--- sourceDocument: Yokohama API Reference sourceDocumentLink: https://www.servicenow.com/docs/r/yokohama/api-reference Release : - yokohama ft:locale : - en-US ft:publication_title : - Yokohama API Reference ft:clusterId : - crapiref bundleId : - crapiref workflow : - Creator --- # Client scripts # Client scripts {#ariaid-title1} * Release version: Yokohama * * Updated May 18, 2026 * * ![](https://www.servicenow.com/docs/portal-asset/ico-clock) 3 minutes to read Summarize ![AI sparkle icon](https://servicenow.com/docs/portal-asset/ai-sparkle-icon) Summarized using AI This content was generated using new OpenAI-powered functionality. Results are provided on an as is basis and are not guaranteed to be accurate or complete. ## Summary of Client scripts Client scripts in ServiceNow enable running JavaScript directly in the user's web browser to respond to client-side events such as form loading, field changes, and form submission. They help configure forms and fields dynamically to enhance the user experience by controlling field visibility, editability, mandatory status, and default values during form interaction. Show full answer Show less Client scripts are designed for user interface optimization and should not be relied on for data security. To protect sensitive data, use Access Control Lists (ACLs) or Data Policies instead. ## Where Client Scripts Run Client scripts (except `onCellEdit()`) apply only to forms and search pages, not lists. To manage field values on lists, use ACLs, business rules, data policies, or `onCellEdit()` client scripts. Client scripts are not supported in ServiceNow mobile apps. ## Key Client Script Types and Their Use * **onLoad()**: Executes when the form initially loads, useful for setting default values or manipulating form elements before user input. * **onSubmit()**: Runs on form submission to validate inputs; can cancel submission by returning false. * **onChange()**: Triggers when a specific field value changes; receives parameters such as the changed control, old and new values, and flags to identify if the change is during form or template loading. * **onCellEdit()**: Executes when a list editor cell value is changed, with parameters for the records edited, old and new values, and a callback to manage script execution flow. ## Configuration Fields and Their Practical Use * **Name:** Identify the client script. * **Table:** Specify the table the script applies to. * **UI Type:** Target user interface(s) where the script runs---Desktop, Mobile/Service Portal, or All. * **Field Name:** Specify the field for `onChange()` or `onCellEdit()` scripts. * **Application:** Define the application context. * **Active:** Enable or disable the client script. * **Inherited:** Indicates if the script applies to extended tables. * **Global and View:** Control script scope across views. * **Description:** Document the script's purpose. * **Messages:** Define localized messages accessible via the script for better internationalization support. * **Script:** Contains the actual JavaScript code executed on the client side. * **Isolate script:** Controls strict mode execution; strict mode disables direct DOM and certain global object access for security and stability. It can be disabled per script or globally via a system property. ## Practical Considerations for ServiceNow Customers * Use client scripts to improve form usability by dynamically controlling fields based on user actions or roles. * Do not rely on client scripts for security; always enforce data protection via ACLs and data policies. * Choose the appropriate client script type based on the event you want to respond to (loading, submission, field change, or list editing). * Configure UI Type carefully to ensure scripts run only where intended (desktop vs. mobile/portal). * Leverage localized messages within client scripts to support multi-language environments. * Understand the impact of strict mode on script capabilities and enable DOM access only when necessary. Client scripts allow the system to run JavaScript on the client (web browser) when client-based events occur, such as when a form loads, after form submission, or when a field changes value.
