---
title: "Introduction"
url: https://docs.catalyst.zoho.com/en/cloud-scale/help/authentication/whitelisting/custom-user-validation/introduction/
description: "Custom User Validation allows you to validate user sign ups using custom logic"
last_updated: 2026-08-28T06:26:16Z
service: Cloud Scale
type: general
---

# Custom User Validation

Catalyst offers you the option to validate and authorize end-users to your application using custom functions. This option allows you to configure a [Catalyst Basic I/O function](https://docs.catalyst.zoho.com/en/serverless/help/functions/basic-io) to contain the logic of the manner you wish to authorize the user with. During user sign up, the credentials of the user will be validated through this Basic I/O function. 

> **Note:** To enable **Custom User Validation**, you must first ensure that [Public Signup](https://docs.catalyst.zoho.com/en/cloud-scale/help/authentication/public-signup/) has been enabled.

Refer the code snippets below a sample Custom User Validation function in Java, Node.js, and Python:

**Java**

**Custom User Validation - Java**

```java
public class MainClass implements ZCFunction {
    private static final Logger LOGGER = Logger.getLogger(MainClass.class.getName());
    @Override
    public void runner(Context context, BasicIO basicIO) throws Exception {
        try {
            ZCProject.initProject();
            ZCSignupUserValidationRequest requestDetails = ZCSignupUserService.getSignupValidationRequest(basicIO);
            if (requestDetails != null) {
                /*Validation logic starts */
                LOGGER.info("Inside null check");
                ZCSignupUserValidationResponse validationResponse = ZCSignupUserValidationResponse.getInstance();
                if (requestDetails.getUserDetails().getEmailId().contains("@notallowedmail")) {
                    validationResponse.setStatus(ZCSignupValidationStatus.FAILURE); // The user has failed authentication
                } else {
                    validationResponse.setStatus(ZCSignupValidationStatus.SUCCESS); // The actions that occur in the event of a successful authentication can be customized
                    ZCSignupResponseUserDetails respUserDetails = ZCSignupResponseUserDetails.getInstance();
                    respUserDetails.setFirstName("{customFirstName}");
                    respUserDetails.setLastName("{customLastname}");
                    respUserDetails.setRoleIdentifier("{customRoleName}");
                    respUserDetails.setOrgId("{customOrgId}");
                    validationResponse.setUserDetails(respUserDetails);
                }
                basicIO.write(validationResponse);
                /* Validation logic ends*/
            }
        } catch (Exception e) {
            basicIO.write(e);
            LOGGER.log(Level.SEVERE, "Exception in MainClass", e);
            basicIO.setStatus(500);
        }
    }
}

```

**Node.js**

**Custom User Validation - Node.js**

```javascript
const catalyst = require("zcatalyst-sdk-node");
module.exports = (context, basicIO) => {
  const catalystApp = catalyst.initialize(context);
  const userManagement = catalystApp.userManagement();
  const requestDetails = userManagement.getSignupValidationRequest(basicIO);
  if (requestDetails !== undefined) {
    if (requestDetails.user_details.email_id.includes("node")) {
      basicIO.write(
        JSON.stringify({
          status: "failure",
        })
      );
    } else {
      basicIO.write(
        JSON.stringify({
          status: "success",
          user_details: {
            first_name: "CustomFirstName",
            last_name: "CustomLastName",
            role_identifier: "CustomRole",
            org_id: "CustomOrgID", //If you are providing the Org ID, make sure it is copied exactly from the console.
          },
        })
      );
    }
  }
  context.close();
};

```

**Python**

**Custom User Validation - Python**

```python
import json
import zcatalyst_sdk

def handler(context, basicio):
    app = zcatalyst_sdk.initialize()
    auth_service = app.authentication()
    request_details = auth_service.get_signup_validation_request(basicio)
    if request_details:
        if "spam.com" in request_details["user_details"]["email_id"]:
            basicio.write(json.dumps({"status": "failure"}))
        else:
            basicio.write(
                json.dumps(
                    {
                        "status": "success",
                        "user_details": {
                            "first_name": "Amelia",
                            "last_name": "Jack",
                            "role_identifier": "cx_role",
                            "org_id": orgId,  # If you are providing the Org ID, make sure it is copied exactly from the console.
                        },
                    }
                )
            )
    context.close()

```

> **Note:** These snippets are also available in the Catalyst [Java SDK](https://docs.catalyst.zoho.com/en/sdk/java/v1/cloud-scale/authentication/custom-user-validation/), [Node.js SDK](https://docs.catalyst.zoho.com/en/sdk/nodejs/v2/cloud-scale/authentication/custom-user-validation/), and [Python SDK](https://docs.catalyst.zoho.com/en/sdk/python/v1/cloud-scale/authentication/custom-user-validation/) repositories.