ServiceNow Field Types and Dictionary Entries Explained

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In ServiceNow, tables are only valid when you define fields that store meaningful data. Whether you’re adding a short description, capturing a phone number, or referencing another record, choosing the right field type is essential.

Beyond just adding fields, it’s equally important to understand how the data dictionary works, because this is where ServiceNow tracks field definitions, behaviours, and metadata. The dictionary entry is what makes each field in a table smart, consistent, and secure.

In this chapter, you’ll explore the different field types in ServiceNow, how to configure them using the sys_dictionary table, and how to use features like dictionary overrides and attributes to customize behavior.

What is a Field in ServiceNow?

A field in ServiceNow is a data container within a table. It holds a specific piece of information, such as a user name, date, priority, or reference to another table.

Each field has:

A name (the internal system name, e.g., short_description)
A label (the display name on forms and lists, e.g., Short Description)
A field type, which determines what kind of data it accepts

Fields are managed and stored through the sys_dictionary table, which forms the core of the ServiceNow data dictionary.

Understanding Field Types in ServiceNow

ServiceNow supports a variety of field types to support different use cases:

Field Type	Purpose
String	Stores short text values (e.g., titles, names)
Integer	Whole numbers only
Decimal	Floating-point numbers
Choice	Predefined drop-down options
Date/Time	Captures both date and time values
Reference	Links to another record in a different table
List	Allows selection of multiple values from another table
Boolean	True/False (usually displayed as a checkbox)
Journal	Stores comments or logs, typically for work notes
Attachment	Allows uploading of files to the record

For example, a list field type in ServiceNow allows you to select more than one item (e.g., assigning multiple users to a group), while a reference field connects your record to another table, such as linking an incident to a user.

Data Types vs. Field Types

It’s common to confuse data types with field types. In ServiceNow:

Field type: What you select when creating a field (e.g., String, Choice, Reference)
Data type: The technical format used in the database to store the value

While ServiceNow handles this behind the scenes, understanding the difference helps when designing tables or integrating with external databases.

How to View and Configure Dictionary Entries?

Every field in ServiceNow is defined and stored as a dictionary entry in the sys_dictionary table.

To view or edit a dictionary entry:

Right-click the field label on a form
Select Configure Dictionary

This opens the field’s dictionary record, where you can:

Change the field’s label or type
Define default values
Set field length or precision
Link to a reference table
Add dictionary attributes

You can also navigate directly to System Definition → Dictionary to view all entries across the platform.

Dictionary Attributes Explained

Dictionary attributes control field behavior beyond basic settings. These are additional properties you can add to dictionary entries to modify how fields behave in forms, lists, and logic.

Some common ServiceNow dictionary attributes include:

Attribute	Function
max_length	Limits the number of characters for string fields
ref_auto_completer	Enables auto-complete on reference fields
choice	Defines how choice fields behave (static/dynamic)
mandatory	Makes a field required
default_value	Sets the default input value for the field

These attributes are added as comma-separated values in the Attributes field of a dictionary entry.

Using Dictionary Overrides

When you extend a table (e.g., incident extends task), the child table inherits all the parent’s fields. But what if you want to customize one of those inherited fields? That’s where dictionary overrides come in.

A dictionary override allows you to:

Change the field label
Make the field read-only or mandatory
Set a different default value
Change visibility on forms

To configure it:

Go to System Definition → Dictionary Overrides
Select the parent field and the child table
Apply your changes specifically to that child table

This is especially useful when working with extended tables where some fields need to behave differently across child tables.

Best Practices for Managing Fields

Always use appropriate field types based on the data you’re storing
For multiple selections, use a list instead of multiple reference fields
Use reference fields to link tables instead of duplicating data
Leverage dictionary overrides instead of duplicating fields in extended tables
Avoid changing field types after a table has live data—it can cause data loss
Document your dictionary entries and attributes for future reference or audits

What’s Next?

Now that you understand how fields work and how to manage them through the data dictionary, we’ll move to the next layer: configuring forms and layouts. In the final chapter of this module, you’ll learn how to design clean, user-friendly forms by organizing fields, sections, and related lists.

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