Loads Page Resources Using Protocol Relative URIs: How to Fix This Technical SEO Issue

Understanding Protocol Relative URIs

Definition and Purpose of Protocol Relative URIs

Protocol relative URIs are URLs that omit the protocol (http:// or https://) and start with double slashes (//). They emerged as a flexible solution during the early transition to HTTPS, allowing resources to load via either HTTP or HTTPS depending on the parent page’s protocol. However, this approach has become outdated and potentially risky in today’s web landscape.

As security experts now recommend, using explicit HTTPS URLs is the safer and more effective practice. Protocol relative URIs can expose users to attacks by allowing resources to load over unsecured HTTP connections. This vulnerability was highlighted in incidents like the Github Man-on-the-side attack, underscoring the importance of moving away from this outdated technique.

Advantages and Disadvantages in Web Development

While protocol relative URIs offered flexibility in the past, their drawbacks now outweigh any benefits. The main disadvantages include:

1. Security vulnerabilities from potential HTTP connections
2. Performance hits from TLS handshakes and additional URL resolutions
3. Potential breakage of JavaScript code relying on protocol detection
4. Triggering of browser security warnings and error messages

With HTTPS now widely supported and encouraged by search engines as a ranking factor, there’s little reason to continue using protocol relative URLs. The security and performance costs simply don’t justify their use in modern web development.

Impact on Page Load Performance

Protocol relative URIs can significantly slow down page load times. The primary culprits are:

1. TLS handshakes adding latency (up to 2 round-trips)
2. Additional URL resolutions as browsers determine protocols
3. Potential multiple redirections between HTTP and HTTPS

These performance penalties are particularly noticeable on mobile networks. Given that page speed is a crucial factor in both user experience and search engine rankings, eliminating protocol relative URIs can provide a tangible boost to your site’s performance and SEO.

SEO Implications of Protocol Relative URIs

How Search Engines Interpret Protocol Relative URIs

Search engines view protocol relative URIs through the lens of security and crawlability. When encountering these URLs, crawlers must resolve them to absolute URLs, potentially impacting crawl efficiency. Since HTTPS became a ranking factor, protocol relative URLs have been seen as a potential negative signal, as they may lead to insecure HTTP connections.

Potential Ranking Factors Affected

Several key ranking factors can be impacted when using protocol relative URIs:

1. HTTPS as a ranking signal
2. Duplicate content issues
3. User experience metrics
4. Crawl efficiency
5. Site security and trustworthiness

From a technical SEO perspective, protocol relative URLs can also break JavaScript code that tries to detect location protocols and may not be supported by older browsers, creating potential accessibility issues that indirectly affect rankings.

Case Studies of SEO Impact

Real-world examples demonstrate the SEO impact of protocol relative URIs. Websites using these URLs began experiencing negative ranking effects when HTTPS became a ranking factor. SEO crawlers have documented cases where protocol relative URLs caused crawling inefficiencies and duplicate content issues when both HTTP and HTTPS versions were accessible.

Additionally, major browsers generate security warnings when encountering protocol relative URLs, negatively impacting user experience metrics that influence rankings. These case studies highlight the importance of addressing protocol relative URIs as part of a comprehensive search engine optimization strategy.

Identifying Protocol Relative URIs on Your Website

Manual Inspection Techniques

To manually identify protocol relative URIs:

• Examine your website’s source code for resource references beginning with double slashes (//)
• Check JavaScript resource links, CSS resource links, and image src attributes
• Pay special attention to third-party resources and CDN links
• Review both HTML source and any JavaScript or CSS files
• Focus on resource loading elements like <script>, <link>, <img>, and <iframe> tags

Remember to check in both HTTP and HTTPS contexts, as protocol relative URLs inherit the protocol from the parent page.

Automated Tools for Detection

Several automated tools can help detect protocol relative URIs across your website:

• Sitebulb performs security audits specifically checking for protocol relative URIs
• Sitechecker offers automated scanning capabilities to identify protocol relative URL usage
• SEO crawlers like Screaming Frog can identify protocol relative links in your resources

These tools typically flag protocol relative URIs as security vulnerabilities and examine both the main HTML source code and linked resources.

Common Locations of Protocol Relative URIs

Protocol relative URIs commonly appear in:

• JavaScript resource links
• CSS resource links
• Image src attributes
• Third-party resources and CDN links
• <script>, <link>, <img>, and <iframe> tags
• The rendered DOM (Document Object Model)

Browser inspection tools like Google Chrome’s developer console can help identify these URLs in the rendered DOM.

Fixing Protocol Relative URIs: Best Practices

Converting to HTTPS-Only URLs

To convert protocol relative URIs to HTTPS-only URLs:

1. Replace URLs starting with ‘//’ with explicit ‘https://’ URLs
2. Verify HTTPS versions of resources are available
3. For unavailable HTTPS resources, either host a local copy, find an HTTPS-compatible alternative, or remove the resource
4. Pay special attention to third-party resources and CDN links

Implementing Content Security Policy (CSP)

Content Security Policy provides an additional layer of protection when fixing protocol relative URIs:

1. Configure your policy to only allow secure HTTPS connections for all resource types
2. Specify ‘https:’ as the required protocol for external domains
3. This creates a defense-in-depth approach, blocking attempts to load resources over insecure connections

When resources aren’t available over HTTPS, you’ll need to either host local copies, find HTTPS-compatible alternatives, or remove them to maintain security compliance with your CSP.

Updating Legacy Code and Third-Party Resources

When updating legacy code and third-party resources:

1. Identify resources not available over HTTPS
2. Host local copies, find HTTPS-compatible alternatives, or remove non-essential resources
3. Pay special attention to CDN-hosted content and third-party scripts
4. Use tools like Screaming Frog to identify protocol relative links in your resources
5. Examine third-party code for resource references beginning with double slashes

Remember, while protocol relative URLs were once a workaround for browser security dialogs, they’ve become an anti-pattern that should be eliminated from legacy code.

Loads Page Resources Using Protocol Relative Uris: How to Fix This Technical SEO Issue

Step-by-Step Guide to Resolving Protocol Relative URIs

Follow these steps to fix protocol relative URIs:

1. Audit all resource references in your codebase
2. Replace protocol relative URIs with explicit HTTPS URLs
3. Address resources not available over HTTPS
4. Implement a Content Security Policy requiring HTTPS connections
5. Use SEO crawlers to verify all protocol relative URLs have been converted

This systematic approach ensures comprehensive remediation of protocol relative URI issues.

Testing and Verifying Fixes

After implementing fixes:

1. Use SEO crawlers to verify changes
2. Check browser developer consoles for security warnings
3. Examine both HTTP and HTTPS versions of pages
4. Pay special attention to the rendered DOM
5. Address any remaining protocol-relative URLs, particularly in third-party resources

Thorough testing ensures complete resolution of protocol relative URI issues.

Monitoring SEO Performance Post-Implementation

After fixing protocol relative URIs:

1. Track key SEO metrics to ensure positive impact
2. Regularly scan for new protocol-relative URLs
3. Monitor browser console warnings and security alerts
4. Pay attention to performance metrics, especially page load times
5. Track search engine rankings and crawl behavior

Regular security audits should include checking for protocol-relative URLs in both the main HTML source and rendered DOM.