Encountering the dreaded net::ERR_HTTP2_PROTOCOL_ERROR can be a frustrating experience while browsing the web. This cryptic message, often appearing in Chrome and other Chromium-based browsers, signals a problem with the HTTP/2 protocol, the modern standard for transferring data over the internet. While seemingly technical, understanding the root causes of this error and applying practical troubleshooting steps can quickly restore your browsing experience. This error indicates that something went wrong during the communication between your browser and the web server, specifically when using the HTTP/2 protocol. We’ll explore common reasons for this error, from server misconfigurations to browser issues, and equip you with the knowledge to diagnose and resolve it efficiently. Ignoring this error can lead to interrupted browsing, preventing you from accessing important information or completing online tasks. Let’s dive into the details and get you back online!
Understanding the net::ERR_HTTP2_PROTOCOL_ERROR
The net::ERR_HTTP2_PROTOCOL_ERROR arises when there’s a violation of the HTTP/2 protocol specifications during communication between a web browser and a server. HTTP/2, designed to be faster and more efficient than its predecessor HTTP/1.1, introduces features like multiplexing (sending multiple requests over a single connection) and header compression. These advancements can sometimes lead to compatibility issues or misinterpretations, triggering the error. A common cause stems from inconsistencies in how a server implements HTTP/2 or how a browser interprets the server’s responses. These inconsistencies can manifest as malformed headers, incorrect stream management, or other protocol violations.
For example, if a server incorrectly compresses headers or if a browser encounters an unexpected stream identifier, the net::ERR_HTTP2_PROTOCOL_ERROR might surface. According to a study by Akamai, proper HTTP/2 implementation can reduce page load times by as much as 30% [Source: Akamai]. However, flawed implementations can negate these benefits and introduce errors like the one we’re discussing. Another potential cause is related to network infrastructure, such as proxy servers or firewalls that might not fully support HTTP/2 or might interfere with the communication. These intermediaries can sometimes corrupt or misinterpret HTTP/2 traffic, leading to the error.
Furthermore, browser extensions or plugins can also contribute to this problem. Some extensions might inject code that alters HTTP headers or interferes with the browser’s network requests, potentially causing HTTP/2 protocol violations. Keeping your browser and extensions updated is crucial, as updates often include bug fixes and improved compatibility with web standards. Regularly clearing your browser’s cache and cookies can also resolve issues caused by corrupted data. It’s a multifaceted issue, requiring a systematic approach to identify and address the underlying cause. Understanding the various potential sources of the net::ERR_HTTP2_PROTOCOL_ERROR is the first step toward resolving it.
Common Causes and Troubleshooting Steps
Several factors can trigger the net::ERR_HTTP2_PROTOCOL_ERROR, each requiring different troubleshooting approaches. Here’s a breakdown of common causes and practical solutions:
- Server-Side Issues: Misconfigured servers or faulty HTTP/2 implementations are frequent culprits.
- Browser Problems: Corrupted cache, outdated browser versions, or conflicting extensions can interfere with HTTP/2 communication.
- Network Interference: Proxy servers, firewalls, or even your internet service provider (ISP) might be the source of the problem.
Let’s explore specific troubleshooting steps:
- Clear Browser Cache and Cookies: This removes potentially corrupted data that might be causing the error. Go to your browser’s settings and find the option to clear browsing data.
- Disable Browser Extensions: Temporarily disable all extensions to see if one is causing the conflict. Re-enable them one by one to identify the problematic extension.
- Update Your Browser: Ensure you’re running the latest version of your browser. Updates often include bug fixes and improved compatibility with HTTP/2.
- Try a Different Browser: If the error persists, try accessing the website with a different browser. This helps determine if the issue is specific to your primary browser.
- Check Proxy Settings: If you’re using a proxy server, verify that it’s properly configured and supports HTTP/2.
- Flush DNS Cache: Flushing your DNS cache can resolve issues related to cached DNS records. On Windows, open Command Prompt and run ipconfig /flushdns. On macOS, use sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder.
For server-side issues, contacting the website’s administrator is often the best course of action. They can investigate server logs and configurations to identify and resolve any problems with their HTTP/2 implementation. If you’re a website owner, ensuring your server is properly configured for HTTP/2 is crucial. This involves verifying that your web server software (e.g., Apache, Nginx) is up-to-date and that the HTTP/2 module is enabled and correctly configured. According to Google’s Web Fundamentals documentation [Source: Google Developers], proper server configuration is essential for optimal HTTP/2 performance. Using online tools to test your server’s HTTP/2 support can also help identify potential issues.
