diff --git a/packages/payload/src/collections/config/client.ts b/packages/payload/src/collections/config/client.ts
index 6b79cb5ef..5ca0f2646 100644
--- a/packages/payload/src/collections/config/client.ts
+++ b/packages/payload/src/collections/config/client.ts
@@ -2,7 +2,7 @@ import type { LivePreviewConfig, ServerOnlyLivePreviewProperties } from '../../c
 
 export type ServerOnlyCollectionProperties = keyof Pick<
   SanitizedCollectionConfig,
-  'access' | 'endpoints' | 'hooks'
+  'access' | 'custom' | 'endpoints' | 'hooks'
 >
 
 export type ServerOnlyCollectionAdminProperties = keyof Pick<
@@ -44,6 +44,7 @@ export const createClientCollectionConfig = ({
     'hooks',
     'access',
     'endpoints',
+    'custom',
     // `upload`
     // `admin`
     // are all handled separately
@@ -77,12 +78,6 @@ export const createClientCollectionConfig = ({
     })
   }
 
-  if ('custom' in sanitized && sanitized.custom) {
-    if ('server' in sanitized.custom && sanitized.custom.server) {
-      delete sanitized.custom.server
-    }
-  }
-
   if ('admin' in sanitized) {
     sanitized.admin = { ...sanitized.admin }
 
diff --git a/packages/payload/src/collections/config/defaults.ts b/packages/payload/src/collections/config/defaults.ts
index 696e14476..7ade12204 100644
--- a/packages/payload/src/collections/config/defaults.ts
+++ b/packages/payload/src/collections/config/defaults.ts
@@ -10,6 +10,7 @@ export const defaults = {
   },
   admin: {
     components: {},
+    custom: {},
     enableRichTextLink: true,
     enableRichTextRelationship: true,
     pagination: {
diff --git a/packages/payload/src/collections/config/schema.ts b/packages/payload/src/collections/config/schema.ts
index 8c66d78e4..c0bc467d0 100644
--- a/packages/payload/src/collections/config/schema.ts
+++ b/packages/payload/src/collections/config/schema.ts
@@ -57,6 +57,7 @@ const collectionSchema = joi.object().keys({
         ),
       }),
     }),
+    custom: joi.object().pattern(joi.string(), joi.any()),
     defaultColumns: joi.array().items(joi.string()),
     description: joi.alternatives().try(joi.string(), componentSchema),
     enableRichTextLink: joi.boolean(),
@@ -107,10 +108,7 @@ const collectionSchema = joi.object().keys({
     }),
     joi.boolean(),
   ),
-  custom: joi.object().keys({
-    client: joi.object().pattern(joi.string(), joi.any()),
-    server: joi.object().pattern(joi.string(), joi.any()),
-  }),
+  custom: joi.object().pattern(joi.string(), joi.any()),
   dbName: joi.alternatives().try(joi.string(), joi.func()),
   defaultSort: joi.string(),
   disableDuplicate: joi.bool(),
diff --git a/packages/payload/src/collections/config/types.ts b/packages/payload/src/collections/config/types.ts
index e8229c2e0..9c782bddf 100644
--- a/packages/payload/src/collections/config/types.ts
+++ b/packages/payload/src/collections/config/types.ts
@@ -246,6 +246,8 @@ export type CollectionAdminOptions = {
         | React.ComponentType<any>
     }
   }
+  /** Extension point to add your custom data. Available in server and client. */
+  custom?: Record<string, any>
   /**
    * Default columns to show in list view
    */
@@ -314,17 +316,8 @@ export type CollectionConfig = {
    * Use `true` to enable with default options
    */
   auth?: IncomingAuthType | boolean
-  /** Extension point to add your custom data. */
-  custom?: {
-    /**
-     * Available in client bundle.
-     */
-    client?: Record<string, any>
-    /**
-     * Server only.
-     */
-    server?: Record<string, any>
-  }
+  /** Extension point to add your custom data. Server only. */
+  custom?: Record<string, any>
   /**
    * Default field to sort by in collection list view
    */
diff --git a/packages/payload/src/config/client.ts b/packages/payload/src/config/client.ts
index d85901d2c..9768a9a3d 100644
--- a/packages/payload/src/config/client.ts
+++ b/packages/payload/src/config/client.ts
@@ -18,6 +18,7 @@ export type ServerOnlyRootProperties = keyof Pick<
   | 'bin'
   | 'cors'
   | 'csrf'
+  | 'custom'
   | 'db'
   | 'editor'
   | 'email'
@@ -40,6 +41,7 @@ export type ClientConfig = Omit<
     livePreview?: Omit<LivePreviewConfig, ServerOnlyLivePreviewProperties>
   }
   collections: ClientCollectionConfig[]
+  custom?: Record<string, any>
   globals: ClientGlobalConfig[]
 }
 
