Agile and waterfall are both frameworks for planning, executing, and delivering projects, including those in software development.
Agile and waterfall are two dominant methodologies for organising software development. This knowledge-base article outlines their origins, structure, advantages and disadvantages, and typical areas of application. Free from opinion or anecdote, it offers a factual comparison so readers can understand both approaches and make more informed choices.
Overview of agile vs waterfall
Agile and waterfall are both frameworks for planning, executing, and delivering projects, including those in software development. They mainly differ in how they handle scope, scheduling, change, and collaboration between stakeholders. This article describes the structure of both approaches, their key characteristics, and the contexts in which they are commonly used.
Key take-aways in this article:
Definition and origin of the waterfall method
Definition and characteristics of agile software development
Step-by-step comparison of both models across the software development life cycle
Overview of the advantages and limitations of each approach
Use cases where agile or waterfall is common practice
The waterfall model in software development
The waterfall model is a linear, sequential approach to software development. The project is divided into a fixed series of phases that are completed in a set order. Each phase is formally closed before the next begins, often with documentation and approval from the parties involved.
Typical phases in a waterfall process include problem or requirements analysis, functional and technical specifications, design, implementation, testing, acceptance and delivery, and maintenance. Organisations may use different labels in practice, but the defining feature remains that phases follow one another and returning to an earlier phase is limited or expensive.
In the traditional waterfall model, scope is fixed early, usually during the analysis and design phases. Planning and budget are determined on that basis. Changes during the project are often handled through formal change requests. This makes the method predictable in stable environments where requirements and regulations are largely known in advance and unlikely to change.
The waterfall model is widely used in sectors where processes are heavily regulated or where extensive documentation is required, such as certain industrial, financial, or government contexts. The emphasis is on documentation, formal decision-making, and traceability of the completed steps, so that it is clear afterwards which choices were made and on which specifications development was based.
Agile software development
Agile software development is an iterative and incremental approach focused on delivering working software step by step. Instead of one long linear trajectory, the work is divided into short iterations. At the end of each iteration there is a potentially deployable increment that can be reviewed by users and stakeholders.
Agile is not a single method but a collective term for several frameworks that share the same core principles. Examples include Scrum and Kanban. Typical characteristics are multidisciplinary teams with end-to-end responsibility and close collaboration with the client or product owner. Requirements are recorded in a product backlog and regularly prioritised based on value, risk, and feedback.
The ability to embrace change is central to agile. New insights, shifting market conditions, or user feedback can lead to a re-prioritisation of work. Scope is therefore treated as variable, while constraints such as time and budget are often set earlier. Documentation remains important, but the primary focus is on working software as the main measure of progress.
A key difference from the waterfall approach is that agile explicitly promotes continuous improvement. Teams regularly evaluate their way of working, for instance in retrospectives, and adjust processes based on real-world experience. This iterative nature makes agile attractive in domains where requirements are uncertain or volatile or where innovation and rapid feedback cycles are essential.
Comparing agile and waterfall in practice
Although agile and waterfall follow different philosophies, both aim to control the software development life cycle. It is therefore useful to compare the approaches phase by phase. In the initial phase, where the problem and objective are defined, waterfall emphasises capturing all requirements before development starts. Agile limits detailing to what is necessary to plan the first iterations, leaving finer details for later when more information is available.
During the design and implementation phases, waterfall typically relies on a comprehensive design document that underpins the entire build. Agile still applies architectural patterns and design principles, but development and design often run in parallel. Teams make frequent small design decisions based on current backlog priorities and feedback from earlier iterations. As a result, design and implementation are more intertwined in agile, whereas waterfall keeps them more clearly separated.
The testing process shows another clear difference. In the waterfall model, testing largely takes place after the implementation phase is completed. Testing is a separate phase, featuring activities such as system and acceptance testing. In agile processes, testing is usually integrated into every iteration. Developers and testers collaborate to apply test automation and quality assurance continuously, so findings are fed back quickly. This model is also common outside agile, for instance in continuous integration and continuous delivery.
In the delivery phase, the waterfall model often schedules one or a few large releases that deliver a complete system. Agile processes ship smaller releases more frequently, for example after each sprint or after several sprints, depending on the release strategy. For organisations this means the impact on training, documentation, and change management differs. Large releases require bigger one-off efforts, while frequent smaller releases demand continual adjustments to processes and user communication.
Risk management also highlights a contrast. The waterfall model tries to mitigate risks by creating clarity on scope and design up front and by running extensive test phases at the end. Agile approaches reduce risk by addressing uncertainty early, prioritising critical components in the first iterations, and collecting feedback continuously. Both approaches have their own style of risk management, tailored to the predictability of the product and its environment.
A video that visually explains the key differences between agile and waterfall methodologies can be found on YouTube: https://www.youtube.com/watch?v=iHup3LbiSXA. The video discusses practical examples of iterative and sequential project approaches and shows how method choices influence planning and execution.
What is the main difference between agile and waterfall?
The main difference lies in how the project is planned and executed. The waterfall method follows a linear process with consecutive phases, making change during the project relatively difficult. Agile works iteratively and incrementally, delivering working software in short cycles and making changing requirements part of the process.
When is the waterfall method suitable for software development?
The waterfall method is most suitable when requirements and regulations can be predicted in advance and are unlikely to change, for example in projects with strong compliance demands or a fixed contractual scope. In such situations the benefits of extensive documentation and clear phase transitions often outweigh the limited flexibility.
In which situations is agile usually applied?
Agile is typically used in environments with high uncertainty about the final product or the market, such as innovative digital products, online services, and applications that need regular adjustment based on user feedback. By working iteratively and dynamically prioritising the backlog, the team can respond more quickly to new insights and changing customer needs.
Can agile and waterfall be combined within one organisation?
Yes, it is possible to use both approaches side by side. Some organisations apply agile to product development and customer-facing initiatives, while still using the waterfall approach for infrastructure projects or projects with strict external regulations. In practice this creates a hybrid landscape in which governance and reporting must align with the different project types.
How do agile and waterfall affect the role of stakeholders?
In a waterfall project, stakeholders are mainly involved at the start, when defining and approving requirements, and again at the end during acceptance. In agile processes stakeholders are involved continuously, for example through reviews of iteration results and by prioritising the backlog. Agile therefore generally requires more ongoing interaction, whereas waterfall focuses on a few clear decision points.
Is agile inherently better than waterfall?
Neither approach is inherently better; suitability depends on context, risks, and requirements. In projects with high uncertainty and the need for frequent adjustments, agile offers clear advantages. In stable, heavily regulated environments, the predictability and documentation of waterfall may be more appropriate. The choice is therefore often based on product type, environment, and organisational preferences.
How does documentation differ between agile and waterfall?
In the waterfall approach, documentation plays a central role, with extensive specifications, design documents, and test reports produced for each phase. In agile, documentation is still important but is usually purpose-driven, for example as user stories, acceptance criteria, and technical documentation needed for maintenance. The emphasis shifts to documentation that remains current throughout the product’s life cycle.
