What's the best way to debug an API that returns a 401 error?

If you are a web developer, you probably have encountered a 401 error when trying to access an API or a web service. This error means that you are not authorized to access the resource, and it can be frustrating and confusing to debug. In this article, we will show you some common causes and solutions for a 401 error, and how to use tools and techniques to troubleshoot it effectively.

1 Check your credentials

The first thing you should do when you get a 401 error is to check your credentials. Make sure that you are using the correct API key, token, username, password, or any other authentication method that the API requires. Sometimes, the credentials may expire, change, or be revoked, so you need to update them accordingly. Also, check if the API has any specific rules or formats for the credentials, such as headers, parameters, or encryption.

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Ali Samir

Frontend Engineer @Taager
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Debugging a 401 Unauthorized error: - Ensure the Authorization header is correct. If using tokens, validate their integrity and expiry. - Double-check API keys or credentials. Avoid typos or extraneous spaces. - Confirm you're accessing the right endpoint with correct authentication requirements. - Refer to API documentation for authentication specifics. - Verify if you've hit request limits. Some APIs might return 401 instead of 429. - Inspect server logs for more details on the denial. - Use Postman or cURL for testing the request independently. - If over HTTPS, check SSL configurations. Always manage and store credentials with caution.

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Bekjon Ibragimov

Full Stack Developer | 5+YOE | GO | .NET | React.js | Ex Agoda Software Engineer
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Make sure to check if required cookies or authentication tokens are appended to request headers. Also, make sure that cookies aren't being disregarded, this may happen if, for example, the server tries to assign cookies over insecure connection (http)

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2 Check your permissions

The next thing you should do is to check your permissions. Some APIs may have different levels of access or scopes for different resources, endpoints, or methods. You need to make sure that you have the right permission to perform the action that you want. For example, you may be able to read data from an API, but not write or delete it. You can usually find the permission information in the API documentation or by contacting the API provider.

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Akansh Mahendra

Team Lead @ Nagarro | Web Development
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To debug a 401 error in an API: - Check request authorization credentials. - Review API docs for requirements. - Verify token or credentials validity. - Inspect request details (headers, params). - Use authentication libraries if available. - Look for typos and case sensitivity. - Check response headers and error messages. - Test with tools like Postman or curl. - Contact API support if needed. - Check server logs for insights. - Monitor rate limits. - Address CAPTCHA or 2FA if required. These steps help identify and resolve the issue causing the 401 error efficiently.

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3 Check your request

Another possible cause of a 401 error is a malformed or invalid request. You need to check your request method, URL, headers, body, and parameters, and make sure that they match the API specifications and expectations. Sometimes, a typo, a missing slash, a wrong content type, or a wrong parameter name can trigger a 401 error. You can use tools like Postman, Curl, or Insomnia to test and inspect your requests and compare them with the API examples.

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Tomas Henkenhaf

Cadet-in-Training at Toronto Police Service
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Details matter in APIs. Ensuring that every part of your request aligns with expected standards is critical, as even a minor misstep can be a barrier between you and a successful API call.

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4 Check your logs

If none of the above steps solve your problem, you may need to check your logs. Logs are records of the events and activities that happen in your application or system. They can help you identify and debug errors, issues, or anomalies. You can use tools like Loggly, Splunk, or ELK to collect, analyze, and monitor your logs. You can also use tools like Sentry, Bugsnag, or Rollbar to capture and report errors and exceptions in your code.

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5 Check your network

The last thing you should do is to check your network. Sometimes, a 401 error may be caused by a network issue, such as a firewall, a proxy, a VPN, or a CORS policy. You need to make sure that your network allows and supports the communication between your application and the API. You can use tools like Ping, Traceroute, or Wireshark to test and diagnose your network connectivity and performance.

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6 Learn more

Debugging an API that returns a 401 error can be difficult, but not impossible. To help with the process, there are several steps and tools that can be used to identify and fix the source of the problem, enabling you to access the API successfully. If you are interested in learning more about debugging APIs and web services, you can explore resources such as How to Debug REST APIs, Debugging Web Services with SoapUI, and Debugging and Testing GraphQL APIs.

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7 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?

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What's the best way to debug an API that returns a 401 error?

1

2

3

4

5

6

7

1 Check your credentials

2 Check your permissions

3 Check your request

4 Check your logs

5 Check your network

6 Learn more

7 Here’s what else to consider

Web Development

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What's the best way to debug an API that returns a 401 error?

1

2

3

4

5

6

7

1 Check your credentials

2 Check your permissions

3 Check your request

4 Check your logs

5 Check your network

6 Learn more

7 Here’s what else to consider

Web Development

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