@@ -67,6 +69,7 @@ export const createClientConfig = async ({
     'cors',
     'csrf',
     'email',
+    'custom',
     // `admin`, `onInit`, `localization`, `collections`, and `globals` are all handled separately
   ]
 
@@ -84,12 +87,6 @@ export const createClientConfig = async ({
     })
   }
 
-  if ('custom' in clientConfig && clientConfig.custom) {
-    if ('server' in clientConfig.custom && clientConfig.custom.server) {
-      delete clientConfig.custom.server
-    }
-  }
-
   if ('admin' in clientConfig) {
     clientConfig.admin = { ...clientConfig.admin }
 
diff --git a/packages/payload/src/config/defaults.ts b/packages/payload/src/config/defaults.ts
index c75400475..fb522c5ac 100644
--- a/packages/payload/src/config/defaults.ts
+++ b/packages/payload/src/config/defaults.ts
@@ -4,6 +4,7 @@ export const defaults: Omit<Config, 'db' | 'editor' | 'secret'> = {
   admin: {
     avatar: 'default',
     components: {},
+    custom: {},
     dateFormat: 'MMMM do yyyy, h:mm a',
     disable: false,
     inactivityRoute: '/logout-inactivity',
diff --git a/packages/payload/src/config/schema.ts b/packages/payload/src/config/schema.ts
index 85bfdb5f2..570599fba 100644
--- a/packages/payload/src/config/schema.ts
+++ b/packages/payload/src/config/schema.ts
@@ -57,6 +57,7 @@ export default joi.object({
         joi.object().pattern(joi.string(), component),
       ),
     }),
+    custom: joi.object().pattern(joi.string(), joi.any()),
     dateFormat: joi.string(),
     disable: joi.bool(),
     inactivityRoute: joi.string(),
@@ -83,10 +84,7 @@ export default joi.object({
   cookiePrefix: joi.string(),
   cors: [joi.string().valid('*'), joi.array().items(joi.string())],
   csrf: joi.array().items(joi.string().allow('')).sparse(),
-  custom: joi.object().keys({
-    client: joi.object().pattern(joi.string(), joi.any()),
-    server: joi.object().pattern(joi.string(), joi.any()),
-  }),
+  custom: joi.object().pattern(joi.string(), joi.any()),
   db: joi.any(),
   debug: joi.boolean(),
   defaultDepth: joi.number().min(0).max(30),
diff --git a/packages/payload/src/config/types.ts b/packages/payload/src/config/types.ts
index 4a4ca355e..9f991a8b9 100644
--- a/packages/payload/src/config/types.ts
+++ b/packages/payload/src/config/types.ts
@@ -417,9 +417,9 @@ export type Config = {
           prefillOnly?: boolean
         }
       | false
-
     /** Set account profile picture. Options: gravatar, default or a custom React component. */
     avatar?: 'default' | 'gravatar' | React.ComponentType<any>
+
     /**
      * Add extra and/or replace built-in components with custom components
      *
@@ -489,6 +489,8 @@ export type Config = {
         Dashboard?: AdminView
       }
     }
+    /** Extension point to add your custom data. Available in server and client. */
+    custom?: Record<string, any>
     /** Global date format that will be used for all dates in the Admin panel. Any valid date-fns format pattern can be used. */
     dateFormat?: string
     /** If set to true, the entire Admin panel will be disabled. */
@@ -547,17 +549,8 @@ export type Config = {
   /** A whitelist array of URLs to allow Payload cookies to be accepted from as a form of CSRF protection. */
   csrf?: string[]
 
