SDLC Models Explained: Types and How to Choose

There is no single best SDLC model for every project. Choose by asking whether requirements are stable, how complex and risky the work is, how much testing it needs, whether stakeholders can give frequent feedback, and what process the team can run well. Stable, well-defined work can suit Waterfall or the V-model; changing requirements often favor iterative approaches such as Agile; high-risk work may call for Spiral’s recurring risk analysis.

The software development life cycle (SDLC) describes the work involved in building, delivering, and maintaining software. A common view includes planning, analysis, design, coding, testing, deployment, and maintenance. An SDLC model describes how that work is organized and revisited; it does not change the underlying need to do it. IBM’s SDLC overview describes these phases and common models.

SDLC models at a glance

Model	How work proceeds	Consider it when	Main tradeoff
Waterfall	Work moves through sequential stages, completing one before moving to the next.	Requirements are clear and expected to remain stable.	Revisiting a completed stage can be difficult and time-consuming.
V-model	A Waterfall-style lifecycle pairs development phases with corresponding testing phases.	Requirements are stable and testing needs to be planned throughout.	It retains a linear structure, which limits flexibility.
Agile	Work is delivered in small increments with regular discussion, review, and adaptation.	Requirements may change and stakeholders can give frequent input.	It depends on ongoing collaboration and feedback.
Iterative	The team creates an initial version, then refines it in successive cycles.	Learning from each version can improve the next one.	Teams need to manage changes and keep each cycle focused.
Spiral	Each cycle sets objectives, analyzes resources and risks, develops and tests, then plans the next cycle.	The project is complex or high-risk and change is expected.	Risk analysis is a central, recurring part of the process.
Lean	The team applies waste reduction and continuous improvement to development.	Reducing process waste and shortening feedback loops matter.	The team must identify waste without losing necessary quality work.
RAD	Rapid prototypes and user feedback guide development instead of a long initial planning period.	User needs should be tested and adapted quickly.	It relies on feedback that can guide prototype changes.
Big bang	Work proceeds with minimal structure and little upfront planning.	A small project has self-explanatory parameters.	IBM characterizes it as high-risk; limited planning leaves more uncertainty.

These descriptions follow IBM’s qualitative model guide. They are tradeoffs, not guarantees of project outcomes. IBM’s SDLC models guide provides further descriptions.

How to choose an SDLC model

Check requirement stability. Are requirements clearly defined, or likely to change during development? Stable requirements can support Waterfall or V-model. Expected change and regular stakeholder input point toward iterative work, including Agile.
Assess complexity and risk. For high-risk or complex work where change is expected, consider Spiral because risk analysis recurs in each cycle.
Set the testing emphasis. The V-model makes testing phases explicit alongside lifecycle phases. Account for its linearity when requirements may change.
Confirm feedback availability. Agile and RAD depend on discussion, reviews, or user feedback. If stakeholders cannot participate regularly, consider how the team will get the information needed to adapt.
Match the process to the team. Team experience is a selection factor. Consider whether the team can maintain the chosen level of structure, collaboration, and review. Lean is relevant when reducing waste and improving feedback are important.

This is a decision sequence, not a scoring formula. Compare flexibility, process structure, testing needs, feedback frequency, and risk handling together. IBM identifies requirement stability, complexity, and team experience as selection considerations; the remaining comparison points follow from the models’ described practices. IBM’s overview and its Agile and Waterfall comparison discuss these factors.

Understand the models and their tradeoffs

Waterfall: sequential and structured

Waterfall organizes work as a linear sequence: a stage is completed before the next begins. This structure can suit clearly defined, stable work. Its limitation is change: returning to a completed stage can be difficult and time-consuming. Consider how likely requirement changes are before selecting it.

V-model: testing mapped to development

The V-model is a Waterfall variation in which lifecycle phases have corresponding testing phases. It can be useful when requirements are stable and testing needs to be planned frequently. Its linear structure still limits flexibility, so it may be a poor fit when the team expects substantial changes.

Agile: incremental work with feedback

Agile develops in small increments and makes room for regular discussion and review. It suits work where stakeholders can provide frequent input and requirements may change. Scrum and Kanban are common frameworks associated with Agile, but they are not synonyms for all SDLC models: Scrum organizes work into time-boxed sprints, while Kanban uses a continuous workflow and visible task board.

Iterative: refine a version in cycles

An iterative approach begins with an initial version and improves it over successive cycles. It is useful when the team can learn from each version and build outward. Agile also uses repeated cycles, with particular emphasis on incremental changes and stakeholder feedback.