Use client scripts to configure forms, form fields, and field values while the user is using the form. Client scripts can: * make fields hidden or visible * make fields read only or writable * make fields optional or mandatory based on the user's role * set the value in one field based on the value in other fields * modify the options in a choice list based on a user's role * display messages based on a value in a field {#client-scripts__ul_zp5_n5y_vdb} Warning: Client scripts are intended to optimize the user experience on a form. Client scripts are not meant to protect unwanted access to data. To prevent unwanted access to data, ensure that sensitive fields are hidden or read-only through ACLs or data policies. For more information, see [Access Control List Rules](https://www.servicenow.com/docs/access?context=access-control-rules&version=yokohama&pubname=yokohama-platform-security&ft:locale=en-US) or [Data policy](https://www.servicenow.com/docs/access?context=c_DataPolicy&version=yokohama&pubname=yokohama-platform-administration&ft:locale=en-US). ## Where client scripts run {#client-scripts__section_y1n_4z5_zz} With the exception of onCellEdit() client scripts, client scripts only apply to forms and search pages. If you create a client script to control field values on a form, you must use one of these other methods to control field values when on a list. * Create an access control to restrict who can edit field values. * Create a business rule to validate content. * Create a data policy to validate content. * Create an onCellEdit() client script to validate content. * Disable list editing for the table. {#client-scripts__ul_nml_51t_d1b} Note: Client scripts are not supported on ServiceNow mobile applications. ## Client script form {#client-scripts__section_yjd_hvg_zz} {#client-scripts__table_trz_nvg_zz__entry__2} | Field | Description | |-|-| | Name | Name of the client script. | | Table | Table to which the client script applies. | | UI Type | Target user interface to which the client script applies. * Desktop: The script runs only in the desktop Core UI. * Mobile / Service Portal: The script runs only in mobile, portal, or configurable workspace UIs. * All: The script executes across all available UIs. {#client-scripts__ul_b1b_ssm_hjc} | | Type | onLoad() --- runs when the system first renders the form and before users can enter data. Typically, onLoad() client scripts perform client-side-manipulation of the current form or set default record values. onSubmit() --- runs when a form is submitted. Typically, onSubmit() scripts validate things on the form and ensure that the submission makes sense. An onSubmit() client script can cancel form submission by returning a value of false. onChange() --- runs when a particular field value changes on the form. The onChange() client script must specify these parameters. * control: the DHTML widget whose value changed. Note: control is not accessible in mobile and service portal. * oldValue: the value the widget had when the record was loaded. Note: Old values aren't returned for the HTML field type. * newValue: the value the widget has after the change. * isLoading: identifies whether the change occurs as part of a form load. * isTemplate: identifies whether the change occurs as part of a template load. {#client-scripts__ul_bsg_d2r_n4} onCellEdit() --- runs when the list editor changes a cell value. The onCellEdit() client script must specify these parameters. * sysIDs: an array of the sys_ids for all items being edited. * table: the table of the items being edited. * oldValues: the old values of the cells being edited. * newValue: the new value for the cells being edited. * callback: a callback that continues the execution of any other related cell edit scripts. If true is passed as a parameter, the other scripts are executed or the change is committed if there are no more scripts. If false is passed as a parameter, any further scripts are not executed and the change is not committed. {#client-scripts__ul_qm5_z2r_n4} | | Field Name | Name of the field to which the script applies. Available only if the script responds to a field value change (onChange or onCellEdit script types). | | Application | Application where this client script resides. | | Active | Enables the client script when selected. Unselect this field to disable the client script. | | Inherited | Indicates whether the client script applies to extended tables. | | Global | If true, the client script runs on all views of the table. | | View | Only visible when Global is unselected. Views on which the client script will run. | | Description | Content describing the functionality and purpose of the client script. | | Messages | Text string (one per line) available to the client script as localized messages using getmessage('\[message\]'). For additional information, see [Translate a client script message](https://www.servicenow.com/docs/access?context=t_TranslateAClientScriptMessage&version=yokohama&pubname=yokohama-platform-administration&ft:locale=en-US). | | Script | Contains the client script. | | Isolate script | New client scripts are run in strict mode, in which direct DOM access is turned off. Access to jQuery, prototype, and the window object are also turned off by default. To enable DOM access on a per-script basis, leave the Isolate script option cleared. To turn off strict mode for all new globally scoped client scripts, set the glide.script.block.client.globals system property to false. | [ ] {#client-scripts__table_trz_nvg_zz} **Related concepts** * [Client API reference](https://www.servicenow.com/docs/q5afiHTjy4_Er70vupCs7Q "Use client-side JavaScript APIs to control aspects of how ServiceNow AI Platform is displayed and functions within the web browser. This reference lists available classes and methods along with parameters, descriptions, and examples to help control the end-user experience.")