-  /** Extension point to add your custom data. */
-  custom?: {
-    /**
-     * Available in client bundle.
-     */
-    client?: Record<string, any>
-    /**
-     * Server only.
-     */
-    server?: Record<string, any>
-  }
+  /** Extension point to add your custom data. Server only. */
+  custom?: Record<string, any>
 
   /** Pass in a database adapter for use on this project. */
   db: DatabaseAdapterResult
diff --git a/packages/payload/src/fields/config/client.ts b/packages/payload/src/fields/config/client.ts
index 066b4cd70..201e817b9 100644
--- a/packages/payload/src/fields/config/client.ts
+++ b/packages/payload/src/fields/config/client.ts
@@ -8,7 +8,7 @@ export type ServerOnlyFieldProperties =
   | 'editor' // This is a `richText` only property
   | 'filterOptions' // This is a `relationship` and `upload` only property
   | 'label'
-  | keyof Pick<FieldBase, 'access' | 'defaultValue' | 'hooks' | 'validate'>
+  | keyof Pick<FieldBase, 'access' | 'custom' | 'defaultValue' | 'hooks' | 'validate'>
 
 export type ServerOnlyFieldAdminProperties = keyof Pick<
   FieldBase['admin'],
@@ -32,6 +32,7 @@ export const createClientFieldConfig = ({
     'label',
     'filterOptions', // This is a `relationship` and `upload` only property
     'editor', // This is a `richText` only property
+    'custom',
     // `fields`
     // `blocks`
     // `tabs`
@@ -45,12 +46,6 @@ export const createClientFieldConfig = ({
     }
   })
 
-  if ('custom' in field && field.custom) {
-    if ('server' in field.custom && field.custom.server) {
-      delete field.custom.server
-    }
-  }
-
   if ('options' in field && Array.isArray(field.options)) {
     field.options = field.options.map((option) => {
       if (typeof option === 'object' && typeof option.label === 'function') {
diff --git a/packages/payload/src/fields/config/schema.ts b/packages/payload/src/fields/config/schema.ts
index 07c0e6bf6..ac720fea2 100644
--- a/packages/payload/src/fields/config/schema.ts
+++ b/packages/payload/src/fields/config/schema.ts
@@ -15,6 +15,7 @@ export const baseAdminFields = joi.object().keys({
   className: joi.string(),
   components: baseAdminComponentFields,
   condition: joi.func(),
+  custom: joi.object().pattern(joi.string(), joi.any()),
   description: joi
     .alternatives()
     .try(joi.string(), joi.object().pattern(joi.string(), [joi.string()]), componentSchema),
@@ -37,10 +38,7 @@ export const baseField = joi
       update: joi.func(),
     }),
     admin: baseAdminFields.default(),
-    custom: joi.object().keys({
-      client: joi.object().pattern(joi.string(), joi.any()),
-      server: joi.object().pattern(joi.string(), joi.any()),
-    }),
+    custom: joi.object().pattern(joi.string(), joi.any()),
     hidden: joi.boolean().default(false),
     hooks: joi
       .object()
@@ -422,10 +420,10 @@ export const blocks = baseField.keys({
     .items(
       joi.object({
         slug: joi.string().required(),
-        custom: joi.object().keys({
-          client: joi.object().pattern(joi.string(), joi.any()),
-          server: joi.object().pattern(joi.string(), joi.any()),
+        admin: joi.object().keys({
+          custom: joi.object().pattern(joi.string(), joi.any()),
         }),
+        custom: joi.object().pattern(joi.string(), joi.any()),
         dbName: joi.alternatives().try(joi.string(), joi.func()),
         fields: joi.array().items(joi.link('#field')),
         graphQL: joi.object().keys({
@@ -522,14 +520,12 @@ export const ui = joi.object().keys({
         })
         .default({}),
       condition: joi.func(),
+      custom: joi.object().pattern(joi.string(), joi.any()),
       position: joi.string().valid('sidebar'),
       width: joi.string(),
     })
     .default(),
-  custom: joi.object().keys({
-    client: joi.object().pattern(joi.string(), joi.any()),
-    server: joi.object().pattern(joi.string(), joi.any()),
-  }),
+  custom: joi.object().pattern(joi.string(), joi.any()),
   label: joi.alternatives().try(joi.string(), joi.object().pattern(joi.string(), [joi.string()])),
 })
 
