SRI Hash Generator

What is Subresource Integrity (SRI)?

Subresource Integrity (SRI) is a vital security feature that enables web browsers to verify that the files they fetch (such as JavaScript libraries or CSS stylesheets) are delivered without unexpected manipulation. By providing a cryptographic hash, SRI ensures your site only executes scripts that match your exact specifications. If you want to dive deeper into web security, check out our Pillar Guide on Web Security Best Practices.

Why You Need SRI for CDN-Hosted Files

When you load scripts from a third-party CDN, you implicitly trust that the CDN has not been compromised. However, supply chain attacks are increasingly common. If a hacker alters a library on the CDN, every site using that library becomes compromised. Using an SRI Hash Generator ensures the browser cross-checks the file against your known-good hash before execution. If the file is modified by even a single byte, the browser blocks it. For other security tasks like securing passwords in your backend, explore our Bcrypt Hash Verifier.

How to Implement SRI Hashes

Implementing SRI requires generating a Base64-encoded cryptographic digest of the file's contents. You can encode or decode strings directly using our Base64 Encoder/Decoder if needed. You then append the integrity attribute to your <script> or <link> tag. The crossorigin="anonymous" attribute is also required for files fetched from different origins. For handling cryptographic keys locally, you might also find our UUID Generator helpful for distinct session management.

<script src="https://example.com/library.js" 
integrity="sha384-oqVuAfXRKap7fdgcCY5uykM6+R9GqQ8K/uxy9rx7HNQlGYl1kPzQho1wx4JwY8wC" 
crossorigin="anonymous"></script>

Best Practices

• Use Strong Algorithms: SHA-384 is the W3C recommended standard as it offers a great balance of speed and security.
• Pin Versions: Always include the exact version number in the CDN URL (e.g., v1.2.3 instead of latest). The `latest` tag will change over time, breaking your SRI hash.
• Cross-Origin Configuration: Always include crossorigin="anonymous" when fetching scripts from a different domain to ensure the browser properly applies the integrity check.

Troubleshooting SRI Failures

If a script fails to load and the browser console throws an SRI error, the file served by the URL does not exactly match the hash provided. Check the following:

• Whitespace and Minification: Ensure the file hasn't been auto-minified by the CDN. Even a missing space or newline will change the hash.
• Line Endings: Differences between CRLF (Windows) and LF (Unix) line endings will completely change the hash. Ensure you hash the exact file being served.
• Dynamic Content: Some hosting providers inject analytics or timestamps into scripts dynamically. This breaks SRI.

Browser Compatibility

Subresource Integrity is widely supported across all modern web browsers, including Chrome, Firefox, Safari, and Edge. In older browsers that do not support SRI, the integrity attribute is simply ignored, and the script loads normally, ensuring progressive enhancement without breaking functionality.

Privacy Policy & Data Security

This SRI Hash Generator is a completely client-side application. All cryptographic hashing is performed locally in your browser using the native Web Crypto API. We do not transmit, log, or store the JavaScript or CSS code you paste into the tool. Your proprietary code remains 100% private.