# ESRI ArcGIS Online

ArcGIS Online is a web-based platform geographic information system (GIS). ArcGIS Online services are managed by Esri and accessed by a client running on a wide range of options.

The instructions that follow demonstrate how to connect to OS NGD API – Features using ESRI ArcGIS Online.

## What you need

* Access to the ESRI ArcGIS Online service.
* A preloaded base map, for example, [OS Maps API](/os-apis/accessing-os-apis/os-maps-api.md).
* OS NGD API – Features added to an API project in the OS Data Hub with an API Key. See [Getting started with an API](/os-apis/core-concepts/getting-started-with-an-api-project.md) project for more information.

## Instructions

{% stepper %}
{% step %}

### Add a new layer

Once you've signed into your ESRI ArcGIS Online account and opened the map viewer. Zoom in to a small area to reduce the number of requests that are initially sent to the API.

* Select *Layers* > *Add* > *Add layer from URL*.

<figure><img src="/files/e1a2d3bd0bf4b28259e7039d211ffedbcd20ef04" alt="ArcGIS Online Layers dialog."><figcaption><p>ArcGIS Online Layers dialog.</p></figcaption></figure>
{% endstep %}

{% step %}

### Add an API and set up custom parameters

In the Add Layer dialog:

* **URL**: Enter the base URL for OS NGD API – Features, excluding the API Key. For example, <https://api.os.uk/features/ngd/ofa/v1>.
* **Type**: Select *OGC feature layer*.
* Select *Custom request parameters* and enter the following:
  * **Parameter**: key
  * **Value**: \[Insert your OS API Key here]
* Click *Next*.

<figure><img src="/files/193d5c598d68ada3e0f72dbb6773a31bcbe34a5e" alt="ESRI ArcGIS Pro Add OGC API Server Connection dialog with URL and custom request parameters set."><figcaption><p>ESRI ArcGIS Pro Add OGC API Server Connection dialog with URL and custom request parameters set.</p></figcaption></figure>
{% endstep %}

{% step %}

### Adding layers to the map

In the Add Layer dialog:

* **To add a layer to the map**: Select a layer to add to the map and then click *Add to map*.

<figure><img src="/files/ed820b38524cca926e05ee6f4c7f4041ded77f54" alt="ArcGIS Online Add Layers dialog: Select a layer to add field."><figcaption><p>ArcGIS Online Add Layers dialog: Select a layer to add field.</p></figcaption></figure>

The layer will then display in the Layers panel and the data will display on the map:

<figure><img src="/files/f18c92809f5dc5657bc100fffacb2b44dafa89ec" alt="ArcGIS Online UI showing OS NGD API – Features data in the map area."><figcaption><p>ArcGIS Online UI showing OS NGD API – Features data in the map area.</p></figcaption></figure>

*Features will automatically refresh when you zoom or pan on the map. If you wish to add multiple layers to the same map, repeat steps 2 and 3.*
{% endstep %}
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