Detecting HTTP Exception Errors in Web

What is HttpExceptionError in Web apps?

HTTPExceptionError captures unexpected, fatal exceptions thrown during the HTTP request lifecycle on the client side, before a valid HTTP status code is even received from the server.

Why it matters

Unlike status code errors, exceptions often cause the underlying JavaScript Promise to reject unexpectedly. If unhandled, this can crash the entire React/Angular component tree, resulting in a blank white screen for the user.

Why does this happen?

CORS (Cross-Origin Resource Sharing) Failures

If the backend does not return the correct Access-Control-Allow-Origin headers, the browser will block the response for security reasons, throwing a CORS exception in the client code.

Network Disconnections

If the user loses internet connectivity (e.g., entering a tunnel) precisely while a fetch request is pending, the browser will throw a network error exception.

JSON Parsing Failures

If the backend promises an application/json response but accidentally returns an HTML error page (e.g., from an Nginx gateway timeout), calling response.json() will throw a syntax error in the browser.

How to fix it using Appxiom

• Analyze stack trace: Appxiom provides the exact minified and source-mapped stack trace pointing directly to the line of JavaScript/TypeScript code that triggered the issue.
• Trace activity trail: The activity trail provides a chronological list of user interactions (clicks, route changes) and network calls that occurred right before the issue, helping developers reproduce the exact user journey.