> For the complete documentation index, see [llms.txt](https://docs.api.ecoinvent.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.api.ecoinvent.org/overview/core-concepts.md).

# Core concepts

This guide will help you set up your initial access to the ecoinvent API.

### Versions & System Models

Ecoinvent operates on a versioned database system. Each API request that retrieves or processes data references a specific version and system model of the underlying environmental database.

* **Versions**: Represent different ecoinvent releases of the environmental database (e.g., "3.10", "3.12")
* **System Models**: Represent different modeling approaches within each ecoinvent version (e.g., "cutoff", "consequential"). For more information on the different system model feel free to check our knowledge base [here](https://support.ecoinvent.org/system-models).

All data retrieval endpoints (`/datasets` and `/indicators`) allow to specify which version and system model to use. If not explicitly provided, the API defaults to the latest available version and cutoff system model. The `/versions` endpoint allows you to discover all available combinations in your license.

### Dataset Identification (IDs)

ecoinvent uses several types of identifiers to reference datasets and methods:

* **Dataset ID**: A unique identifier (ID) that is automatically generated by the API, it does not change between versions.
* **Spold ID**: The API also supports lookup by UUIDs used in the ecoinvent SPOLD2 file format, these UUIDs can be for activities, geographies and products.

{% hint style="info" %}
It might happen that a dataset is merged, deleted, or manipulated which requires an ID change.
{% endhint %}

### LCIA methods & indicators

The ecoinvent database offers various indicators to assess environmental impact. Each indicator is part of a selected [method](https://support.ecoinvent.org/impact-assessment) and category. This means that the same indicator can have a different score, depending on the selected method & category. Call `GET /v3/api1/indicators` to retrieve all available combinations.

{% hint style="info" %}
Example: GWP100 is part of the IPCC 2021 method, but multiple categories (climate change: fossil, climate change: total, etc.). In this case, requesting GWP100 in each category will have its own ID and be reported as a separate indicator.
{% endhint %}

### API recommendation

For consistency across API usage, we recommend:

1. Use the search endpoint to find datasets and retrieve their computed IDs
2. Store these computed IDs for use with the `datasets` endpoint in subsequent requests
3. Make sure to use the correct IDs in new versions of the database, in case datasets or indicators change

{% hint style="info" %}
For more information about the ecoinvent database, visit our [Knowledge Base](https://support.ecoinvent.org/database)
{% endhint %}