Advanced Troubleshooting Techniques
If basic troubleshooting steps fail to resolve the net::ERR_HTTP2_PROTOCOL_ERROR, more advanced techniques might be necessary. These techniques often involve examining network traffic and server configurations in greater detail. One approach is to use browser developer tools to analyze HTTP/2 headers and identify any anomalies. Most modern browsers have built-in developer tools that allow you to inspect network requests and responses. By examining the HTTP/2 headers, you can look for malformed or unexpected values that might be triggering the error. This requires some understanding of the HTTP/2 protocol and its header structure.
Another useful technique is to use network monitoring tools like Wireshark to capture and analyze network traffic. Wireshark allows you to see the raw data being transmitted between your browser and the server, providing a detailed view of the HTTP/2 communication. This can help identify protocol violations or other issues that are not visible through browser developer tools. Analyzing Wireshark captures requires technical expertise and a solid understanding of networking protocols. However, it can be invaluable for diagnosing complex HTTP/2 problems. It allows you to see the exact data exchanged, including headers, payloads, and control frames, providing clues about the source of the error. For example, you might discover that the server is sending an invalid stream identifier or that the browser is not correctly handling flow control.
Furthermore, checking server logs can provide valuable insights into the cause of the error. Server logs often contain detailed information about HTTP requests and responses, including any errors or warnings that occurred during the processing of those requests. By examining the server logs, you might be able to identify specific requests that are triggering the net::ERR_HTTP2_PROTOCOL_ERROR. This can help you pinpoint the exact cause of the problem, such as a malformed request or a server-side bug. Server administrators can check error logs for specific messages related to HTTP/2 processing. These logs might reveal issues with header compression, stream management, or other protocol-related problems. Consulting the documentation for your web server software (e.g., Apache, Nginx) can provide guidance on interpreting server logs and troubleshooting HTTP/2 issues. This internal link will provide further information: troubleshooting network errors.
Preventing Future Occurrences
While resolving the net::ERR_HTTP2_PROTOCOL_ERROR is important, preventing its recurrence is even better. Proactive measures can minimize the chances of encountering this error in the future. One key strategy is to keep your browser and operating system up-to-date. Updates often include bug fixes and security patches that address known issues with HTTP/2 and other web technologies. Regularly updating your software ensures that you’re running the latest and most stable versions, reducing the likelihood of encountering compatibility problems.
Another important measure is to regularly clear your browser’s cache and cookies. Over time, cached data can become corrupted or outdated, leading to various browsing issues, including HTTP/2 errors. Clearing your cache and cookies periodically helps ensure that your browser is using fresh data, reducing the risk of encountering problems. In addition, be mindful of the browser extensions you install. Some extensions can interfere with HTTP/2 communication or introduce other conflicts. Only install extensions from trusted sources and regularly review your installed extensions to ensure they’re not causing any problems. Disabling unnecessary extensions can also improve your browser’s performance and stability.
Ensuring your network infrastructure is properly configured and supports HTTP/2 is also crucial. If you’re using a proxy server or firewall, verify that it’s compatible with HTTP/2 and that it’s not interfering with the communication between your browser and the server. Contacting your ISP to inquire about their HTTP/2 support can also be helpful. For website owners, regularly testing your server’s HTTP/2 implementation is essential. Use online tools to check for any configuration errors or compatibility issues. Monitoring server logs for HTTP/2-related errors can also help identify potential problems early on. Taking these proactive steps can significantly reduce the chances of encountering the net::ERR_HTTP2_PROTOCOL_ERROR in the future. The featured snippet paragraph is below:
The most direct cause of net::ERR_HTTP2_PROTOCOL_ERROR is a discrepancy in the HTTP/2 protocol communication between the browser and the web server. This usually manifests as the server sending data that the browser doesn’t expect or cannot understand, leading to a communication breakdown and the error message being displayed. Correct server configuration and regular updates are crucial to prevent this. [LSI keywords: HTTP/2, protocol error, browser, server, network].
- What exactly is HTTP/2?
