This article describes steps to resolve Nginx 400 Bad Request Header or Cookies error.
I run some of my websites via Nginx HTTP servers, and some of my Nginx configurations are configured for different environments. So, when I got this error message (400 Bad Request: Request Header or Cookie Too Large) while working on one of my servers, I quickly researched and resolved it.
If you are in a similar situation, follow the steps below to resolve it quickly.
Oh, by the way, this could also be your browser is sending a very large cookie, and the server is refusing to serve the page. In addition to a browser sending large cookies, it could also be an Nginx configuration issue, and adjusting Nginx’s buffer size to accommodate large cookies could help.
If you don’t want to clear or reset your browser cookies, follow the steps below to adjust the Nginx configuration to allow large cookies.
When you see this error message, it means a header or some of the headers sent to Nginx is too large and well over the configuration limit, and Nginx is rejecting it. To get it resolved, follow the steps below:
Oh, so you know, Nginx’s default buffer number and size are 4 and 8k.
So you’ll get that error message if a header size is above the limit above.
Next, on the Nginx HTTP server, open the server configuration file.
sudo nano /etc/nginx/sites-available/example.com.conf
The location of your server configuration file may differ from the above. When the file opens, add this line of configuration and save.
server {
# .
large_client_header_buffers 4 16k;
# .
}
Save the file and exit.
The Nginx states that the line is only valid in HTTP or server contexts. So make sure you add the configuration line or context. After that, restart or reload the Nginx server.
sudo systemctl reload nginx.service
Test again, and the error should be gone.
If you still get the error after restarting, bump the number to 4 and 32k. Then restart the Nginx server.
Another thing to look at is if you’re running an Nginx proxy with proxy_set_header config, you should remove that line from your proxy configuration block.
For example, remove the line below from your proxy configuration block if you have it configured, then save and restart Nginx.
proxy_set_header Host app.example.com;
These steps above should get you back to a functioning site.
If all the steps above don’t work, other issues may be in play there. First, please clear your browser’s cookies and maybe reset it bythemeleting all stored data. Then, hopefully, it should work.
Why remove proxy_set_header Host? Don’t just remove stuff you don’t understand?
Request Header Or Cookie Too Large
VERY NICE
am sorry but please stop showing that
Very good
Why it is no working
why remove proxy_set_header Host ?
some sites will stop working
SMH
horrible idea to remove the Host header, you probably saw that here https://stackoverflow.com/questions/17524396/400-bad-request-request-header-or-cookie-too-large and thought it was a good idea for some reason. you’re also suggesting to “bump 4 to 32k” but that’s also incorrect if you go over syntax, it should be doubling 16k to 32k not bumping the number of buffers.. avoid the changes suggested here, go read over the docs instead.