Reload with Ctrl+Shift+R, then try Incognito. If that works, clear cached files and disable extensions. Also pause antivirus HTTPS scanning. If every browser and device fails on that site, the website's server or CDN is sending broken HTTP/2 responses.

What ERR_HTTP2_PROTOCOL_ERROR actually means

Modern sites use HTTP/2, which sends many files over a single connection in small frames. ERR_HTTP2_PROTOCOL_ERROR appears when Chrome receives a frame that breaks the protocol rules: a malformed header, an unexpected reset, or a response cut short.

On the visitor side, antivirus that inspects HTTPS and corrupted cache data are common triggers. On the server side, typical causes are oversized or invalid response headers, a proxy or CDN timing out mid-stream, a full disk, or a bug in a web-server module.

How it shows up

  • “This site can’t be reached. The webpage might be temporarily down or it may have moved permanently. ERR_HTTP2_PROTOCOL_ERROR”.
  • A page partially loads, or downloads and uploads fail midway.
  • The site works in Firefox but not in Chrome or Edge (or the reverse).

What causes ERR_HTTP2_PROTOCOL_ERROR

  • Corrupted cached files or cookies for the site.
  • Antivirus or a proxy re-encrypting HTTPS traffic.
  • Browser extensions modifying requests.
  • Server/CDN issues: invalid headers, response size limits, proxy timeouts or a full server disk.

How to fix it, step by step

  1. Hard refresh and IncognitoPress Ctrl+Shift+R (Mac: Cmd+Shift+R), then open the site in an Incognito window.
  2. Clear site dataClick the icon left of the address bar → Site settings → Delete data, or clear all cached images and files at chrome://settings/clearBrowserData.
  3. Disable extensionsTurn off extensions at chrome://extensions and reload. Re-enable them one at a time to find the cause.
  4. Pause HTTPS scanningSwitch off web/HTTPS scanning in third-party antivirus temporarily. If the site loads, add an exception.
  5. Update ChromeOpen chrome://settings/help to install the latest version and relaunch.
  6. Site owners: check the serverLook at the web server and CDN error logs at the time of failure. Check for very large cookies or headers, proxy buffer limits, timeouts on long requests, and free disk space.
How to tell it worked: The page and its images and downloads load completely in a normal Chrome window.

Keeping it from coming back

Keep Chrome and security software updated. Site owners should keep server software patched and monitor header sizes and disk space.