Error 406 unacceptable

Errors & Troubleshooting | Updated 2026

A 406 "Not Acceptable" error means the server understood your request but the response it would generate is not acceptable according to the request headers. On shared hosting, this error is almost always caused by ModSecurity (the web application firewall) blocking a request it considers suspicious.

In This Guide

What Causes a 406 Error
ModSecurity False Positives
.htaccess Causes
How to Fix It

Most Common Cause

ModSecurity is blocking your request

On Ultra Web Hosting servers, the 406 error is typically triggered by ModSecurity detecting something in your form submission, URL, or request that matches a security rule. This is a false positive when it happens on your own website. Open a support ticket with the URL and what you were doing, and we can add an exception for your account.

01. What Causes a 406 Error

The HTTP 406 status code technically means "Not Acceptable" in terms of content negotiation (the client asked for a content type the server cannot provide). However, on web hosting servers with ModSecurity enabled, the 406 code is commonly returned when the firewall blocks a request.

Common triggers:

Form submissions - Posting content that contains HTML tags, JavaScript, SQL-like syntax, or other patterns that look like an attack to the firewall
URL parameters - Query strings that contain characters or patterns matching injection rules
WordPress editor - Saving posts or pages with HTML, shortcodes, or embedded code
File uploads - Uploading files with names or content that trigger a rule

02. ModSecurity False Positives

ModSecurity protects your website from SQL injection, cross-site scripting (XSS), and other attacks by inspecting incoming requests. Sometimes, legitimate content triggers a rule. For example, if you are writing a blog post about SQL and include example SQL code, ModSecurity might flag it as an actual SQL injection attempt.

This is a false positive. The content is legitimate, but the firewall cannot tell the difference between example code in a blog post and an actual attack.

03. .htaccess Causes

Less commonly, a 406 error can be caused by content negotiation rules in your .htaccess file. If you have rules that use Options +MultiViews or custom AddType directives, they can cause the server to reject requests for content types it cannot serve.

Try temporarily renaming your .htaccess file to test. If the 406 goes away, the issue is in your .htaccess.

04. How to Fix It

For ModSecurity blocks (most common)

Open a support ticket and include:

The exact URL where the error occurs
What you were doing (submitting a form, saving a post, uploading a file)
The approximate time the error happened

We will check the ModSecurity audit log, identify the rule that triggered, and add an exception for your account if it is a false positive.

For .htaccess issues

Rename .htaccess temporarily to .htaccess.bak using File Manager
Test your site - If the 406 is gone, the issue is in .htaccess
Review the file for MultiViews, AddType, or other content negotiation directives
Remove or fix the problematic directive
Rename the file back to .htaccess

See Complete Guide to .htaccess for more on .htaccess troubleshooting.

Getting 406 Errors?

Open a ticket with the URL and time of the error. We will identify the trigger and fix it for you.

Open a Support Ticket

Quick Recap

406 errors on shared hosting are usually ModSecurity - Not content negotiation
Common triggers - Form submissions with HTML, code examples, SQL-like content
Open a support ticket - We can add exceptions for false positives
Check .htaccess - MultiViews or AddType directives can also cause it
Include the URL and time when reporting so we can find the exact rule

Error troubleshooting guide · Last updated March 2026 · Browse all Error articles