How does Agile differ from Waterfall?

Agile and Waterfall (cascade model) are two opposite approaches to organizing software development. The main difference between them is flexibility and the way a project moves through its stages.

#1. Sequence of stages

Waterfall: All stages proceed strictly one after another: analysis → design → development → testing → implementation. Each step must be completed before the next one begins. Going back is almost impossible: if an error is found at a late stage, fixing it is expensive and slow.

Agile: The project is split into short iterations (sprints), each of which includes all stages at once, from analysis to testing. After each iteration the team gets feedback and can change direction. The process is flexible and cyclical.

#2. Change and adaptability

Waterfall: Requirements are fixed in advance. Any changes after the specification is approved are considered a risk - they break the timeline and budget. Suits stable projects where everything is known in advance.

Agile: Change is part of the process. The team expects requirements to change, and the project is built so that this is easy. The priority is fast adaptation, not strict adherence to a plan.

#3. Interaction with the client

Waterfall: The client takes part at the start (formulates requirements) and at the end (accepts the result). The whole process between these points is a "black box" for them. If the outcome does not match expectations, the project has to be redone.

Agile: The client is actively involved throughout the project. After each sprint they see the result, give feedback, and help adjust priorities. The risk of misunderstanding drops close to zero.

#4. Documentation and control

Waterfall: Strong emphasis on documentation and formal reports. Detailed plans, specifications, and diagrams are created before development starts. The priority is following the plan.

Agile: Documentation is minimal and only supports the work. The main control tool is daily communication, demos, and sprint results.

#5. Goal and philosophy

Waterfall: build the product according to the plan. Agile: build the product that the user needs right now.

#In short

Summary: Waterfall is a rigid plan, Agile is constant movement and adaptation. If Waterfall is like building a bridge from a blueprint, then Agile is like navigating the sea, where the course is adjusted depending on the wind and waves.