Client scripts

  • Release version: Zurich
  • Updated May 18, 2026
  • 3 minutes to read
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    Summary of Client scripts

    Client scripts in ServiceNow enable running JavaScript in the user's web browser to respond to client-side events such as form loading, field changes, or form submission. They are designed to enhance the user experience by dynamically controlling form behavior, field visibility, read/write status, mandatory conditions, field values, choice list options, and displaying messages. However, client scripts are not a security measure and should not be relied upon to restrict data access; instead, use ACLs or data policies for that purpose.

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    Client scripts primarily run on forms and search pages, not on lists (except for onCellEdit() scripts) or ServiceNow mobile applications. For list editing validation or restrictions, other mechanisms like ACLs, business rules, data policies, or disabling list editing should be used.

    Key Features

    • Script Types:
      • onLoad(): Executes when a form first loads, allowing default values or form manipulation before user input.
      • onSubmit(): Executes during form submission to validate data; can cancel submission by returning false.
      • onChange(): Executes when a specified field value changes; provides parameters such as the control widget, old and new values, and loading status.
      • onCellEdit(): Executes when a list cell is edited, with parameters for sysids, table, old and new values, and a callback to manage script execution flow.
    • UI Type Targeting: Scripts can be configured to run in Desktop UI, Mobile/Service Portal UI, or all interfaces.
    • Field and Table Specificity: Scripts apply to specified tables and can be scoped globally or to particular views.
    • Script Isolation: By default, scripts run in strict mode with limited DOM, jQuery, and window object access for security. This can be adjusted per script or globally via system properties.
    • Localization Support: Messages can be defined for use within scripts to support multiple languages.

    Practical Use for ServiceNow Customers

    • Use client scripts to create responsive, dynamic forms that improve usability by automatically adjusting fields based on user roles or other field values.
    • Implement onSubmit client scripts to validate form data client-side before submission, reducing server load and improving feedback times.
    • For field-level dynamic changes, utilize onChange scripts, but remember these only apply on forms, not lists.
    • Manage list cell edits with onCellEdit scripts to validate or react to changes made directly in list views.
    • Remember to secure sensitive data access using ACLs or data policies, as client scripts alone cannot enforce data protection.
    • Configure scripts for the appropriate UI type to ensure they function as expected across desktop and mobile environments.

    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
    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 or Data policy.

    Where client scripts run

    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.
    Note:
    Client scripts are not supported on ServiceNow mobile applications.

    Client script form

    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.
    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.
    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.
    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.
    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.