How to Fix a 431 Request Header Fields Too Large Error on Your Website

A 431 Request Header Fields Too Large error means your browser sent an HTTP request with headers, usually cookies, that were too large for the server to process. The server rejects the request before your page loads, so you see a blank error screen instead of your website.

This error almost always comes from something stored in your browser for that specific website, not from a problem with your hosting account. It is also one of the easier errors to fix yourself.

Check Whether It's Just You or Every Visitor

Before changing anything, confirm the scope of the problem.

• Open the website in a different browser or an incognito/private window. If it loads fine there, the issue is tied to cookies stored in your regular browser for that site.
• Ask someone else to load the same page. If it works for them but not you, the cause is local to your browser, not the server.

If the error appears for every visitor in every browser, the cause is more likely a misbehaving plugin or script on the website itself rather than a visitor's cookies. See the WordPress section below.

Clear Cookies for the Site

This fixes the error in most cases.

1. Open your browser's site settings for the affected domain. In Chrome, click the padlock icon next to the address bar and choose Cookies and site data.
2. Delete all cookies stored for that domain.
3. Close and reopen the browser, then visit the website again.

You do not need to clear your entire browsing history. Clearing cookies for just the one affected domain is enough.

If the Website Runs on WordPress

WordPress sites build up large cookies over time, especially with plugins that track sessions, run A/B tests, or load several analytics tools at once. This is the most common cause of a 431 error that affects every visitor, not just one person.

1. Log out of the WordPress admin area completely, clear your browser cookies for the site, then log back in.
2. If you cannot reach wp-admin at all because the error blocks it too, open File Manager and rename the plugins folder inside wp-content. This deactivates every plugin at once so you can log in again.
3. Once logged in, reactivate plugins one at a time, reloading the site after each one, until you find the plugin causing the oversized cookie.
4. Remove or replace that plugin, particularly if it is a session manager, a caching plugin with broken cookie handling, or a tool that stacks several tracking cookies at once.

Resetting your WordPress admin password also clears your old login cookie, which helps when a corrupted session is the root cause.

If Clearing Cookies Doesn't Help

If the error keeps coming back after clearing cookies and checking plugins, the header size limit allowed by the server itself may need adjusting. This is a server-level setting you cannot change yourself from cPanel or DirectAdmin, so contact ZIPROF support with the exact URL where the error appears and they can check and adjust it on the server side.

For a related issue, see How to Fix a 413 Request Entity Too Large Error on Your Website, which deals with oversized uploads rather than oversized headers.