diff --git a/packages/payload/src/fields/config/types.ts b/packages/payload/src/fields/config/types.ts
index 8af130f20..9303a4b55 100644
--- a/packages/payload/src/fields/config/types.ts
+++ b/packages/payload/src/fields/config/types.ts
@@ -124,6 +124,8 @@ type Admin = {
    * This is also run on the server, to determine if the field should be validated.
    */
   condition?: Condition
+  /** Extension point to add your custom data. Available in server and client. */
+  custom?: Record<string, any>
   description?: Description
   disableBulkEdit?: boolean
   disabled?: boolean
@@ -179,17 +181,8 @@ export interface FieldBase {
     update?: FieldAccess
   }
   admin?: Admin
-  /** Extension point to add your custom data. */
-  custom?: {
-    /**
-     * Available in client bundle.
-     */
-    client?: Record<string, any>
-    /**
-     * Server only.
-     */
-    server?: Record<string, any>
-  }
+  /** Extension point to add your custom data. Server only. */
+  custom?: Record<string, any>
   defaultValue?: any
   hidden?: boolean
   hooks?: {
@@ -430,21 +423,14 @@ export type UIField = {
       Filter?: React.ComponentType<any>
     }
     condition?: Condition
+    /** Extension point to add your custom data. Available in server and client. */
+    custom?: Record<string, any>
     disableBulkEdit?: boolean
     position?: string
     width?: string
   }
-  /** Extension point to add your custom data. */
-  custom?: {
-    /**
-     * Available in client bundle.
-     */
-    client?: Record<string, any>
-    /**
-     * Server only.
-     */
-    server?: Record<string, any>
-  }
+  /** Extension point to add your custom data. Server only. */
+  custom?: Record<string, any>
   label?: Record<string, string> | string
   name: string
   type: 'ui'
@@ -655,17 +641,12 @@ export type RadioField = FieldBase & {
 }
 
 export type Block = {
-  /** Extension point to add your custom data. */
-  custom?: {
-    /**
-     * Available in client bundle.
-     */
-    client?: Record<string, any>
-    /**
-     * Server only.
-     */
-    server?: Record<string, any>
+  admin?: {
+    /** Extension point to add your custom data. Available in server and client. */
+    custom?: Record<string, any>
   }
+  /** Extension point to add your custom data. Server only. */
+  custom?: Record<string, any>
   /**
    * Customize the SQL table name
    */
diff --git a/packages/payload/src/globals/config/client.ts b/packages/payload/src/globals/config/client.ts
index 0a1a7aecd..dc3b12c69 100644
--- a/packages/payload/src/globals/config/client.ts
+++ b/packages/payload/src/globals/config/client.ts
@@ -12,7 +12,7 @@ import { createClientFieldConfigs } from '../../fields/config/client.js'
 
 export type ServerOnlyGlobalProperties = keyof Pick<
   SanitizedGlobalConfig,
-  'access' | 'admin' | 'endpoints' | 'fields' | 'hooks'
+  'access' | 'admin' | 'custom' | 'endpoints' | 'fields' | 'hooks'
 >
 export type ServerOnlyGlobalAdminProperties = keyof Pick<
   SanitizedGlobalConfig['admin'],
@@ -46,6 +46,7 @@ export const createClientGlobalConfig = ({
     'hooks',
     'access',
     'endpoints',
+    'custom',
     // `admin` is handled separately
   ]
 
