Home → API Documentation → Miscellaneous API Calls → api/UpdateCustomField

11.6. api/UpdateCustomField

This API call updates one custom field on an existing contact, company or event record. First, call api/ReturnCustomFields to obtain the appropriate FieldGUID. The field identifier determines the record type being updated. 

 

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Parameters To Submit

All parameters are required and cannot be empty.

Parameter	Parameter Help
uid	The GUID of the record being updated: ContactGUID, CompanyGUID or EventGUID.
FieldGUID	The custom field identifier returned by api/ReturnCustomFields.
UpdateValue	The new value to save, formatted for the field type.
API Key

 

For a company field, uid must identify the company being updated. For an event field, it must identify the event.

 

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Field Value Formats 

Field Type	Example UpdateValue	Notes
Text	Example text	Saves the supplied text.
Boolean	True or False	True saves Y; False saves an empty value. 1 and 0 are also accepted.
Date	21/10/2026	An ISO date such as 2026-10-21 is also accepted.
DateTime	21/10/2026 14:35:00	An ISO value such as 2026-10-21T14:35:00 is also accepted.
Number / Decimal	123 / 1234.56	Submit the value as a string.
Email / Hyperlink	test@example.com / https://example.com	Saves the supplied value.
HTML Editor	<p>Example <strong>text</strong></p>	Submit the HTML as a string.
Dropdown - Single Select	An existing option’s stored value	Use the value expected by the CRM field.
Dropdown - Multi Select	MultiItem1¬MultiItem2¬	Separate options with ¬, including after the last option.

 

For Multi Select fields, use existing option values. The procedure adds a missing final ¬ and also accepts comma-separated input when no ¬ separator is supplied. 

 

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Return Response

This API call will return a Boolean of True if successful.