> ## Documentation Index
> Fetch the complete documentation index at: https://docs.upstackdata.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Match Key Issues: Data Quality Problems in Customer Identifiers

> Track the number of match keys with data quality issues affecting Meta matching. Monitor email, phone, and other identifier fields to improve your EMQ score.

<Tip>
  The count of customer identifier fields (email, phone, etc.) that have data quality problems affecting Meta matching.
</Tip>

## Formula

<Info>
  **Match Key Issues** = **COUNT** ( Match Keys with Identified Issues )
</Info>

| Metadata        |                                   |
| --------------- | --------------------------------- |
| **Type**        | Number                            |
| **Data Source** | [Meta Ads](/sources/facebook-ads) |
| **Aggregation** | Count                             |

***

## Example

**Your pixel has 3 match key issues** flagged by Meta this week:

| Match Key   | Issue                   | Impact |
| ----------- | ----------------------- | ------ |
| Email       | Invalid format detected | High   |
| Phone       | Missing country codes   | Medium |
| External ID | Inconsistent hashing    | Low    |

***

## How It Works

Meta analyzes each customer identifier field you send with conversion events and flags issues that reduce matching accuracy. Common problems include invalid email formats, phone numbers without country codes, unhashed data, or inconsistent formatting across events.

***

## When to Use

| Scenario              | Action                                                                   |
| --------------------- | ------------------------------------------------------------------------ |
| Issue count increased | Review recent implementation changes to customer data capture            |
| Persistent high count | Audit data validation before sending events to Meta                      |
| Count dropped to zero | Confirm fixes resolved issues; monitor for regressions                   |
| New issue appeared    | Check the specific match key field for formatting or collection problems |

***

## Related Metrics

| Metric                                                                       | Relationship                                           |
| ---------------------------------------------------------------------------- | ------------------------------------------------------ |
| [Diagnostics Count](/reference/metrics/data-quality/emq/diagnostics-count)   | Total diagnostic issues (Match Key Issues is a subset) |
| [Match Key Coverage](/reference/metrics/data-quality/emq/match-key-coverage) | Coverage percentage for each identifier type           |

[See all EMQ metrics →](/reference/metrics/data-quality/emq)