SAST vs DAST vs IAST: Complete Comparison Guide (2026)

Three approaches, one goal

No single testing method catches everything. That is the uncomfortable truth behind application security testing, and it is the reason three distinct approaches exist.

• SAST (Static Application Security Testing) reads your source code and finds flaws before the application runs.
• DAST (Dynamic Application Security Testing) attacks your running application from the outside, the way a real attacker would.
• IAST (Interactive Application Security Testing) places an agent inside your running application and watches what happens during testing.

They differ in what they analyze, when they run, and what they catch. A SQL injection that SAST flags in your code might be one that DAST confirms is actually exploitable at runtime. An IAST agent can tell you both that the vulnerability exists and exactly which line of code is responsible.

This guide breaks down how each method works, what it catches, and how to figure out which combination your team actually needs.

What is SAST?

Static Application Security Testing analyzes source code, bytecode, or binaries without executing the application. White-box testing, in other words. The tool has full visibility into your codebase.

SAST tools parse your code into an abstract syntax tree, then apply rules and analysis techniques to spot vulnerabilities. The better tools go well beyond pattern matching. They trace data flow from user input (sources) through your code to dangerous operations (sinks), catching injection flaws that simple regex searches would miss.

A concrete example: a SAST tool scanning a Java web application might trace data from an HttpServletRequest.getParameter() call through several method invocations to a Statement.executeQuery() call, flagging it as a potential SQL injection if no sanitization occurs along the way.

SAST runs during development, in your IDE, or in CI pipelines on every pull request. It catches SQL injection, cross-site scripting, buffer overflows, hardcoded secrets, insecure cryptography, and other code-level flaws.

What it cannot see: runtime configuration issues, authentication bypass, server misconfigurations, and business logic flaws that only show up when the application is actually running.

Popular SAST tools include Checkmarx, SonarQube, Semgrep, Snyk Code, Fortify, Veracode, GitHub CodeQL, Bandit (Python), and Brakeman (Ruby on Rails). See our SAST tools category page for a full comparison.

What is DAST?

Dynamic Application Security Testing tests a running application from the outside. No source code required. The tool crawls your web application, discovers endpoints, and fires malicious payloads at them to see what breaks.

This is black-box testing. The scanner behaves like an attacker, probing for SQL injection, XSS, and other OWASP Top 10 issues by watching how the application responds to crafted inputs.

Say a DAST tool is testing a login page. It submits ' OR 1=1-- as the username and watches for a database error in the response. If it gets one, that is a confirmed SQL injection, not a theoretical one.

DAST runs against staging or pre-production environments. Some lightweight tools can run on every pull request if you deploy to an ephemeral environment. Full crawl scans typically run nightly or weekly.

It catches runtime vulnerabilities, server misconfigurations, missing security headers, authentication and session management issues, and problems in third-party components or infrastructure that source code analysis cannot reach.

The trade-off: DAST tells you a vulnerability exists at a particular URL, but it cannot point to the exact file and line in your source code. It also depends on crawl coverage, so pages behind complex navigation or authentication flows may get missed.

Popular DAST tools include Burp Suite, ZAP, Invicti, Nuclei, HCL AppScan, StackHawk, Veracode DAST, and Dastardly. See our DAST tools category page for a full comparison.

What is IAST?

Interactive Application Security Testing is the hybrid approach. An agent lives inside your application runtime and observes code execution as the application handles requests during functional testing, whether manual or automated.

Grey-box testing, in other words. The agent sees both the source code being executed and the runtime behavior. You get the code-level precision of SAST with the runtime context of DAST.

When a test sends a request to your application, the IAST agent traces that request through your code. It watches untrusted input flow from an HTTP parameter through method calls, framework middleware, and eventually into a database query or file operation. If the input reaches a dangerous function without sanitization, the agent reports the vulnerability with the exact file, line number, and full call stack.

