# Category Schema (Ontologies)

A project’s category schema (also known as *ontology*) is the list of labeling tools available in the project.

Ango Hub allows project owners to set the project’s ontology directly from the *Category Schema* section of the *Settings* page.

<figure><img src="/files/GBcjrjjtSse9Lvjvk1lj" alt=""><figcaption></figcaption></figure>

The ontology created from this section is then reflected in the left sidebar of the labeling editor:

![](/files/mpojUbO7DggdyXINqbr2)

## How to create a project ontology <a href="#how-to-create-a-project-ontology" id="how-to-create-a-project-ontology"></a>

From the project’s *Settings* tab, enter the *Label Set* section.

Click on the *Add Category* button and choose the labeling tool to add. Each tool has a slightly different setup process. [See here for a list of all labeling tools available in Ango Hub, and how to add them to your project.](/labeling/labeling-tools.md)

For a guide on how to create nested classifications, [see here](/labeling/labeling-tools/tools/nested-classifications.md).

## How to copy a project's ontology to a new project

Please [check this guide](/how-to/transfer-project-ontologies-between-projects.md).

## Browse and Restore Previous Ontology Versions

From the Settings tab, in the *Category Schema* section, click on the "History" icon on the top-right to open a history of all workflow versions in the current project.

{% hint style="info" %}
Category Schema history started being recorded on March 12, 2025. Versions before then had not been saved.
{% endhint %}

<figure><img src="/files/GakeSqluF4KfxybsBiHU" alt=""><figcaption></figcaption></figure>

To view a previous version of this project's ontology, click on *Preview*. To restore it, click on *Save* while the version you need is previewed.


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