CSP Score Calculator
Evaluate your Content Security Policy (CSP) robustness and XSS resilience instantly.
50.0%
-15.0%
+10.0%
Formula: Score = (Directives × 10) – (Unsafe Keywords × 15) – (Wildcards × 10) + (Strict Features × 20)
CSP Score Calculator Component Analysis
Comparison of current performance vs. industry security benchmarks.
| Metric Type | Description | Impact | Weight |
|---|---|---|---|
| Directive Coverage | Inclusion of core policies like default-src and script-src | Positive | 10 pts/ea |
| Unsafe Keywords | Use of ‘unsafe-inline’ or ‘unsafe-eval’ | Critical Negative | -15 pts/ea |
| Origin Restriction | Avoidance of wildcards (*) and broad patterns | Negative | -10 pts/ea |
| Modern Features | Use of Nonces, Hashes, and strict-dynamic | High Positive | 20 pts/ea |
What is a CSP Score Calculator?
The CSP Score Calculator is a specialized technical tool designed to audit the effectiveness of a Content Security Policy header. In modern web development, a CSP is your primary defense against Cross-Site Scripting (XSS) and data injection attacks. This CSP Score Calculator evaluates the syntax and strictness of your policy to determine if it truly protects your users or if it is simply “security theater.”
Security researchers, DevOps engineers, and web developers use a CSP Score Calculator to identify weak points in their security configuration. A high score indicates a “Default-Deny” posture that prevents unauthorized scripts from executing, while a low score reveals vulnerabilities that hackers can exploit. Many people believe having any CSP header is enough, but the CSP Score Calculator often reveals that permissive keywords make the policy practically useless.
CSP Score Calculator Formula and Mathematical Explanation
The CSP Score Calculator uses a weighted algorithm to translate policy directives into a numerical value. The math focuses on rewarding restriction and punishing over-permission. The core logic follows this derivation:
Score = Σ(Directive Points) – Σ(Penalty Points) + Σ(Bonus Points)
| Variable | Meaning | Unit | Typical Range |
|---|---|---|---|
| D | Directive Count | Integer | 3 – 12 |
| U | Unsafe Keyword Instances | Integer | 0 – 5 |
| W | Wildcard Definitions | Integer | 0 – 4 |
| S | Strict Mechanisms (Nonces/Hashes) | Integer | 0 – 3 |
Practical Examples (Real-World Use Cases)
Example 1: The “Loose” Legacy Policy
Imagine a website with the following policy: default-src *; script-src 'unsafe-inline' *; style-src 'unsafe-inline' *;. When we input these values into the CSP Score Calculator, we see 3 directives, 2 unsafe keywords, and 3 wildcards. The CSP Score Calculator would yield a score of approximately 15/100 (Grade: F). This tells the developer that despite having a header, the site is wide open to XSS because the wildcards allow scripts from any domain.
Example 2: The “Modern Strict” Policy
Consider a banking app with: default-src 'none'; script-src 'nonce-2726c' 'strict-dynamic'; style-src 'self'; img-src 'self';. Here, the CSP Score Calculator counts 4 directives, 0 unsafe keywords, 0 wildcards, and 2 strict features (nonce + strict-dynamic). The CSP Score Calculator would output a score of 95/100 (Grade: A+), confirming a world-class security posture.
How to Use This CSP Score Calculator
Getting the most out of the CSP Score Calculator involves four simple steps:
- Analyze Your Header: Locate your
Content-Security-PolicyHTTP response header using browser developer tools (Network tab). - Input Directive Counts: Count how many unique directives you have (like
connect-src,font-src) and enter them into the CSP Score Calculator. - Identify Red Flags: Check for keywords like
'unsafe-inline'or the*symbol. These are the primary factors that lower your CSP Score Calculator result. - Review the Grade: Look at the CSP Score Calculator‘s primary output. If you are below 70 (Grade C), you should prioritize removing inline scripts and restricting your source lists.
Key Factors That Affect CSP Score Calculator Results
1. Keyword Usage: The presence of 'unsafe-inline' is the biggest score killer. It allows any script directly in the HTML to run, bypassing the core purpose of CSP.
2. Wildcard Origins: Using * or https: as a source allows assets from any server. The CSP Score Calculator heavily penalizes this because it permits attackers to host malicious payloads on their own servers.
3. Object-src Restriction: If object-src is not set to 'none', the CSP Score Calculator may flag a risk related to legacy plugins like Flash or Silverlight.
4. Base-URI Control: Controlling the <base> tag prevents attackers from redirecting relative URLs to their own malicious domains.
5. Nonces and Hashes: These are “cryptographic signatures” for scripts. Using them provides a huge boost in the CSP Score Calculator because they prove exactly which scripts are authorized.
6. Strict-Dynamic Support: This modern directive makes CSP management easier while maintaining high security, which is why the CSP Score Calculator rewards its implementation.
Frequently Asked Questions (FAQ)
Why did the CSP Score Calculator give me a 0?
A zero score usually happens when the number of unsafe keywords and wildcards completely negates the protective value of your directives. It means your policy is technically active but offers no real protection against common attacks.
Is a 100/100 score always necessary?
While a high score on the CSP Score Calculator is ideal, some legacy applications require 'unsafe-inline' to function. In these cases, try to use hashes to mitigate the risk while keeping the application running.
Does the CSP Score Calculator check for syntax errors?
This specific CSP Score Calculator focuses on the logic and strength of the policy. For syntax validation, you should use a complementary tool to ensure colons and semicolons are correctly placed.
Can a high CSP score prevent all XSS?
No tool is a silver bullet. While the CSP Score Calculator helps you build a strong defense-in-depth, you still need to practice secure coding and output encoding.
What is ‘strict-dynamic’ in the CSP Score Calculator context?
It’s a directive that allows scripts authorized by a nonce to load additional scripts. The CSP Score Calculator rewards this as it’s the modern standard for balancing security and functionality.
How often should I use the CSP Score Calculator?
Run the CSP Score Calculator every time you add a new third-party library or change your site’s architecture to ensure you haven’t introduced security regressions.
Are data: URIs bad for my score?
Generally, yes. The CSP Score Calculator penalizes data: in script-src because it can be used to bypass XSS protections by injecting the script content directly into the URL.
What is a good score on this calculator?
Aim for a score above 80. A score of 80+ on the CSP Score Calculator usually means you have covered your core directives and avoided the most dangerous unsafe keywords.
Related Tools and Internal Resources
Explore our other technical assessment tools to bolster your security infrastructure:
- Security Audit Tool: A comprehensive scanner for web vulnerabilities beyond CSP.
- XSS Prevention Guide: Learn how to write code that complements your CSP policy.
- Header Security Checklist: A list of all essential HTTP headers like HSTS and X-Frame-Options.
- Web Security Metrics: Understand the KPIs that matter for cybersecurity professionals.
- Network Security Assessment: A tool for evaluating your server-side network configurations.
- SSL Score Calculator: Analyze the strength of your TLS/SSL certificates and cipher suites.