> For the complete documentation index, see [llms.txt](https://revstack.gitbook.io/docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://revstack.gitbook.io/docs/getting-started/manage-duplicates.md).

# Manage duplicates

## Check duplicate documents

<figure><img src="/files/ZEYoAlSul7Pi7SmY3sDs" alt=""><figcaption></figcaption></figure>

Duplicate documents can appear in your collection when importing data from multiple bibliographic sources or adding documents manually. Revstack automatically scans new documents for duplicates upon import. The system detects duplicates based on key metadata such as DOI, PMC, PMCID and Title (optional).

Duplicates numbers detected are provider directly in the Documents section. To review duplicates:

{% stepper %}
{% step %}
Navigate to the "Documents" section of your collection.
{% endstep %}

{% step %}
Click on "Check duplicate" button.
{% endstep %}
{% endstepper %}

## Merging duplicate documents

<figure><img src="/files/vZxTkKHhtQzSNgjAh3zg" alt=""><figcaption></figcaption></figure>

When duplicates are detected, you can merge them to keep a single, consolidated version with the most complete metadata. To merge duplicates:

1. Select the prefered database source.
2. Choose the metadata criteria for merging documents. By default, only primary identifiers such as DOI, PMC, and PMCID are used. If you want to merge documents with the same title, you can specify this option at this stage.
3. Enable the metadata consolidation option if you want Revstack to combine metadata from the duplicates while merging.
4. Click the "Merge Duplicate" button to complete the process.

## Restore duplicate documents

You can restore duplicate documents at any stage by returning to the Duplicate document section.