aspire app giving 431 error

Question

aspire app giving 431 error

Ghongde,Shivanand 0

I am getting a 431 error in aspire, but it is working for other my team members. for the newly created aspire app, I am getting the same error. I cleaned the solution cleaned the cookies and all but still nothing worked.

AgaveJoe 30,226 Reputation points

2025-09-11T22:26:51.1966667+00:00

The 413 HTTP status code means "Payload Too Large". Since it's a 4xx error, the issue is on the client side, meaning the request you're sending is too large for the server to accept. This can be caused by:

A very large file upload.

Excessive data being sent in the request body (e.g., in an API call).

A large cookie or too many cookies in the request headers.

To resolve this, you need to compare the size of the payload you are sending with the maximum payload size your server is configured to handle.
Ghongde,Shivanand 0 Reputation points

2025-09-11T22:40:29.5166667+00:00

I am experiencing an HTTP 431 error in Aspire, which seems to be specific to my environment. Interestingly, the application is working fine for my other team members.

To investigate, I created a new demo project in Aspire to test whether the issue is isolated to the existing project or my setup. However, even in the newly created demo project, I am encountering the same 431 error.

I have already attempted the usual troubleshooting steps, including cleaning the solution, clearing cookies, and restarting the environment, but none of these measures resolved the issue.

For context, the existing project (Sistine) is functioning properly for my teammates, which suggests that the problem is specific to my system or environment rather than the application itself.
Ghongde,Shivanand 0 Reputation points

2025-09-12T04:41:42.55+00:00

Since this issue seems to be isolated to my environment, would it be possible to schedule a short Teams call? I can share my screen to demonstrate the 431 error and we can troubleshoot it together.

1 answer

Your answer

AgaveJoe 30,226 Reputation points

2025-09-11T22:26:51.1966667+00:00

The 413 HTTP status code means "Payload Too Large". Since it's a 4xx error, the issue is on the client side, meaning the request you're sending is too large for the server to accept. This can be caused by:

A very large file upload.

Excessive data being sent in the request body (e.g., in an API call).

A large cookie or too many cookies in the request headers.

To resolve this, you need to compare the size of the payload you are sending with the maximum payload size your server is configured to handle.
Ghongde,Shivanand 0 Reputation points

2025-09-11T22:40:29.5166667+00:00

I am experiencing an HTTP 431 error in Aspire, which seems to be specific to my environment. Interestingly, the application is working fine for my other team members.

To investigate, I created a new demo project in Aspire to test whether the issue is isolated to the existing project or my setup. However, even in the newly created demo project, I am encountering the same 431 error.

I have already attempted the usual troubleshooting steps, including cleaning the solution, clearing cookies, and restarting the environment, but none of these measures resolved the issue.

For context, the existing project (Sistine) is functioning properly for my teammates, which suggests that the problem is specific to my system or environment rather than the application itself.
Ghongde,Shivanand 0 Reputation points

2025-09-12T04:41:42.55+00:00

Since this issue seems to be isolated to my environment, would it be possible to schedule a short Teams call? I can share my screen to demonstrate the 431 error and we can troubleshoot it together.

Answer 1

Thank you for reaching out.

A 431 — Request Header Fields Too Large means the server refused your request because something in the request headers exceeded what the server will accept. That usually means either one header (for example an oversized Authorization token or a very long Referer) or the combined size of many headers (often a very large cookie string) is too big.
Because your teammates don’t see the error but you do, it strongly suggests the extra/oversized header is coming from your machine or browser (cookies, auth tokens, an enterprise proxy, or a local tool like Fiddler) rather than from the Aspire app itself.

Troubleshooting

1. Incognito / Private Window (Quick Diagnostic)

Open the app in a private window. If it works there, that proves the problem is browser-stored data (cookies/localStorage). This is the fastest way to narrow the cause.

2. Clear All Site Data for the Origin (Not Just Obvious Cookies)

In DevTools → Application (or Storage): use Clear site data for (or your Aspire origin). Remove Cookies, Local Storage, Session Storage, IndexedDB — and specifically delete cookies named like .AspNetCore.Cookies or .AspNetCore.Identity.Application if present. Then fully restart the browser. Many people think “I cleared cookies” but miss origin-scoped storage or session stores.

3. Inspect the Actual Request Headers (Diagnostic, Critical)

Use DevTools Network tab (or Fiddler/Postman) to capture the failing request. Look at the raw Request Headers: the Cookie header, Authorization, Referer, or any custom headers — note their sizes. This tells you the exact offender instead of guessing.

4. Check System-Level / Corporate Tools

If clearing browser data didn’t help, check whether a corporate proxy, VPN, SSO agent, or a system-wide tool like Fiddler is appending headers or injecting tokens. These can affect only your machine and cause 431. Temporarily disable them and retry.

5. Re-authenticate External Identity Tools

Sign out and sign back into Visual Studio, Azure SSO, or any other system that may cache tokens outside the browser. Corrupted or oversized SSO tokens can live outside normal browser cookies.

6. Reset Local Dev Host State (If Needed)

If you suspect local host config corruption (IIS Express / VS debug host), recreate the environment state: close dev tools, remove per-solution caches (they’ll be rebuilt). This is less common but occasionally helpful.

Workarounds

Temporary Dev Unblock: You can temporarily allow larger headers on your local dev server so you’re not blocked while you investigate. This is a workaround only — it gets you running but doesn’t fix the root cause and should not be used in production.
Short-Term Fix for Uploads/Referers: If a specific feature sends a very long referer or huge metadata, try sending smaller payloads or split large requests while you diagnose the header issue.

Summary

Try Incognito — does it work? If yes → clear site data for the origin and restart browser.
If not, capture the failing request in DevTools or Fiddler and identify which header is huge.
If the header is coming from a system tool or SSO, disable/re-auth and retry.
Only if you remain blocked and need a temporary unblock, use the local dev server workaround (increase header limits) while continuing to find the real cause.

Helpful References

Here are the Microsoft Learn links related to the HTTP 431 Request Header Fields Too

Let me know if you need any further help with this. We'll be happy to assist.

If you find this helpful, please mark this as answered.

Ghongde,Shivanand 0 Reputation points

2025-09-12T08:53:47.1233333+00:00

Thank you for sharing these detailed troubleshooting steps. I’ve gone through all of the approaches you mentioned, but I’m still facing the same 431 error. As I mentioned earlier, my teammates are able to run the application without any issues, so I’m not sure why it’s only affecting me. Could we please connect over Teams to investigate this further and try to identify the root cause?
Deleted

This comment has been deleted due to a violation of our Code of Conduct. The comment was manually reported or identified through automated detection before action was taken. Please refer to our Code of Conduct for more information.

Share via

aspire app giving 431 error

1 answer

Your answer