s the wrong choice when:
- The project is small with fixed, fully documented requirements
- Regulatory standards require complete system software validation before any deployment
- The development team lacks experience managing multi-cycle integration
- Software compliance rules demand that the full system pass verification as a single unit
Some safety-critical systems in aerospace or medical devices can’t ship partial functionality. The incremental model adds unnecessary overhead in those cases. A sequential approach with a locked software development plan works better there.
How Does Incremental Development Handle Testing
Testing runs during every single increment, not at the end of the project. Each cycle has its own dedicated testing phase that covers the new features and everything built before them.
A typical testing flow per increment:
- Unit tests validate individual components
- Integration tests confirm the new module connects properly with existing ones
- Regression tests check that older features still work after the new code is added
- System tests evaluate the complete product as it stands after that increment
Many teams pair incremental development with test-driven development, writing tests before writing the actual code. Behavior-driven development also fits well here, since each increment has clearly defined acceptance criteria tied to user-facing behavior.
Automated testing through a continuous integration setup is almost a requirement. Manual testing alone can’t keep up when the codebase grows with every cycle.
What Are Real-World Examples of Incremental Software Development
NASA’s Project Mercury (1960s) is one of the earliest documented uses. Engineers built the flight software in small functional pieces, testing each one before integration.
The Space Shuttle primary avionics software system (1977 to 1980) used 17 increments over 31 months, averaging about eight weeks per cycle. The team at IBM chose this approach specifically because shuttle requirements kept changing during development.
Modern examples are everywhere. A fintech company launching a mobile banking app might ship account creation first, then add payment features, then investment tools, each as a separate increment with its own software release cycle.
E-commerce platforms do the same thing. Product catalog and checkout go first. Wishlists, advanced search filters, and recommendation engines come in later increments based on user data.
SpaceX and Rocket Lab both apply incremental principles to their launch vehicle software, running frequent updates and testing cycles between missions.
How Does Incremental Development Compare to the Spiral Model
Barry Boehm introduced the Spiral Model in 1986. It shares the incremental structure of building in cycles, but adds a formal risk assessment step to every loop.
Each spiral loop includes four sectors: objective setting, risk analysis, development, and planning for the next loop. The incremental model doesn’t require a risk analysis phase by default.
Key differences:
- The Spiral Model is risk-driven. The incremental model is feature-driven.
- Spiral works best for large, high-uncertainty projects. Incremental works across a wider range of project sizes.
- Spiral requires more upfront effort in risk evaluation. Incremental focuses that effort on software modeling and feature prioritization.
Boehm’s later work, the Incremental Commitment Spiral Model (ICSM), merges both approaches. It applies incremental delivery with concurrent risk management, designed for complex systems engineering projects.
What Role Does Customer Feedback Play in Incremental Development
Modern project management platforms support incremental development workflows. Teams can plan, track, and adjust increments based on actual progress.
Kanban boards visualize work in progress and identify bottlenecks before they impact delivery schedules.
Sprint planning tools help size increments appropriately and track completion against original estimates.
Version Control and Code Management Systems
| System | Primary Function | Hosting Model | Key Differentiator |
|---|---|---|---|
| Git | Distributed version control system for tracking code changes and project history | Local repositories with decentralized architecture | Command-line foundation for all modern version control workflows |
| GitHub | Cloud-based Git repository hosting with collaborative development tools | Microsoft-owned SaaS platform with freemium pricing model | Largest developer community and open-source ecosystem integration |
| GitLab | Comprehensive DevOps platform with integrated CI/CD and project management | Self-hosted or cloud-based with enterprise-focused solutions | Complete DevOps lifecycle management in single application |
| Bitbucket | Git repository management with Atlassian ecosystem integration | Atlassian-owned cloud service with enterprise team focus | Native integration with Jira, Confluence, and Atlassian toolchain |
| Mercurial | Distributed version control system emphasizing simplicity and performance | Cross-platform tool with Python-based architecture | Simplified branching model and consistent command interface |
Feedback is the mechanism that makes incremental development adaptive instead of just sequential.
After each increment ships, users interact with the working software. Their input, what works, what’s confusing, what’s missing, goes directly into planning the next cycle.
This feedback loop does a few concrete things:
- Reduces the risk of building features nobody wants
- Catches usability problems early when UI/UX design fixes are still cheap
- Gives product owners real data for prioritizing the backlog
- Keeps the project aligned with actual user behavior, not assumptions
Without this loop, the incremental model is just a waterfall split into smaller waterfalls. The feedback is what makes it work.
