We’ve all been there—everything looks perfect, but your API request still fails. 😭 You check your code a hundred times, but the response stubbornly refuses to cooperate. Been there, done that! Let’s break down some common reasons why your API request might be failing and how to fix them.

1. CORS Errors – The Browser Gatekeeper

You hit an API, and BOOM—CORS error. The browser yells something about "Access-Control-Allow-Origin."

Why does this happen?
Browsers block requests to a different domain unless the server explicitly allows it.

How to fix it?

  • If you own the backend, enable CORS using middleware like cors in Express or decorators in NestJS.
  • If it’s a third-party API, check if they provide a proxy or a server-side workaround (or beg them nicely to enable CORS 😆).

2. 401 Unauthorized – Who Are You Again? 🤔

You send a request, and the server basically replies, "I don’t know you."

Why does this happen?

  • Missing or incorrect authentication headers.
  • Expired tokens.

How to fix it?

  • Double-check your API key, token, or credentials.
  • If using JWTs, make sure they are still valid and haven’t expired.
  • Some APIs require sending tokens as Bearer —watch out for formatting!

3. 404 Not Found – Did You Check the Address?

You request data, but the server responds with: "What are you looking for?"

Why does this happen?

  • The API endpoint is incorrect (/users vs /user 🤦‍♂️).
  • The resource doesn’t exist.

How to fix it?

  • Double-check the API URL and make sure you’re using the correct route.
  • If using dynamic IDs, make sure the requested data actually exists in the database.

4. 500 Internal Server Error – The Server is Crying 😭

You did everything right, but the server throws a 500 error.

Why does this happen?

  • Something is broken on the server (not your fault… probably 😆).
  • The server tried processing your request but failed.

How to fix it?

  • If you own the backend, check server logs (console.log is your best friend).
  • If it’s a third-party API, try again later—it might be down.

Final Thoughts 💡
Debugging API failures is frustrating, but once you understand why they happen, fixing them gets easier! Now, go forth and send those requests with confidence.

Have you ever spent hours debugging an API issue, only to realize it was a tiny typo? Share your story in the comments! 😆