ArcGIS service

An ArcGIS service is an item that wraps a URL to an external ArcGIS REST endpoint: a feature service, a map service, or a tiled image service. The portal doesn't copy the bytes; it queries the upstream service at render time and stores only the URL plus auth details on this item.

When to use this vs. a data layer

Pick ArcGIS service when:

• The authoritative data lives on someone else's AGO portal or ArcGIS Server and you don't own it.
• You're consuming a public REST service (USGS, FEMA, state GIS portals) and want it to appear as a citable item in your portal.
• You want changes upstream to appear immediately, without an ingest step.

Pick Data layer instead when:

• You can re-host the data and want the portal to own it (filtering, edits, derived layers, offline use, faster query).
• The upstream service is rate-limited, slow, or unreliable, and you'd rather cut the dependency.

Auth

Three modes:

• Anonymous. Public services with no token.
• Token (static). An ArcGIS token you obtained once and pasted in. The portal proxies requests, attaching the token. Tokens expire; the item carries a warning if it's within a week of expiry.
• Token (refreshable). Federated credentials. The portal refreshes the token automatically.

Tokens are stored encrypted at rest. The detail page never displays them; you can replace but not read.

What's stored

• Service URL and service type (feature service, map service, image service).
• Auth config (one of the modes above).
• Cached metadata. Layer list, schema, extent, the upstream server's reported max-record-count. Refreshed daily and on demand.

Use on a map

In the map builder, add as you would any other layer; the layer picker lists ArcGIS-service items the user can read. Each sublayer becomes its own map layer reference with its own styling, filter, and popup config. The portal renders by streaming features (or tiles, for image services) from the upstream service through its proxy.

Notes

• No edits. Even on a feature service that supports editing upstream, the portal proxies in read-only mode by default. There is no "publish edits to AGO from here" path.
• Pagination and limits. The portal honors the upstream's max-record-count; large queries page through in the background. A layer with millions of features may render slowly compared to a native data layer.
• Going dark. If the upstream service moves or expires, every map that references it shows a broken-layer marker. The dependency panel surfaces this.