IAST runs during QA or integration testing. The agent sits passively alongside your test suite. More test coverage means more code paths observed. It catches the same vulnerability types as SAST (injection, XSS, etc.) but with runtime confirmation that the code path is actually reachable, which is why false positive rates are so low.

The catch: IAST only sees code paths that your tests exercise. If no test triggers a particular endpoint, the agent never observes it. Agent deployment also adds complexity for containerized and serverless architectures.

Popular IAST tools include Contrast Assess, Datadog IAST, HCL AppScan IAST, Invicti Shark, Checkmarx IAST, and Seeker. See our IAST tools category page for a full comparison.

Side-by-side comparison

The table below puts all three methods next to each other across the dimensions that matter most.

No single column is all green. Each method has trade-offs, and those trade-offs are why the three approaches exist as separate categories.

Where each fits in the SDLC

When you run each method matters as much as which method you pick.

SAST: Code and build phase

SAST runs earliest. Developers get feedback in their IDE or on pull requests within minutes. This is the “shift left” that everyone talks about, and it works because fixing a vulnerability during development is orders of magnitude cheaper than fixing it in production.

Typical integration points:

1. IDE plugins for real-time scanning as developers write code (Snyk Code, SonarLint)
2. Pre-commit hooks for lightweight checks before code is pushed (Semgrep, Bandit)
3. CI pipeline gates that block merges when critical findings appear (Checkmarx, SonarQube)

DAST: Testing and staging phase

DAST needs a running application, so it runs later in the pipeline. Most teams deploy to a staging environment and trigger DAST scans as part of their release process.

Typical integration points:

1. Quick scans on PRs using lightweight tools that finish in minutes (Dastardly, ZAP baseline scan)
2. Nightly full crawls against staging that run in the background (Invicti, HCL AppScan)
3. Pre-release gates that block production deployment on critical findings

IAST: QA and integration testing phase

IAST runs during your existing test suite execution. The agent observes what happens when tests interact with the application, so it produces results only when tests run.

Typical integration points:

1. Integration test suites where the agent runs alongside your automated tests
2. QA cycles where manual testers exercise the application with the agent installed
3. Staging environments where the agent runs continuously alongside DAST

These methods are not competing for the same slot in your pipeline. They run at different times and catch different things.

Detection capabilities

Not every vulnerability type is equally suited to every testing method. This table shows where each approach is strong and where it falls short.

A few things stand out in this table. No method handles business logic flaws well, because those require understanding the application’s intended behavior. Vulnerable dependencies are covered by SCA tools, not by any of these three approaches. And server-side configuration issues are DAST territory, since SAST and IAST work at the code level.

False positives and noise

False positives are the reason many security programs fail. If developers get flooded with findings that turn out to be noise, they stop paying attention.

SAST has the highest false positive rate of the three. It analyzes code statically, without knowing whether a particular code path is actually reachable at runtime or whether input validation occurs in a framework layer the tool does not model. Enterprise SAST tools use deep data flow analysis to reduce this, but tuning is still required. Industry estimates put SAST false positive rates at 30-60% for untuned tools.

DAST has a lower false positive rate because it tests real application behavior. If a DAST tool reports a SQL injection, it means the application actually returned a suspicious response to a malicious input. Some tools, like Invicti, use proof-based scanning to automatically confirm vulnerabilities, which pushes the false positive rate close to zero for confirmed findings.

IAST has the lowest false positive rate. The agent watches untrusted data flow through actual code execution paths, so it knows both that a vulnerability exists in the code and that the vulnerable code path is triggered by real requests. Contrast Security reports that their IAST approach produces significantly fewer false positives than traditional SAST or DAST.

If your team is drowning in false positives from SAST, the answer is not to drop SAST. Tune your rules, write custom rules for your frameworks, and consider adding IAST to validate findings.

Which should you choose?

The right combination depends on your team size, budget, and how mature your security program already is.

