---
schema_version: "1"
id: d3f88193e48b94075165a5481a4c5b8fb10aac9025c5982d238b6c9651ecd5c7
title: Validate Support for Callback URL Expressions
collection: admin
version: current
locale: en-us
portal_url: https://docs.salesforce.com/admin/current/en-us/platform/264-0-0/external_services_async_ops_validate_support.md
canonical_url: https://help.salesforce.com/s/articleView?id=platform.external_services_async_ops_validate_support.htm&release=264.0.0&type=5
source_site: help.salesforce.com
content_type: documentation
content_hash: 7365ea54c59062cb23c7b5e10b2bb06ecaab31fbdc57244669cb45c83365bf67
description: Verify that your callback URL expression is supported and registered by External Services as an asynchronous action.
products:
  - Salesforce Platform
  - Security
release: "264"
---
# Validate Support for Callback URL Expressions

Verify that your callback URL expression is supported and registered by External Services as an asynchronous action.

### Required Editions

<table class="slds-table slds-table_bordered slds-max-medium-table_stacked slds-m-bottom_small edition"><colgroup><col></colgroup><tbody><tr class=""><td class="slds-cell-wrap" style="vertical-align:top;">Available in: Lightning Experience</td></tr><tr class=""><td class="slds-cell-wrap" style="vertical-align:top;">Available in: <strong>Enterprise</strong>, <strong>Performance</strong>, <strong>Unlimited</strong>, and <strong>Developer</strong> Editions</td></tr></tbody></table>

For supported callback expressions, see [External Services Asynchronous Callbacks](https://help.salesforce.com/s/articleView?id=platform.external_services_schema_def_usage_considerations.htm&release=264.0.0&type=5).

1. From Setup, in the Quick Find box, enter External Services, and then select **External Services**.
2. Register the API specification that contains the callback expression.
3. Navigate to the Detail page of the external service that contains the callback operation.
    
    - If the callback expression is supported for a given operation, then the **Callback Parameter** column lists the callback parameter names.
    - If there’s no value in the **Callback Parameters** column, then the callback expression isn’t supported, or the operation doesn’t contain a callback operation.

![Note](https://sf-zdocs-cdn-prod.zoominsoftware.com/tdta-platform-extend_click-264-0-0-production-enus/5f7d9219-b7b1-4552-8891-f1aba9b289fc/images/icon_note.png)

Note If the callback isn’t supported, External Services attempts to register the operation as a normal, synchronous operation with a 120-second timeout on all callouts.