@@ -55,12 +56,6 @@ export const createClientGlobalConfig = ({
     }
   })
 
-  if ('custom' in sanitized && sanitized.custom) {
-    if ('server' in sanitized.custom && sanitized.custom.server) {
-      delete sanitized.custom.server
-    }
-  }
-
   if ('admin' in sanitized) {
     sanitized.admin = { ...sanitized.admin }
 
diff --git a/packages/payload/src/globals/config/schema.ts b/packages/payload/src/globals/config/schema.ts
index 95ab99451..7a40ebca1 100644
--- a/packages/payload/src/globals/config/schema.ts
+++ b/packages/payload/src/globals/config/schema.ts
@@ -39,6 +39,7 @@ const globalSchema = joi
           ),
         }),
       }),
+      custom: joi.object().pattern(joi.string(), joi.any()),
       description: joi.alternatives().try(joi.string(), componentSchema),
       group: joi
         .alternatives()
@@ -48,10 +49,7 @@ const globalSchema = joi
       livePreview: joi.object(livePreviewSchema),
       preview: joi.func(),
     }),
-    custom: joi.object().keys({
-      client: joi.object().pattern(joi.string(), joi.any()),
-      server: joi.object().pattern(joi.string(), joi.any()),
-    }),
+    custom: joi.object().pattern(joi.string(), joi.any()),
     dbName: joi.alternatives().try(joi.string(), joi.func()),
     endpoints: endpointsSchema,
     fields: joi.array(),
diff --git a/packages/payload/src/globals/config/types.ts b/packages/payload/src/globals/config/types.ts
index a74a25d53..78fc9ce55 100644
--- a/packages/payload/src/globals/config/types.ts
+++ b/packages/payload/src/globals/config/types.ts
@@ -106,6 +106,8 @@ export type GlobalAdminOptions = {
       Edit?: EditConfig
     }
   }
+  /** Extension point to add your custom data. Available in server and client. */
+  custom?: Record<string, any>
   /**
    * Custom description for collection
    */
@@ -140,17 +142,8 @@ export type GlobalConfig = {
     update?: Access
   }
   admin?: GlobalAdminOptions
-  /** Extension point to add your custom data. */
-  custom?: {
-    /**
-     * Available in client bundle.
-     */
-    client?: Record<string, any>
-    /**
-     * Server only.
-     */
-    server?: Record<string, any>
-  }
+  /** Extension point to add your custom data. Server only. */
+  custom?: Record<string, any>
   /**
    * Customize the SQL table name
    */
diff --git a/packages/ui/src/fields/shared/index.tsx b/packages/ui/src/fields/shared/index.tsx
index a0d06e783..6df1efb22 100644
--- a/packages/ui/src/fields/shared/index.tsx
+++ b/packages/ui/src/fields/shared/index.tsx
@@ -17,9 +17,7 @@ export type FormFieldBase = {
   CustomError?: React.ReactNode
   CustomLabel?: React.ReactNode
   className?: string
-  custom?: {
-    client?: Record<string, any>
-  }
+  custom?: Record<string, any>
   descriptionProps?: FieldDescriptionProps
   disabled?: boolean
   docPreferences?: DocumentPreferences
diff --git a/packages/ui/src/forms/FieldPropsProvider/index.tsx b/packages/ui/src/forms/FieldPropsProvider/index.tsx
index 0d08d1833..2619ed5f4 100644
--- a/packages/ui/src/forms/FieldPropsProvider/index.tsx
+++ b/packages/ui/src/forms/FieldPropsProvider/index.tsx
@@ -5,9 +5,7 @@ import type { FieldPermissions } from 'payload/types'
 import React from 'react'
 
