If you’ve ever encountered the message “HTTP Version Not Supported (Error 505)”, you’re dealing with a server-side issue that can interrupt your website’s performance.
While it may sound complicated, understanding what causes Error 505 — and how to fix it — is key to maintaining a healthy, SEO-friendly website.
In this article, we’ll break down what Error 505 means, how it impacts your SEO, and the practical steps to resolve it.
What Does Error 505 Mean?
Error 505 — officially called “HTTP Version Not Supported” — appears when a web server refuses to support the HTTP protocol version used in a client’s request (e.g., from a browser or application).
In simple terms:
The browser is speaking one “language version,” but the server doesn’t understand it.
Common causes include:
- The server is outdated or misconfigured.
- The client (browser, API, or software) uses an unsupported HTTP version (like HTTP/1.1 or HTTP/2).
- Issues with proxy or gateway configurations.
- Hosting environment conflicts after updates.
How Error 505 Affects SEO and Website Performance
Although Error 505 is a technical server error (5xx class) and not directly penalized by Google, it can still hurt SEO indirectly by:
- 📉 Affecting Crawling & Indexing: Search engines can’t access your pages, marking them as temporarily unavailable.
- 🚫 Increasing Bounce Rates: Users leave when a page fails to load.
- 🧭 Wasting Crawl Budget: Frequent 5xx errors make Googlebot crawl your site less efficiently.
If your site repeatedly shows 505 or similar server errors (500, 502, 503), Google may reduce your domain’s crawl rate and visibility.
How to Diagnose Error 505
1. Check Server Logs
Inspect your server’s error logs (e.g., via cPanel, WHM, or your hosting dashboard) to identify where and when the 505 error occurs.
2. Test HTTP Versions
Use command-line tools like:
curl -I -v –http2 https://yourwebsite.com
If the server returns a 505, it means the HTTP version negotiation failed.
3. Use Online Tools
Platforms like:
- GTmetrix
- Pingdom
- HTTP Status Checker
can confirm whether a page is returning a 505 response code.
How to Fix HTTP Error 505
1. Update Server Software
Make sure your web server (Apache, Nginx, LiteSpeed, etc.) supports the latest HTTP versions.
For instance:
- Apache: enable
mod_http2 - Nginx: enable
http2directive in server block
2. Verify Configuration Files
Check for protocol limitations in:
.htaccess(Apache)nginx.conf(Nginx)- Reverse proxy or load balancer settings
Ensure these don’t restrict certain HTTP versions.
3. Restart the Server
Sometimes, after updates or misconfigurations, a simple restart resolves temporary handshake errors between browser and server.
4. Check for Proxy or CDN Conflicts
If you use Cloudflare or another CDN, disable it temporarily to test if the error persists.
Sometimes CDN caching or protocol translation causes HTTP version mismatch.
5. Contact Your Hosting Provider
If none of the above works, reach out to your hosting provider’s support team.
Provide:
- Timestamp of error
- Affected URLs
- Browser and device used
They can check server logs or firewall restrictions.
Preventing Future 505 Errors
- Keep your web server software up to date.
- Regularly test HTTP/2 and HTTP/3 support after system updates.
- Monitor 5xx errors through Google Search Console → Crawl Stats.
- Use uptime monitoring tools (like UptimeRobot or StatusCake).
- Avoid outdated APIs or client libraries in your codebase.
Final Thoughts
HTTP Error 505 might seem rare, but when it appears, it’s a clear signal your server and browser are out of sync.
By keeping your server updated, verifying configurations, and monitoring technical performance, you can ensure both visitors and search engines access your site smoothly.
At Mono Digital, we specialize in technical SEO, hosting optimization, and server-level performance tuning — helping businesses eliminate downtime and boost search visibility.
👉 Facing server or SEO issues? Contact Mono Digital to optimize your site’s health.