Spiral: make risk analysis part of each cycle

Spiral repeats objective-setting, resource and risk analysis, development and testing, and planning for the next iteration. Its recurring risk analysis makes it a candidate for complex or high-risk work where change is expected.

Lean: reduce process waste and improve continuously

Lean applies waste-reduction and continuous-improvement principles to development. It emphasizes quality practices and faster feedback while reducing process waste. Consider it when improving the flow of work is a central process goal.

RAD: learn through rapid prototypes

Rapid application development (RAD) uses rapid prototyping and user feedback rather than a long initial planning period. It can suit projects where user needs must be tested and adapted quickly.

Big bang: minimal structure, high risk

Big bang uses little upfront planning and minimal structure. IBM describes it as high-risk and potentially suitable for small projects with self-explanatory parameters. Treat the risk as a defining tradeoff, not as a shortcut that fits any deadline.

SDLC model or Agile framework?

An SDLC model describes how the lifecycle’s work is arranged. Agile is an iterative development approach; Scrum and Kanban are frameworks commonly associated with Agile. Scrum uses time-boxed sprints. Kanban supports continuous workflow with a visible task board. Naming a framework does not, by itself, explain how every phase of a project will be planned, tested, deployed, and maintained.

Practical selection checklist

Requirements: Are they clear and stable, or likely to change?
Complexity and risk: Does the work need risk analysis to recur throughout development?
Testing: Should testing phases be mapped explicitly to development phases?
Feedback: Can stakeholders or users review work often enough to guide changes?
Team experience: Can the team sustain the process and collaboration the approach requires?
Structure: Does the project need a defined sequence, or would cycles and adaptation fit better?

If answers point in different directions, write down the most important constraint and the tradeoff the team accepts. The researched guidance does not establish a universal winner or a numerical threshold for choosing one model.

Applying an SDLC model to a website capture feature

A website capture feature makes a concrete example. The lifecycle still includes planning, analysis, design, coding, testing, deployment, and maintenance; the model changes how the team schedules and revisits that work. Under Waterfall, a team could define stable capture requirements and proceed through stages in sequence. With Agile or an iterative approach, it could deliver an initial capture flow, gather feedback, and refine later cycles. With Spiral, it could revisit risks such as timeouts or incomplete pages in each cycle. These are illustrations of the models’ structure, not claims about a particular team or outcome.

For manual browser work, a developer can use browser automation to open a page and save a screenshot. The example below uses Playwright’s documented Python API. Install Playwright and its browser first, then save the script as capture.py and run python capture.py.

from pathlib import Path
from playwright.sync_api import sync_playwright

TARGET_URL = "https://example.com"
OUTPUT = Path("page.png")

with sync_playwright() as playwright:
    browser = playwright.chromium.launch(headless=True)
    page = browser.new_page(viewport={"width": 1440, "height": 900}, device_scale_factor=1)
    response = page.goto(TARGET_URL, wait_until="networkidle", timeout=60_000)
    if response is None or not response.ok:
        status = response.status if response else "no response"
        browser.close()
        raise RuntimeError(f"Navigation failed: {status}")
    page.screenshot(path=str(OUTPUT), full_page=True)
    browser.close()

print(f"Saved {OUTPUT}")

Install with python -m pip install playwright and python -m playwright install chromium. The script checks the navigation response, uses a fixed viewport, waits for network idle, saves the full page, and closes the browser. Some sites keep network connections open, so network idle may never occur; in that case use a deliberate selector wait or a bounded delay suited to the page instead. Full-page screenshots can also be very tall and consume more memory than viewport captures. Consult the Playwright screenshot documentation for screenshot options and the navigation API for load-state behavior.

cURL, Python requests, and Node.js alternatives

When the task is to save a rendered page through ScreenshotNeo’s screenshot API, these runnable request examples use the provided endpoint and API key placeholder. The response body is the image. See the ScreenshotNeo API documentation for request configuration.

curl -G "https://api.screenshotneo.com/v1/shot" \
  -d access_key=YOUR_API_KEY \
  --data-urlencode url=https://example.com \
  -o shot.webp

import requests

r = requests.get(
    "https://api.screenshotneo.com/v1/shot",
    params={"access_key": "YOUR_API_KEY", "url": "https://example.com"},
    timeout=90,
)
r.raise_for_status()
with open("shot.webp", "wb") as output:
    output.write(r.content)

const q = new URLSearchParams({
  access_key: 'YOUR_API_KEY',
  url: 'https://example.com'
});
const res = await fetch(`https://api.screenshotneo.com/v1/shot?${q}`);
if (!res.ok) throw new Error(`Screenshot request failed: ${res.status}`);
await import('node:fs/promises').then(fs => fs.writeFile('shot.webp', Buffer.from(await res.arrayBuffer())));