 export type FieldPropsContextType = {
-  custom?: {
-    client?: Record<string, any>
-  }
+  custom?: Record<any, string>
   indexPath?: string
   path: string
   permissions?: FieldPermissions
@@ -21,6 +19,7 @@ export type FieldPropsContextType = {
 
 const FieldPropsContext = React.createContext<FieldPropsContextType>({
   type: '' as keyof FieldTypes,
+  custom: {},
   indexPath: '',
   path: '',
   permissions: {} as FieldPermissions,
@@ -31,9 +30,7 @@ const FieldPropsContext = React.createContext<FieldPropsContextType>({
 
 export type Props = {
   children: React.ReactNode
-  custom?: {
-    client?: Record<string, any>
-  }
+  custom?: Record<any, string>
   indexPath?: string
   path: string
   permissions?: FieldPermissions
diff --git a/packages/ui/src/forms/RenderFields/RenderField.tsx b/packages/ui/src/forms/RenderFields/RenderField.tsx
index 2084a5078..8ea1a99df 100644
--- a/packages/ui/src/forms/RenderFields/RenderField.tsx
+++ b/packages/ui/src/forms/RenderFields/RenderField.tsx
@@ -17,9 +17,7 @@ import { FieldPropsProvider, useFieldProps } from '../FieldPropsProvider/index.j
 
 type Props = {
   CustomField: MappedField['CustomField']
-  custom?: {
-    client?: Record<string, any>
-  }
+  custom?: Record<any, string>
   disabled: boolean
   fieldComponentProps?: FieldComponentProps
   indexPath?: string
diff --git a/packages/ui/src/forms/RenderFields/index.tsx b/packages/ui/src/forms/RenderFields/index.tsx
index 49fcd83ba..6a9cf9360 100644
--- a/packages/ui/src/forms/RenderFields/index.tsx
+++ b/packages/ui/src/forms/RenderFields/index.tsx
@@ -60,6 +60,7 @@ export const RenderFields: React.FC<Props> = (props) => {
             const {
               type,
               CustomField,
+              custom,
               disabled,
               fieldComponentProps,
               fieldComponentProps: { readOnly },
@@ -71,7 +72,7 @@ export const RenderFields: React.FC<Props> = (props) => {
             return (
               <RenderField
                 CustomField={CustomField}
-                custom={f.custom}
+                custom={custom}
                 disabled={disabled}
                 fieldComponentProps={fieldComponentProps}
                 indexPath={indexPath !== undefined ? `${indexPath}.${fieldIndex}` : `${fieldIndex}`}
diff --git a/packages/ui/src/providers/ComponentMap/buildComponentMap/fields.tsx b/packages/ui/src/providers/ComponentMap/buildComponentMap/fields.tsx
index 210a82885..60a45250c 100644
--- a/packages/ui/src/providers/ComponentMap/buildComponentMap/fields.tsx
+++ b/packages/ui/src/providers/ComponentMap/buildComponentMap/fields.tsx
@@ -200,7 +200,7 @@ export const mapFields = (args: {
           CustomDescription,
           CustomError,
           CustomLabel,
-          custom: field.custom,
+          custom: 'admin' in field && 'custom' in field.admin ? field.admin?.custom : undefined,
           descriptionProps,
           disabled: 'admin' in field && 'disabled' in field.admin ? field.admin?.disabled : false,
           errorProps,
@@ -296,6 +296,7 @@ export const mapFields = (args: {
 
