Once you have created a topology and loaded data, you can run a validation against the feature class contents of the topology. The validation process performs the following tasks:
- Cracks and clusters feature vertices to find features that share geometry (common coordinates)
- Inserts common coordinate vertices into features that share geometry
- Runs a set of integrity checks to identify any violations of the rules that have been defined for the topology
There are several ways to validate a topology. You can use the Error Inspector, or you can use the Validate Topology geoprocessing tool to validate a topology in the map or as part of an automated workflow. Scripts can be useful for automating a series of tasks and for building repeatable workflows.
Note:
A key difference between the Error Inspector and the Validate Topology geoprocessing tool is the tool always run asynchronously and provides options to validate either the full extent of the topology or the current visible extent of the topology feature service. Using the Validate button in the Error Inspector runs synchronously for the topology within the visible extent of the active map. If you anticipate your validation process may be lengthy or if you're validating against the full extent of the feature service, it is recommended that you use the Validate Topology geoprocessing tool.Once a new topology has been validated, subsequent edits are noted with dirty areas that identify features in the associated layers participating in the topology that require revalidation. This saves time and improves performance, because only the areas that need to be revalidated are processed.
Validate topology using the Error Inspector
You can validate a topology published as a feature layer using the Error Inspector in ArcGIS Pro. Before completing the steps below, the topology and its associated layers must be published as a web feature layer with the Version Management and Validation capabilities enabled. See Share and use a topology for more information.
- In the Catalog pane, click the Portal tab.
- Locate and double-click the topology web feature layer containing the data to validate.
- Right-click the individual topology layer and click Add to New > Map
or Add to Current Map 
. - On the Edit tab, in the Manage Edits group, click Error Inspector
.
The Error Inspector toolbar appears. The Source option on this toolbar references the topology feature layer in the current map view.
- Optionally, click the Source drop-down button and choose the topology web feature layer to change the value.
- Ensure that you lined up the visible extent to reflect the area you want to validate.
- Click the Validate button
to begin the process of validating against the topology rules defined in the source topology feature layer. 
Note:
The Validate button on the Error Inspector toolbar runs synchronously when evaluating the topology within the visible extent of the active map.
Once the topology is validated, learn about previewing errors, viewing error details, exporting topology errors, and fixing topology errors.
Validate topology using the Validate Topology geoprocessing tool
Complete the following steps to use the Validate Topology geoprocessing tool to validate the topology against the topology rules defined in the source topology.
Note:
When the input topology is from a topology layer feature service, the tool performs the validate process asynchronously.
- In ArcGIS Pro, in the Geoprocessing pane, search for and select the Validate Topology geoprocessing tool.
The Validate Topology dialog box appears.
- For Input Topology, use the browse button to browse to the topology you want to validate. If the topology is in your map, in the Contents pane, drag the layer to the Input Topology parameter text box.
Starting at ArcGIS Pro 2.6, the input topology layer can be from a topology service if the service is published with ArcGIS Enterprise 10.8.1 or later. In this scenario, you also have the option of providing the URL of the topology layer feature service for the Input Topology parameter, for example, https://myserver.mydomain.com/server/rest/services/myTopoService/FeatureServer/0.
Tip:
The extent of the topology that will be validated can be specified as follows:
-
If the tool is being used while the topology layer is open in the map, only the current visible extent in the map display is validated.
If the tool references a topology not displayed in the map, the entire extent of the topology is validated. This is the default.
If the tool is run in the Python window or in a Python script, the entire extent of the topology is validated regardless of this parameter setting.
-
Once the topology is validated, learn about previewing errors, viewing error details, exporting topology errors, and fixing topology errors.
Topology validation tips
Keep the following in mind when validating topology:
- You can choose when and how often you validate the topology. Typically, each topology must be validated in its entirety only once. All other validations only revalidate dirty areas where changes have occurred.
- ArcGIS automatically tracks dirty areas as you edit your data as well as when you change the topology definition. When you validate the topology, ArcGIS automatically identifies the dirty areas to be validated.
- How often should you validate the topology? It is best to validate the topology anytime you edit the features in the associated layers participating in the topology. You can also validate portions of the dataset during editing so you can find and fix errors during the editing process.
- If you change the topology definition, you may need to revalidate the topology. For example, if you change the topology rule or the coordinate ranks, the entire topology is flagged as dirty and will be revalidated the next time you run validation.
- Revalidating the topology does not mean that cluster processing will cause the coordinates to move more in each subsequent validation. Once you have clustered the coordinates in the initial validation, they will not move in subsequent validations unless new geometries have been added that fall within the x,y tolerance of existing features (for example, when you connect a new road to a street network, split a parcel, and so forth). In these cases, only the changed areas where vertices fall within the cluster tolerance of other features will be clustered and, potentially. adjusted.
- The feature classes that participate in a topology are always available for use in ArcGIS regardless of whether the topology has been recently validated. If the topology has not been validated, some of the features may not adhere to the integrity rules. However, they are available for use—with or without errors.