Search for a security scanner and you will find dozens of tools whose homepages all promise the same thing. Whether you're looking for a website security scanner free to run against a live app, or a dependency scanner for your codebase, the evaluation process below applies the same way. For a beginner, that is paralyzing. The trick is to ignore the marketing and evaluate scanners the way you would test-drive a car: with a short, structured trial on your own project. This guide gives you the criteria that actually matter and a repeatable process to compare a couple of candidates fairly, so you end up with a tool you will actually keep using.
What you will accomplish
You will define what you need, run a fair trial of one or two scanners on a real repository, and make a confident choice based on evidence from your own code rather than a feature grid.
Prerequisites
- A real project to test against, ideally one representative of what you build.
- A terminal and basic command-line comfort.
- An hour of focused time.
Step 1: Decide what you actually need to scan
Scanners specialize. Before comparing anything, write down which of these you need:
- Dependencies for known vulnerabilities, called software composition analysis.
- Your own source code for risky patterns, called static analysis.
- Secrets accidentally committed to the repo.
- Container images for vulnerable OS packages.
- A live website or web app for externally exploitable issues — this is where a free website security scanner (open-source DAST tooling) fits, separate from the dependency and source-code scanning this guide focuses on.
Most beginners should start with dependency scanning, since that is where the largest share of real risk lives. A tool that does that one thing well beats a suite that does everything poorly.
Step 2: Shortlist and install a free tier
Pick one or two candidates that offer a free tier or open-source version, so you can try before you commit. Install the first:
curl -sSfL https://get.safeguard.sh/install.sh | sh
sg --version
A tool you can install and run in a couple of minutes is already scoring points. If a scanner requires a sales call before you can even try it, note that as friction.
Step 3: Run each candidate on the same repository
Fairness matters. Run every candidate against the identical project so the comparison means something:
sg scan
Record three numbers for each tool: how long it took, how many components it resolved, and how many findings it produced. A scanner that resolves far fewer components than the others is probably missing transitive dependencies, which is a serious gap.
Step 4: Judge the noise, not just the count
More findings is not better. The best scanner is the one that surfaces the real issues without burying them under false positives. For each candidate, look at the top ten findings and ask how many are genuinely actionable. Pay special attention to whether the tool offers reachability, which tells you if a vulnerable function is actually called:
sg scan --reachable-only
A tool that can separate the five findings you must fix from the ninety-five you can defer will save you far more time than one that just prints a bigger list.
Step 5: Check the fix experience
Detection is half the job. See what each tool does after it finds something:
sg scan finding CVE-2024-21538 --explain
Good scanners tell you the fixed version, how the package entered your project, and ideally can propose or apply the fix. A tool that only says "you have a problem" leaves the hard part to you.
Step 6: Confirm it fits your workflow
Finally, make sure it fits where you work. Check that it runs in your CI pipeline with a clear pass or fail signal, and that local results match pipeline results:
sg scan --fail-on high
A scanner you can gate a build on, and that behaves the same on your laptop as in CI, is one you will actually keep running.
How to know it worked
- You have a short table comparing each candidate on speed, components resolved, and actionable findings.
- You know which tool produced the least noise for the real issues it caught.
- You confirmed at least one candidate explains and helps fix findings, not just detects them.
- Your top choice runs cleanly in CI with a fail-on threshold.
If your decision rests on numbers you gathered from your own repository, you chose well.
Next steps
- Roll out the winner to one project first, learn its quirks, then expand.
- Set a sensible fail threshold so the tool blocks serious findings without crying wolf.
- Learn the categories so you know what a scanner can and cannot do, via the concepts library.
- Revisit the choice yearly, since tools and your needs both evolve.
To understand the technique behind dependency scanning and why reachability matters so much in a comparison, read about software composition analysis. See how one CLI gives identical local and CI results, and compare what each tier includes on the pricing page. When you are ready to go deeper on evaluation, the Safeguard Academy has structured lessons.
Frequently Asked Questions
What kind of scanner should a beginner start with? Start with a dependency scanner, also called software composition analysis, because the majority of real risk in a typical application comes from open-source libraries rather than your own code. Once that is running smoothly, you can add source-code, secret, and container scanning as your needs grow.
Does more findings mean a better scanner? No, often the opposite. A scanner that floods you with low-value findings and false positives trains you to ignore it, which is worse than useless. The better tool is the one that reliably surfaces the genuinely exploitable issues and helps you tell them apart from the noise, for example with reachability analysis.
Should I pick a single tool that does everything or several specialized ones? Either can work, but for a beginner an integrated tool that covers your primary needs well is easier to operate than stitching several together. What matters most is depth on the category you care about most, usually dependencies, not the length of the feature list.
How do I run a fair comparison between scanners? Run every candidate against the same representative repository, and record the same metrics for each: scan time, components resolved, and how many of the top findings are actually actionable. Basing the decision on evidence from your own code beats trusting any vendor's feature grid.
Is a website security scanner free to use, or do I need to pay? Several open-source DAST tools can scan a live website for free, and they're worth trying if a public-facing web app is what you're worried about. Most free website security scanner tools need more manual tuning than a paid platform, so budget some setup time — but for the dependency and source-code scanning this guide focuses on, the free tier of an SCA tool (Step 2) is the better starting point.
Want to try a scanner on your own repository right now? Create a free account at app.safeguard.sh/register, and learn how to evaluate tools well in the Safeguard Academy.