               const reducedBlock: ReducedBlock = {
                 slug: block.slug,
+                custom: block.admin?.custom,
                 fieldMap: blockFieldMap,
                 imageAltText: block.imageAltText,
                 imageURL: block.imageURL,
@@ -756,7 +757,7 @@ export const mapFields = (args: {
             <WithServerSideProps Component={CustomFieldComponent} {...fieldComponentProps} />
           ) : undefined,
           cellComponentProps,
-          custom: field.custom,
+          custom: field?.admin?.custom,
           disableBulkEdit:
             'admin' in field && 'disableBulkEdit' in field.admin && field.admin.disableBulkEdit,
           fieldComponentProps,
diff --git a/packages/ui/src/providers/ComponentMap/buildComponentMap/types.ts b/packages/ui/src/providers/ComponentMap/buildComponentMap/types.ts
index e857309e5..69c884141 100644
--- a/packages/ui/src/providers/ComponentMap/buildComponentMap/types.ts
+++ b/packages/ui/src/providers/ComponentMap/buildComponentMap/types.ts
@@ -35,6 +35,7 @@ export type MappedTab = {
 }
 
 export type ReducedBlock = {
+  custom?: Record<any, string>
   fieldMap: FieldMap
   imageAltText?: string
   imageURL?: string
@@ -68,9 +69,7 @@ export type MappedField = {
   CustomCell?: React.ReactNode
   CustomField?: React.ReactNode
   cellComponentProps: CellComponentProps
-  custom?: {
-    client?: Record<string, any>
-  }
+  custom?: Record<any, string>
   disableBulkEdit?: boolean
   disabled?: boolean
   fieldComponentProps: FieldComponentProps
diff --git a/test/config/config.ts b/test/config/config.ts
index c159990b0..4fca7bead 100644
--- a/test/config/config.ts
+++ b/test/config/config.ts
@@ -26,8 +26,7 @@ export default buildConfigWithDefaults({
           name: 'title',
           type: 'text',
           custom: {
-            client: { description: 'The title of this page' },
-            server: { description: 'The title of this page' },
+            description: 'The title of this page',
           },
         },
         {
@@ -47,20 +46,17 @@ export default buildConfigWithDefaults({
                 },
               ],
               custom: {
-                client: { description: 'The blockOne of this page' },
-                server: { description: 'The blockOne of this page' },
+                description: 'The blockOne of this page',
               },
             },
           ],
           custom: {
-            client: { description: 'The blocks of this page' },
-            server: { description: 'The blocks of this page' },
+            description: 'The blocks of this page',
           },
         },
       ],
       custom: {
-        client: { externalLink: 'https://foo.bar' },
-        server: { externalLink: 'https://foo.bar' },
+        externalLink: 'https://foo.bar',
       },
     },
   ],
@@ -83,12 +79,11 @@ export default buildConfigWithDefaults({
           name: 'title',
           type: 'text',
           custom: {
-            client: { description: 'The title of my global' },
-            server: { description: 'The title of my global' },
+            description: 'The title of my global',
           },
         },
       ],
-      custom: { client: { foo: 'bar' }, server: { foo: 'bar' } },
+      custom: { foo: 'bar' },
     },
   ],
   endpoints: [
@@ -101,7 +96,7 @@ export default buildConfigWithDefaults({
       custom: { description: 'Get the sanitized payload config' },
     },
   ],
-  custom: { client: { name: 'Customer portal' }, server: { name: 'Customer portal' } },
+  custom: { name: 'Customer portal' },
   onInit: async (payload) => {
     await payload.create({
       collection: 'users',
diff --git a/test/config/int.spec.ts b/test/config/int.spec.ts
index 8052922ac..b02acbd9a 100644
--- a/test/config/int.spec.ts
+++ b/test/config/int.spec.ts
@@ -21,8 +21,7 @@ describe('Config', () => {
     it('allows a custom field at the config root', () => {
       const { config } = payload
       expect(config.custom).toEqual({
-        client: { name: 'Customer portal' },
-        server: { name: 'Customer portal' },
+        name: 'Customer portal',
       })
     })
 