Small team, limited budget

Start with SAST. Pick a free tool that supports your language stack:

• Python: Bandit
• Ruby on Rails: Brakeman
• Multi-language: Semgrep or SonarQube Community Edition

Add DAST when you have a staging environment: ZAP or Nuclei cost nothing and integrate into CI.

Skip IAST for now. It adds the most value when you already have strong test automation.

Mid-size team, some budget

Run SAST and DAST together. SAST in CI for fast developer feedback. DAST against staging for runtime validation.

Consider commercial SAST (Checkmarx, Snyk Code, Veracode) if your team needs better triage, IDE integration, or compliance reporting. For DAST, StackHawk or Burp Suite Enterprise handle CI/CD integration well.

Evaluate IAST if you have a mature QA process with good test automation. Contrast Assess offers a free Community Edition to test with.

Enterprise team, full budget

Use all three. Layer them across your SDLC:

1. SAST in CI on every pull request
2. IAST during QA and integration testing
3. DAST against staging before every release

Add SCA for dependency scanning. Add RASP for production runtime protection of your most critical applications.

At this scale, consolidated platforms like Checkmarx One, Veracode, or HCL AppScan that offer SAST + DAST + IAST + SCA in a single dashboard simplify management and correlation.

Using all three together

When you run all three, the methods reinforce each other. Here is what that looks like in practice.

A developer pushes code with a SQL injection vulnerability. SAST flags it on the pull request within minutes. The developer fixes it before the code merges.

Later, the nightly DAST scan against staging discovers that a certain endpoint returns verbose error messages containing database schema details. SAST could not have caught this because it is a server configuration issue, not a code flaw.

During the QA cycle, the team runs integration tests with the IAST agent active. It catches a cross-site scripting vulnerability that SAST had reported as a potential issue but could not confirm. IAST confirms it is exploitable because the agent watched the tainted input pass through the code without sanitization.

When a finding appears in both SAST and DAST (or SAST and IAST), you know it is real. Some platforms correlate findings across methods automatically, which is one of the selling points of unified tools like Checkmarx One and HCL AppScan 360.

The question is whether the coverage improvement justifies the cost and complexity. For most organizations, SAST plus DAST covers 80-90% of what automated tools can find. Adding IAST narrows the remaining gap, mainly through false positive reduction.

Tool recommendations by category

Best free SAST tools

• Semgrep — 20+ languages, easy custom rules, active community. Probably the best all-around free SAST option right now.
• SonarQube Community Edition — 35+ languages, quality gates, wide CI/CD integration. Works well if you want code quality and security in one tool.
• Bandit — Python-specific. If Python is your primary language, this is the fastest way to get started.
• Brakeman — Ruby on Rails-specific. Deep framework awareness makes it accurate for Rails apps.

Best free DAST tools

• ZAP — The most widely used open-source DAST tool. Now maintained by Checkmarx. Works for both manual testing and CI/CD automation.
• Nuclei — Template-based scanner with 9,000+ community templates. Fast and precise, especially for targeted scanning.
• Dastardly — Free CI/CD scanner from PortSwigger (makers of Burp Suite). The 10-minute scan cap makes it practical for pipelines.

Best commercial platforms

• Checkmarx One — Unified SAST + SCA + DAST + IAST. Gartner Leader seven times.
• Snyk — Developer-first SAST and SCA with fast IDE feedback. Good fit for teams that care about developer experience.
• Invicti — Proof-based DAST scanning that scales to thousands of applications. Low false positive rate.
• Veracode — SAST + DAST + SCA in one platform. Gartner Leader. Binary analysis means no source code upload needed for SAST.

Best IAST tools

• Contrast Assess — Market leader in IAST. Free Community Edition available. Supports Java, .NET, Node.js, Go, Python.
• Datadog IAST — Makes sense if you already use Datadog for APM. Scores 100% on the OWASP Benchmark.

FAQ

Written by

Suphi Cankurt

Suphi Cankurt works at Invicti Security and has spent over 10 years in application security. He reviews and compares AppSec tools across 10 categories on AppSec Santa. Learn more.