Cybersecurity glossary
What is Software Development Lifecycle (SDLC)?
Learn what the Software Development Lifecycle is, how SDLC organizes software delivery, and how it differs from SSDLC and DevSecOps security practices.
Definition
The Software Development Lifecycle (SDLC) is the structured process teams use to plan, design, build, test, release, operate, and maintain software.
Why SDLC matters
Software delivery involves many decisions that can drift apart: what to build, how to design it, who reviews it, when it is tested, what qualifies for release, and how defects are handled afterward. Without a shared lifecycle, teams rely on memory and individual habits.
The Software Development Lifecycle (SDLC) gives delivery work a map. It creates predictable phases, handoffs, feedback loops, and quality expectations so software can move from concept to operation with less chaos.
What an SDLC organizes
Product intent
Planning and requirements clarify the user problem, constraints, success criteria, and delivery scope.
Technical design
Architecture, interfaces, data models, and implementation choices are made visible before or during build.
Quality feedback
Reviews, tests, builds, and acceptance checks provide evidence that changes are ready to ship.
Operational learning
Support, monitoring, incidents, and maintenance feed lessons into future planning.
A common SDLC flow
Plan and prioritize
Define goals, users, constraints, responsibilities, and the value the software should deliver.
Specify requirements
Capture functional needs, nonfunctional expectations, dependencies, acceptance criteria, and constraints.
Design the solution
Choose architecture, interfaces, data structures, user experience, and integration patterns.
Implement and review
Write code, review changes, run builds, and keep work aligned with standards and ownership.
Test and release
Validate behavior, fix defects, prepare deployment, and decide whether the release criteria are met.
Operate and maintain
Monitor reliability, handle bugs, update dependencies, respond to incidents, and improve the next cycle.
SDLC versus SSDLC
| Area | SDLC | SSDLC |
|---|---|---|
| Goal | Deliver useful software through a managed process | Deliver useful software with built-in security assurance |
| Requirements | Functional and nonfunctional product needs | Security, privacy, abuse, compliance, and assurance requirements |
| Testing | Quality, regression, performance, and acceptance testing | SAST, SCA, DAST, IAST, threat validation, and secure configuration checks |
| Operations | Maintenance, support, reliability, and defect handling | Vulnerability response, incident learning, security monitoring, and risk exceptions |
SDLC checklist
- Define lifecycle phases and decision points in language teams actually use.
- Make ownership clear for requirements, design, code review, testing, release, and maintenance.
- Use acceptance criteria so teams know what finished means before implementation starts.
- Automate builds, tests, and deployments where repeatability matters.
- Keep traceability between requirements, changes, release artifacts, and post-release issues.
- Add security activities explicitly if the base SDLC does not already require them.
- Review bottlenecks and escaped defects to improve the lifecycle instead of blaming one phase.
- Adapt the model to product risk, release cadence, regulatory pressure, and team maturity.
The practical takeaway
SDLC is the delivery framework: it explains how software work moves from idea to operation. It is valuable because it makes expectations, evidence, and feedback loops visible.
Security is not guaranteed by SDLC alone. Use SSDLC practices when the lifecycle must explicitly manage secure design, component risk, security testing, and vulnerability response.
Related security terms
Secure Software Development Lifecycle (SSDLC)
The security-enhanced lifecycle that extends SDLC with assurance activities and controls.
CI/CD Pipeline
Automation that moves SDLC changes through build, test, and deployment stages.
Code Review
A quality and security practice commonly used during the implementation phase.
Shift Left Security
An approach that moves security feedback earlier in the SDLC.
Static Application Security Testing (SAST)
A code-analysis practice that can run during SDLC implementation and build phases.
Frequently asked questions
What is SDLC in simple terms?
SDLC is the repeatable process a team follows to turn an idea into working software and then maintain it after release.
What are common SDLC phases?
Common phases include planning, requirements, design, implementation, testing, release, operations, and maintenance. Agile teams may repeat these phases in small cycles.
How is SDLC different from SSDLC?
SDLC organizes software delivery in general. SSDLC adds explicit security requirements, threat modeling, secure coding, security testing, supply-chain controls, and vulnerability response.
Is DevSecOps the same as SDLC?
No. DevSecOps is an operating approach that integrates security into development and operations. It can be applied within many SDLC models.
Does every organization use the same SDLC?
No. Teams adapt lifecycle models such as waterfall, agile, spiral, or continuous delivery based on product risk, regulation, team size, and release cadence.
Where does security belong in SDLC?
Security belongs in every phase, but the general SDLC does not guarantee it. That is why teams define SSDLC practices and evidence.
Why document the SDLC?
Documenting the lifecycle clarifies ownership, decision points, quality gates, release criteria, and the evidence needed for audits or incident review.
References
Explore authoritative guidance and frameworks related to software development lifecycle (sdlc).
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