---
title: "ERR_HTTP2_PROTOCOL_ERROR — test your site, then fix it"
description: "Run a free live check to see whether ERR_HTTP2_PROTOCOL_ERROR is happening on your own domain right now, then work through the causes ranked most likely…"
canonical: "https://lemwatch.com/errors/err-http2-protocol-error"
source: "https://lemwatch.com"
---

# ERR_HTTP2_PROTOCOL_ERROR: The HTTP/2 stream failed

> The browser ended an HTTP/2 stream after detecting a protocol problem. Large response headers and incompatible HTTP/2 handling at an origin, CDN, proxy or WAF are common leads, but the failing hop needs to be identified before changing configuration.

## Short answer

 The browser ended an HTTP/2 stream after detecting a protocol problem. Large response headers and incompatible HTTP/2 handling at an origin, CDN, proxy or WAF are common leads, but the failing hop needs to be identified before changing configuration.

## What ERR_HTTP2_PROTOCOL_ERROR means

 HTTP/2 multiplexes several streams over one connection and has strict framing and header rules. When a peer detects a violation, the browser can reset the affected stream or connection; the page may therefore fail without an HTTP status the browser can show.

## Causes and fixes, most likely first

- Response headers exceed a header-size limit at the origin or an intermediary. Compare the response headers on a working and failing request. Reduce oversized cookies or duplicated headers where possible, then align the documented header limits across the origin, CDN, proxy and WAF.
- A proxy or WAF between the browser and origin has a buggy HTTP/2 implementation. Reproduce from the same network and compare a controlled HTTP/1.1 request with HTTP/2. If only HTTP/2 fails, collect the request ID and edge/origin logs before updating or temporarily disabling HTTP/2 on the confirmed hop.

## How to stop it happening again

- Review response-header growth and test representative routes over HTTP/1.1 and HTTP/2 after changing a CDN, proxy, WAF or session-cookie policy.

## Check your own domain

 A public probe can show whether a request completes from one external vantage point. It cannot prove which protocol hop failed or reproduce browser- and network-specific behaviour on its own.

## Frequently asked questions

### Should I just disable HTTP/2?

 Use that only as a short diagnostic or mitigation. A successful HTTP/1.1 request narrows the investigation; it does not by itself identify the failing service. Fix the confirmed header or intermediary issue before deciding whether HTTP/2 should remain disabled.



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- Source: https://lemwatch.com/pricing (facts verified from the product's own plan limits).



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- [Lemwatch pricing](https://lemwatch.com/pricing)