@@ -39,8 +38,7 @@ describe('Config', () => {
     it('allows a custom field in collections', () => {
       const [collection] = payload.config.collections
       expect(collection.custom).toEqual({
-        client: { externalLink: 'https://foo.bar' },
-        server: { externalLink: 'https://foo.bar' },
+        externalLink: 'https://foo.bar',
       })
     })
 
@@ -57,11 +55,8 @@ describe('Config', () => {
       const [collection] = payload.config.collections
       const [field] = collection.fields
 
-      console.log({ custom: field.custom })
-
       expect(field.custom).toEqual({
-        client: { description: 'The title of this page' },
-        server: { description: 'The title of this page' },
+        description: 'The title of this page',
       })
     })
 
@@ -70,8 +65,7 @@ describe('Config', () => {
       const [, blocksField] = collection.fields
 
       expect((blocksField as BlockField).blocks[0].custom).toEqual({
-        server: { description: 'The blockOne of this page' },
-        client: { description: 'The blockOne of this page' },
+        description: 'The blockOne of this page',
       })
     })
   })
@@ -79,7 +73,7 @@ describe('Config', () => {
   describe('global config', () => {
     it('allows a custom field in globals', () => {
       const [global] = payload.config.globals
-      expect(global.custom).toEqual({ client: { foo: 'bar' }, server: { foo: 'bar' } })
+      expect(global.custom).toEqual({ foo: 'bar' })
     })
 
     it('allows a custom field in global endpoints', () => {
@@ -94,8 +88,7 @@ describe('Config', () => {
       const [field] = global.fields
 
       expect(field.custom).toEqual({
-        client: { description: 'The title of my global' },
-        server: { description: 'The title of my global' },
+        description: 'The title of my global',
       })
     })
   })
diff --git a/test/fields/collections/UI/UICustomClient.tsx b/test/fields/collections/UI/UICustomClient.tsx
index 1e2757050..08a355d72 100644
--- a/test/fields/collections/UI/UICustomClient.tsx
+++ b/test/fields/collections/UI/UICustomClient.tsx
@@ -4,7 +4,6 @@ import React from 'react'
 
 export const UICustomClient: React.FC = () => {
   const { custom, path } = useFieldProps()
-  const client = custom?.client
 
-  return <div id={path}>{client?.customValue}</div>
+  return <div id={path}>{custom?.customValue}</div>
 }
diff --git a/test/fields/collections/UI/index.ts b/test/fields/collections/UI/index.ts
index 34d58a27e..95bd6dfc4 100644
--- a/test/fields/collections/UI/index.ts
+++ b/test/fields/collections/UI/index.ts
@@ -7,6 +7,12 @@ const UIFields: CollectionConfig = {
   slug: uiFieldsSlug,
   admin: {
     useAsTitle: 'text',
+    custom: {
+      'new-value': 'client available',
+    },
+  },
+  custom: {
+    'new-server-value': 'only available on server',
   },
   defaultSort: 'id',
   fields: [
@@ -22,13 +28,13 @@ const UIFields: CollectionConfig = {
         components: {
           Field: UICustomClient,
         },
-      },
-      custom: {
-        client: {
+        custom: {
           customValue: `client-side-configuration`,
         },
+      },
+      custom: {
         server: {
-          'new-server-value': 'only available on server',
+          serverOnly: 'string',
         },
       },
     },
diff --git a/test/fields/config.ts b/test/fields/config.ts
index 2316a83bc..1f459db68 100644
--- a/test/fields/config.ts
+++ b/test/fields/config.ts
@@ -82,6 +82,13 @@ export default buildConfigWithDefaults({
       'new-server-value': 'only available on server',
     },
   },
+  admin: {
+    custom: {
+      client: {
+        'new-value': 'client available',
+      },
+    },
+  },
   localization: {
     defaultLocale: 'en',
     fallback: true,