---
title: Error Handling & Validation
description: Review and fix import errors directly in the UI before confirming.
---

import { VimeoEmbed } from '/snippets/vimeo-embed.mdx';

## Pre-Import Validation

After uploading your file and mapping fields, Twenty validates your data **before** importing. This allows you to catch and fix errors without affecting your existing data.

## How It Works

1. **Upload** your CSV file
2. **Map** your columns to Twenty fields
3. **Review** the potential errors highlighted in yellow
4. **Fix errors** directly in the UI
5. **Confirm** the import

<VimeoEmbed videoId="1145273857" title="Video demonstration" />

## Error Display

Rows with issues are highlighted in **yellow**. You can:

* **Edit the cell directly** to fix the error
* **Remove the row** to skip it entirely

This inline editing saves time—no need to go back to your spreadsheet, fix errors, and re-upload.

## Common Error Types

### Duplicate Values

**Cause**: A unique field (email, domain) already exists in Twenty or appears twice in your file.

**Fix**:

* Edit the duplicate value in the import UI
* Remove one of the duplicate rows

See [Uniqueness Constraints](/l/zh/user-guide/data-migration/capabilities/uniqueness-constraints) for more details on how uniqueness is enforced.

### Invalid Format

**Cause**: Data doesn't match the expected format (e.g., invalid email, wrong date format).

**Fix**: Edit the cell to use the correct format.

See [Field Mapping](/l/zh/user-guide/data-migration/capabilities/field-mapping) for the expected format of each field type.

### Missing Required Fields

**Cause**: A required field is empty.

**Fix**: Enter a value in the required field or remove the row.

### Relation Not Found

**Cause**: The referenced record doesn't exist (e.g., a Company domain that wasn't imported).

**Fix**:

* Import the parent records first
* Or correct the reference value

See [Import Relations](/l/zh/user-guide/data-migration/capabilities/import-relations) for the correct import order and how to link records.

## Tips for Fewer Errors

1. **Download the template** to see expected format prior to importing your file
2. **Clean your data** in the spreadsheet first
3. **Import files in correct order** to import relations (Companies → People → Opportunities)
4. **Test with small batches** before full import
5. **Check for duplicates** before uploading
6. **Limit the size of your file to 10,000 records** per file
