Advanced CSP Evaluator
Analyze your Content Security Policy headers, identify vulnerabilities, and ensure your website is protected against XSS and data injection attacks.
Mastering Content Security Policy (CSP)
Protect your web applications from Cross-Site Scripting (XSS) and data injection attacks. Our Advanced CSP Evaluator helps you test, validate, and optimize your security headers for robust protection.
What is a Content Security Policy?
A Content Security Policy (CSP) is a critical computer security standard introduced to prevent Cross-Site Scripting (XSS), clickjacking, and other code injection attacks resulting from execution of malicious content in the trusted web page context.
It works by allowing site administrators to define exactly which dynamic resources are allowed to load. If a script or image isn't on the approved list (allowlist), the browser blocks it immediately.
Key Benefits
- Mitigates Cross-Site Scripting (XSS)
- Prevents Data Injection Attacks
- Controls Resource Loading
- Reports Security Violations
Why is CSP Crucial for Modern Web Security?
XSS Defense
XSS attacks occur when an attacker uses a web application to send malicious code, generally in the form of a browser side script, to a different end user. CSP is the primary defense.
Strict Governance
CSP imposes a strict governance structure on your frontend, ensuring that no unauthorized scripts, pixels, or analytics trackers can load without explicit permission.
Compliance & Trust
Implementing a robust CSP demonstrates a commitment to security, helping with compliance standards like PCI-DSS and building trust with your users.
How to Use the Advanced CSP Evaluator
Enter URL
Input the website address you want to analyze (e.g., https://google.com).
Analyze Headers
Our tool fetches the live headers and parses the Content-Security-Policy.
Review & Fix
Check your security grade, identify 'unsafe-inline' warnings, and missing directives.
Example Strong Policy
default-src 'self';
script-src 'self' https://trusted.cdn.com;
img-src 'self' data: https:;
style-src 'self' 'unsafe-inline';
object-src 'none';
base-uri 'self';Common CSP Error Codes & Fixes
Refused to load the script '...' because it violates the following Content Security Policy directive
Fix: Identify the blocked domain and add it to your `script-src` whitelist. If it's an inline script, consider using a nonce or hash.
Refused to apply inline style because it violates the following Content Security Policy directive: "style-src 'self'"
Fix: Avoid inline styles correctly. Move styles to external CSS files. If necessary, use `style-src 'unsafe-inline'`, though this reduces security.
Frequently Asked Questions (FAQ)
What is a Content Security Policy (CSP) and why do I need it?
Content Security Policy (CSP) is an added layer of security that helps to detect and mitigate certain types of attacks, including Cross-Site Scripting (XSS) and data injection attacks. You need it to ensure that only trusted content is executed on your website.
How do I fix 'Refused to load the script' CSP errors?
This error occurs when a script tries to load from a source not allowed by your CSP. To fix it, you need to add the domain to your `script-src` directive or use a nonce/hash for inline scripts.
What is the difference between `nonce` and `unsafe-inline`?
`unsafe-inline` allows all inline scripts, which significantly weakens security. A `nonce` (number used once) allows you to whitelist specific inline script blocks without allowing all of them, offering much better protection against XSS.
How does `strict-dynamic` improve CSP security?
`strict-dynamic` is a directive that allows scripts loaded by a trusted script (e.g., one with a valid nonce) to automatically be trusted as well. This simplifies CSP management for modern apps with many dependencies.
Can CSP prevent all XSS attacks?
While CSP is a very powerful defense, it is not a silver bullet. It should be used as part of a defense-in-depth strategy along with secure coding practices, input validation, and output encoding.
What is the `report-uri` or `report-to` directive?
These directives tell the browser where to send JSON data about CSP violations. This allows you to monitor your policy's effectiveness and identify new violations without breaking the site (if using Content-Security-Policy-Report-Only).
How do I allow Google Fonts or Analytics in CSP?
For Google Fonts, allow `https://fonts.googleapis.com` in `style-src` and `https://fonts.gstatic.com` in `font-src`. For Analytics, allow `https://www.google-analytics.com` in `script-src` and `connect-src`.
My CSP is blocking images/styles, how do I debug it?
Check your browser's console (F12) for the specific violation error. It will tell you which resource is blocked and which directive triggered it. Use a tool like this CSP Evaluator to visualize your policy.
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