When the Security Header Checker seems to misbehave, the cause is usually one of two things: something stopped the tool from running, or it ran but the result is not usable. This guide starts with the fastest checks, then walks through the common problems and exact fixes.
Quick Checks First
- Refresh the page - a stalled session is the most common cause of nothing happening.
- Confirm the input is not empty and actually contains what you meant to submit.
- Try the smallest possible input; if that works, the issue is size, not the tool.
- Turn off browser extensions that block scripts, then reload and test again.
- Update or switch browsers if the problem repeats across sessions.
Common Problems and How to Fix Them
A header I expected is missing.
Add it in your server or host configuration, then rescan to confirm the value the server now returns.
My content security policy blocks scripts.
Start with a reporting policy, list the origins you actually use and tighten it gradually to avoid breaking pages.
The report shows a different set of headers.
Redirects and caching can change what is returned - check the final URL and try again without a cached copy.
Strict transport security is flagged as absent.
Enable it only over HTTPS first and start with a short max age while you confirm every subdomain is ready.
I do not know which headers matter.
Start with transport security, frame options and a content security policy - they cover the most common browser side risks.
Headers differ between pages.
That is common with mixed setups, so check the important templates such as login and checkout individually.
When It Works but the Output Is Poor
If the tool runs fine but the result misses, the problem is almost always the brief, not the software:
- Assuming a missing header breaks the site
- Enabling a strict policy without testing
- Checking only the homepage
- Confusing a redirect with the final response
How to Stop It Happening Next Time
- Keep a saved prompt template for every task you repeat.
- Change one setting per generation so causes stay obvious.
- Run a two-minute sanity test with known input after any update.
- Note every failure and its fix; a short troubleshooting log pays for itself.
Still Stuck?
Reproduce the problem with the smallest possible input and note the exact steps that triggered it. A one-line description of what you did, what you expected and what happened is enough to get a precise answer from support or a colleague.
Frequently Asked Questions
Which headers should I start with?
Strict transport security, frame options and a content security policy cover the most common risks for most sites.
Will a strict policy break my site?
It can if it blocks scripts or frames you rely on, so roll it out gradually and test the main templates first.
Does this change my server settings?
No - it only reports what the server sends, and you make any changes in your own configuration.
Is my URL stored?
No - the check runs on demand with nothing retained.
Related Guides
- Security Header Checker - free online tool
- How to Use Security Header Checker
- What Is a Security Header Checker and How Does It Work?
- Security Header Checker Examples: Real Scenarios and Results
- Security Header Checker for Site Owners and Security-minded Users
- Best Security Header Checker Alternatives Worth Trying
- Security Header Checker Tips and Best Practices
- Is Security Header Checker Safe? Free vs Paid
- More security checkers and guides