Or skip the browser setup

ScreenshotNeo is a website screenshot API and MCP server. One GET request can return a PNG, JPEG, WebP, or PDF. Cookie banners are accepted and removed before capture, and 60+ known consent platforms, newsletter popups, and chat widgets can be removed; each step can be turned off. Bot checks, blank pages, timeouts, failed loads, and cache hits cost nothing, with response headers indicating the page verdict and billing status. Its MCP server provides take_screenshot, get_page_info, and capture_pdf tools for Claude, Cursor, and other MCP clients. The Free plan includes 1,000 screenshots per month with no card; paid plans start at $5 for 3,000 screenshots.

curl -G "https://api.screenshotneo.com/v1/shot" \
  -d access_key=YOUR_API_KEY \
  --data-urlencode url=https://example.com \
  -o shot.webp

See the API docs for options and sign up for 1,000 free screenshots a month, with no card.

Common capture problems and fixes

Symptom	Likely cause	What to try
Navigation times out	The page is slow, or persistent requests prevent the selected load condition from completing.	Check that the URL is reachable, raise the timeout within a reasonable bound, or wait for a page-specific selector instead of network idle.
The screenshot is blank or incomplete	The page may not have rendered its content when capture ran, or content may require scrolling or interaction.	Wait for a meaningful selector, scroll to trigger lazy loading, or use a bounded delay. Check the page’s response and console behavior.
Some images are missing	Images may load lazily or after the initial page render.	Scroll through the page before capturing and allow the images to load; verify the result at the chosen viewport.
Browser launch fails	The Playwright browser binaries may not be installed in the environment.	Run `python -m playwright install chromium` and confirm the environment permits launching a headless browser.
Screenshot dimensions are unexpectedly large	A full-page capture includes the complete document height; device scale factor also affects pixel dimensions.	Use a viewport capture if a single screen is sufficient, reduce the viewport or scale factor, or capture a specific element.
API request returns an error	The key may be missing or invalid, the URL may be malformed, or the request may exceed the client timeout.	Check the endpoint, key, URL encoding, HTTP status, and request timeout. Consult the API docs for response details.

Performance, reliability, and cost considerations

Browser runtime: Launching a browser and loading a page takes more resources than saving a static file. Reuse a browser process for multiple captures when your automation setup allows it, and close pages and browsers when finished.
Wait strategy: Waiting for network idle can be useful for pages that settle, but ongoing connections can make it unreliable. Prefer a meaningful selector when the capture depends on a specific component, and keep timeouts bounded.
Capture size: Full-page captures and high device scale factors increase image dimensions and memory use. Choose full-page output only when the entire document is needed.
Repeatability: Fix the viewport and relevant browser settings when comparing captures. Dynamic content, animations, time-dependent pages, and user-specific state can still change results.
Failure handling: Check navigation and HTTP status, use explicit timeouts, and handle failures so a partial image is not mistaken for a successful result. Retry only transient failures and avoid unbounded retry loops.
API cost: ScreenshotNeo bills clean shots; bot checks, CAPTCHA pages, blank pages, timeouts, failed loads, and cache hits are not billed. Its published plans are Free: 1,000 per month; Starter: $5 for 3,000; Growth: $15 for 15,000; Pro: $39 for 60,000; Scale: $99 for 250,000; and Business: $249 for 1,000,000. Yearly billing gives two months free, and every feature is available on every plan. See the docs for current API behavior.

FAQ

What does SDLC stand for?

Software development life cycle: the structured work of building, delivering, and maintaining software.

Is Agile itself an SDLC model?

Agile is an iterative development approach associated with SDLC work. Scrum and Kanban are common Agile frameworks, each organizing workflow differently.

Can a project use more than one model?

The researched guidance compares common models but does not prescribe a universal hybrid. Describe the actual process the team will follow and ensure responsibilities for testing, feedback, risk, and delivery are clear.

Which model is best for a small project?

Project size alone is not enough to choose. Big bang is described as potentially suitable for small projects with self-explanatory parameters, but it carries high risk. Also consider requirement stability, complexity, testing, and available feedback.

Does the V-model mean testing only happens at the end?

No. Its defining idea is that lifecycle phases have corresponding testing phases, though its overall structure remains linear.