# REST API Troubleshooting

In this section, you will find:

* Examples of errors you might get while making requests to YouTrack REST API.

* Suggestions how to update these requests and fix the errors.

Here is the list of topics in this section:

- [400 Bad Request When Adding a Custom Field Value to a Set](api-troubleshoot-incorrect-request-url.html)
- [400 Bad Request When Creating a User](api-troubleshoot-create-user-endpoint.html)
- [400 Bad Request When Project ID Is Numeric](api-troubleshoot-numeric-project-id.html)
- [400 Bad Request When Creating an Issue Without Required Field Value](api-troubleshoot-missing-type.html)
- [400 Bad Request When Updating a Conditional Field](api-troubleshoot-updating-conditional-field.html)
- [400 Bad Request When Using a Ring ID](api-troubleshoot-ring-id.html)
- [400 Bad Request When Uploading an Attachment](api-troubleshoot-attachment-boundary.html)
- [404 Not Found Caused by an Incorrect Request URL](api-troubleshoot-incorrect-issue-url.html)
- [500 Server Error When Updating a Custom Field](api-troubleshoot-incorrect-field-type.html)
- [500 Server Error When Adding a Field to a Project](api-troubleshoot-custom-field-prototype.html)