diff --git a/src/listeners/browser.ts b/src/listeners/browser.ts
index 0792c3a6..c99675bf 100644
--- a/src/listeners/browser.ts
+++ b/src/listeners/browser.ts
@@ -28,14 +28,14 @@ export class BrowserSignalListener implements ISignalListener {
   private serviceApi: ISplitApi;
   private fromImpressionsCollector: (data: SplitIO.ImpressionDTO[]) => ImpressionsPayload;
 
-  constructor({ syncManager, settings, storage, splitApi }: ISdkFactoryContextSync) {
+  constructor({ syncManager, settings, storage, splitApi, entityType }: ISdkFactoryContextSync) {
     this.syncManager = syncManager;
     this.settings = settings;
     this.storage = storage;
     this.serviceApi = splitApi;
     this.flushData = this.flushData.bind(this);
     this.flushDataIfHidden = this.flushDataIfHidden.bind(this);
-    this.fromImpressionsCollector = fromImpressionsCollector.bind(undefined, settings.core.labelsEnabled);
+    this.fromImpressionsCollector = fromImpressionsCollector.bind(undefined, settings.core.labelsEnabled, entityType);
   }
 
   /**
diff --git a/src/sdkFactory/types.ts b/src/sdkFactory/types.ts
index 2b822dd0..1ef00591 100644
--- a/src/sdkFactory/types.ts
+++ b/src/sdkFactory/types.ts
@@ -43,6 +43,9 @@ export interface IPlatform {
   SignalListener?: new (params: ISdkFactoryContext) => ISignalListener, // Used by BrowserSignalListener
 }
 
+// Definition type
+export type EntityType = 'config' | 'flag';
+
 export interface ISdkFactoryContext {
   platform: IPlatform,
   sdkReadinessManager: ISdkReadinessManager,
@@ -55,7 +58,8 @@ export interface ISdkFactoryContext {
   splitApi?: ISplitApi,
   syncManager?: ISyncManager,
   clients: Record<string, SplitIO.IBasicClient>,
-  fallbackCalculator: IFallbackCalculator
+  fallbackCalculator: IFallbackCalculator,
+  entityType?: EntityType
 }
 
 export interface ISdkFactoryContextSync extends ISdkFactoryContext {
diff --git a/src/sync/submitters/__tests__/impressionsSubmitter.spec.ts b/src/sync/submitters/__tests__/impressionsSubmitter.spec.ts
index 135abb2e..92c5f511 100644
--- a/src/sync/submitters/__tests__/impressionsSubmitter.spec.ts
+++ b/src/sync/submitters/__tests__/impressionsSubmitter.spec.ts
@@ -1,4 +1,4 @@
-import { impressionsSubmitterFactory } from '../impressionsSubmitter';
+import { fromImpressionsCollector, impressionsSubmitterFactory } from '../impressionsSubmitter';
 import { loggerMock } from '../../../logger/__tests__/sdkLogger.mock';
 import { ImpressionsCacheInMemory } from '../../../storages/inMemory/ImpressionsCacheInMemory';
 
@@ -96,3 +96,20 @@ describe('Impressions submitter', () => {
   });
 
 });
+
+describe('fromImpressionsCollector', () => {
+
+  test('includes entityType in payload when provided', () => {
+    const impressions = [imp1, imp2];
+    const result = fromImpressionsCollector(false, 'config', impressions);
+
+    expect(result).toEqual([{
+      f: 'someFeature',
+      i: [
+        { k: 'k1', t: 'someTreatment', m: 0, c: 123, et: 'config' },
+        { k: 'k2', t: 'someTreatment', m: 0, c: 123, et: 'config' },
+      ]
+    }]);
+  });
+
+});
diff --git a/src/sync/submitters/impressionsSubmitter.ts b/src/sync/submitters/impressionsSubmitter.ts
index 2fa85ab4..b756a34e 100644
--- a/src/sync/submitters/impressionsSubmitter.ts
+++ b/src/sync/submitters/impressionsSubmitter.ts
@@ -3,20 +3,20 @@ import SplitIO from '../../../types/splitio';
 import { submitterFactory } from './submitter';
 import { ImpressionsPayload } from './types';
 import { SUBMITTERS_PUSH_FULL_QUEUE } from '../../logger/constants';
-import { ISdkFactoryContextSync } from '../../sdkFactory/types';
+import { EntityType, ISdkFactoryContextSync } from '../../sdkFactory/types';
 
 /**
  * Converts `impressions` data from cache into request payload.
  */
-export function fromImpressionsCollector(sendLabels: boolean, data: SplitIO.ImpressionDTO[]): ImpressionsPayload {
+export function fromImpressionsCollector(sendLabels: boolean, entityType: EntityType | undefined, data: SplitIO.ImpressionDTO[]): ImpressionsPayload {
   let groupedByFeature = groupBy(data, 'feature');
   let dto: ImpressionsPayload = [];
 
   forOwn(groupedByFeature, (value, name) => {
     dto.push({
-      f: name, // Test Name
+      f: name, // Definition type
       i: value.map(entry => { // Key Impressions
-        const keyImpression = {
+        return {
           k: entry.keyName, // Key
           t: entry.treatment, // Treatment
           m: entry.time, // Timestamp
@@ -24,10 +24,9 @@ export function fromImpressionsCollector(sendLabels: boolean, data: SplitIO.Impr
           r: sendLabels ? entry.label : undefined, // Rule
           b: entry.bucketingKey, // Bucketing Key
           pt: entry.pt, // Previous time
-          properties: entry.properties // Properties
+          properties: entry.properties, // Properties
+          et: entityType, // Definition type
         };
-
-        return keyImpression;
       })
     });
   });
@@ -43,11 +42,12 @@ export function impressionsSubmitterFactory(params: ISdkFactoryContextSync) {
   const {
     settings: { log, scheduler: { impressionsRefreshRate }, core: { labelsEnabled } },
     splitApi: { postTestImpressionsBulk },
-    storage: { impressions }
+    storage: { impressions },
+    entityType
   } = params;
 
   // retry impressions only once.
-  const syncTask = submitterFactory(log, postTestImpressionsBulk, impressions, impressionsRefreshRate, fromImpressionsCollector.bind(undefined, labelsEnabled), 1);
+  const syncTask = submitterFactory(log, postTestImpressionsBulk, impressions, impressionsRefreshRate, fromImpressionsCollector.bind(undefined, labelsEnabled, entityType), 1);
 
   // register impressions submitter to be executed when impressions cache is full
   impressions.setOnFullQueueCb(() => {
diff --git a/src/sync/submitters/types.ts b/src/sync/submitters/types.ts
index 36a76c9b..c5c44381 100644
--- a/src/sync/submitters/types.ts
+++ b/src/sync/submitters/types.ts
@@ -2,6 +2,7 @@
 import { IMetadata } from '../../dtos/types';
 import SplitIO from '../../../types/splitio';
 import { ISyncTask } from '../types';
+import { EntityType } from '../../sdkFactory/types';
 
 type ImpressionPayload = {
   /** Matching Key */
@@ -20,6 +21,8 @@ type ImpressionPayload = {
   pt?: number;
   /** Stringified JSON object with properties */
   properties?: string;
+  /** Definition type */
+  et?: EntityType,
 };
 
 export type ImpressionsPayload = {