- HTTP/2 is the second major version of the Hypertext Transfer Protocol, designed to be faster and more efficient than HTTP/1.1. It introduces features like multiplexing and header compression to improve web performance.
- Is net::ERR\_HTTP2\_PROTOCOL\_ERROR a security threat?
- While not directly a security threat, it can indicate misconfigurations that might be exploited. It's essential to address the error to ensure secure and reliable communication.
- Can a VPN cause this error?
- Yes, some VPNs might interfere with HTTP/2 communication, especially if they're not properly configured. Try disabling your VPN to see if it resolves the error.
Question & Answer :
I’m currently working on a website, which triggers a net::ERR_HTTP2_PROTOCOL_ERROR 200 error on Google Chrome. I’m not sure exactly what can provoke this error, I just noticed it pops out only when accessing the website in HTTPS. I can’t be 100% sure it is related, but it looks like it prevents JavaScript to be executed properly.
For instance, the following scenario happens :
- I’m accessing the website in HTTPS
- My Twitter feed integrated via https://publish.twitter.com isn’t loaded at all
- I can notice in the console the ERR_HTTP2_PROTOCOL_ERROR
- If I remove the code to load the Twitter feed, the error remains
- If I access the website in HTTP, the Twitter feed appears and the error disappears
Google Chrome is the only web browser triggering the error: it works well on both Edge and Firefox. (NB: I tried with Safari, and I have a similar kcferrordomaincfnetwork 303 error)
I was wondering if it could be related to the header returned by the server since there is this ‘200’ mention in the error, and a 404 / 500 page isn’t triggering anything.
Thing is the error isn’t documented at all. Google search gives me very few results. Moreover, I noticed it appears on very recent Google Chrome releases; the error doesn’t pop on v.64.X, but it does on v.75+ (regardless of the OS; I’m working on Mac tho).
Might be related to Website OK on Firefox but not on Safari (kCFErrorDomainCFNetwork error 303) neither Chrome (net::ERR_SPDY_PROTOCOL_ERROR)
Findings from further investigations are the following:
- error doesn’t pop on the exact same page if server returns 404 instead of 2XX
- error doesn’t pop on local with a HTTPS certificate
- error pops on a different server (both are OVH’s), which uses a different certificate
- error pops no matter what PHP version is used, from 5.6 to 7.3 (framework used : Cakephp 2.10)
As requested, below is the returned header for the failing ressource, which is the whole web page. Even if the error is triggering on each page having a HTTP header 200, those pages are always loading on client’s browser, but sometimes an element is missing (in my exemple, the external Twitter feed). Every other asset on the Network tab has a success return, except the whole document itself. 
Google Chrome header (with error):
Firefox header (without error):
A curl --head --http2 request in console returns the following success:
HTTP/2 200 date: Fri, 04 Oct 2019 08:04:51 GMT content-type: text/html; charset=UTF-8 content-length: 127089 set-cookie: SERVERID31396=2341116; path=/; max-age=900 server: Apache x-powered-by: PHP/7.2 set-cookie: xxxxx=0919c5563fc87d601ab99e2f85d4217d; expires=Fri, 04-Oct-2019 12:04:51 GMT; Max-Age=14400; path=/; secure; HttpOnly vary: Accept-Encoding
Trying to go deeper with the chrome://net-export/ and https://netlog-viewer.appspot.com tools is telling me the request ends with a RST_STREAM :
t=123354 [st=5170] HTTP2_SESSION_RECV_RST_STREAM --> error_code = "2 (INTERNAL_ERROR)" --> stream_id = 1
For what I read in this other post, “In HTTP/2, if the client wants to abort the request, it sends a RST_STREAM. When the server receives a RST_STREAM, it will stop sending DATA frames to the client, thereby stopping the response (or the download). The connection is still usable for other requests, and requests/responses that were concurrent with the one that has been aborted may continue to progress. […] It is possible that by the time the RST_STREAM travels from the client to the server, the whole content of the request is in transit and will arrive to the client, which will discard it. However, for large response contents, sending a RST_STREAM may have a good chance to arrive to the server before the whole response content is sent, and therefore will save bandwidth.”
The described behavior is the same as the one I can observe. But that would mean the browser is the culprit, and then I wouldn’t understand why it happens on two identical pages with one having a 200 header and the other a 404 (same goes if I disable JS).
In my case it was - no disk space left on the web server.
