HTTP troubleshooting
400 Bad Request
Your uptime monitor detected that the server could not understand or process the request because of an error on the client side. This usually means the data sent by the monitor or browser was corrupted, malformed, or broke the server's rules.
What 400 Status Code Means
- 1.
Malformed request syntax
The data package sent to the server was scrambled, incomplete, or used a format the server does not allow.
- 2.
Invalid request routing
The request tried to use a bad routing path, an illegal character in the URL, or a header that is too large for the server to read.
- 3.
Uptime monitor behavior
Our monitor flagged this because the server completely rejected the connection attempt instead of loading the page normally.
Troubleshooting checklist
- 1.
Inspect the request URL
Look closely at the web address for any typos, spaces, or weird special characters that shouldn't be there.
- 2.
Check custom headers
Review any special user-agents, tokens, or custom headers you added to this monitor to ensure they are formatted right.
- 3.
Review payload data
If your monitor sends POST or PUT data, double-check that the JSON, XML, or form text is perfectly written.
- 4.
Examine server logs
Check your web server error logs to see exactly why it rejected the incoming request data.
How to Fix It
- 1.
Fix URL spelling errors
Clean up the web address in your monitor dashboard and remove any invalid spaces or symbols.
- 2.
Correct data formatting
Fix any broken syntax or missing brackets in the payload data configuration of your uptime monitor.
- 3.
Clear cookies and cache
If testing manually, clear your browser cookies since old or bad cookies can trigger a 400 error on that specific site.
- 4.
Adjust server size limits
Increase the allowable header size limits in your NGINX or Apache server setup if your monitor uses large security tokens.
After the Service is Fixed
- 1.
Verify with Uptime Monitor
Confirm that the monitor now gets a happy 200 OK status after you fix the broken request settings.
- 2.
Test with standard tools
Use a tool like cURL or Postman to send the exact same request and make sure it passes safely.
- 3.
Monitor input channels
Keep an eye on your API endpoints to ensure they handle slightly messy data without completely crashing.
- 4.
Log validation drops
Set up an alert system to tell you if the server suddenly starts rejecting a large number of client requests.