Failed startups often share a common trait: they built the whole product before asking users what they actually needed. Incremental delivery with real feedback prevents that.
How Do You Plan Increments in a Software Project
Planning happens at two levels: the full project scope and the individual increment scope.
At the project level, the team defines the complete feature set through a requirement specification and builds a risk assessment matrix to identify which features carry the most uncertainty.
From there, features get assigned to increments based on:
- Business value (highest-value features ship first)
- Technical dependencies (build the foundation before the walls)
- Risk level (tackle unknowns early while there’s still room to adjust)
- Stakeholder priorities
Each increment gets its own timeline, resource allocation, and software test plan. The development roles and responsibilities are defined per cycle so everyone knows what they own.
Version control and software configuration management are non-negotiable here. Without them, parallel work across increments turns into chaos fast. Proper technical documentation at every stage keeps the project traceable and auditable as increments pile up.
A solid project management framework ties all of this together, giving the team a repeatable structure that scales across five increments or fifty.
FAQ on What Is Incremental Software Development
What is the incremental model in software engineering?
The incremental model is a development methodology that builds software in small, functional parts called increments. Each increment goes through requirement analysis, design, coding, and testing before delivery. The system grows with each completed cycle.
What is the difference between incremental and Agile development?
Agile is a broader philosophy that includes incremental delivery as one of its core practices. Scrum sprints are increments. Incremental development is the delivery structure, while Agile adds values like collaboration, adaptability, and continuous improvement on top of it.
What are the main phases of incremental development?
Each increment passes through five phases: requirement gathering, system design, implementation, testing, and deployment. These phases repeat for every increment until the full software system is complete and all planned features are integrated.
When should you use the incremental model?
Use it when requirements are unclear, the project timeline is long, or stakeholders need early working software. It fits well for large, complex systems where building everything at once carries too much risk.
What are the advantages of incremental software development?
Early delivery of working software, faster user feedback, lower initial cost, and easier requirement changes between cycles. Bugs get caught early through phased testing, reducing the cost of fixes later in the project.
What are the disadvantages of the incremental model?
Dependency management between increments gets complicated. Scope creep is a constant risk. Poor architecture decisions in early increments can damage the entire project. Teams also face higher coordination overhead across multiple development cycles.
How is incremental development different from the Waterfall Model?
Waterfall delivers the complete product at the end after a single pass through all phases. The incremental model delivers working parts throughout the project, collecting feedback and adjusting between each cycle.
Can incremental and iterative approaches be combined?
Yes. Most modern teams combine both. Incremental adds new features per cycle. Iterative refines existing ones. Scrum naturally blends both approaches within sprint-based delivery, and the practice dates back to NASA’s Project Mercury in the 1960s.
What is the role of testing in incremental development?
Testing runs during every increment, not just at the end. Each cycle includes unit tests, integration tests, and regression tests. This catches defects early and confirms that new code works with everything built before it.
What is the Incremental Commitment Spiral Model?
Barry Boehm’s ICSM combines incremental delivery with formal risk assessment at every stage. The team evaluates risks before committing resources to the next increment. It’s built for complex, high-uncertainty systems engineering projects.
Conclusion
Incremental software development isn’t a trend. It’s a structured approach to building software that has worked since the 1960s, from NASA’s flight systems to modern feature-driven development teams shipping products every two weeks.
The model works because it breaks complexity into manageable cycles. Each cycle produces working software, collects real feedback, and feeds that data into the next build.
It won’t fit every project. Fixed-scope systems with strict audit requirements or teams without solid change management practices will struggle with it.
But for teams building complex systems where requirements shift and users need early access, incremental delivery reduces risk, cuts waste, and keeps the project grounded in actual user needs instead of assumptions.
Pick the right model for your project. Sometimes that’s incremental. Sometimes it’s not. The important part is making that choice based on your constraints, not habit.
Many of his resources are available on various design marketplaces and for free on Codepen.
Over the years, he's worked with a range of clients and contributed to design publications like Design Your Way, Designmodo, WebDesignerDepot, WPDean, and Speckyboy, and Slider Revolution among others.
- What Is Screen Time on iPhone - April 17, 2026
- How to Choose the Right B2B Contact Data Tool for Your Sales Team - April 17, 2026
- Android App Drawer vs Home Screen: Differences Explained - April 16, 2026
