diff --git a/backend/pkg/messages/messages.go b/backend/pkg/messages/messages.go
index e778f812c..a96f98de8 100644
--- a/backend/pkg/messages/messages.go
+++ b/backend/pkg/messages/messages.go
@@ -1320,15 +1320,15 @@ func (msg *PerformanceTrack) TypeID() int {
 
 type StringDict struct {
 	message
-	Key   string
+	Key   uint64
 	Value string
 }
 
 func (msg *StringDict) Encode() []byte {
-	buf := make([]byte, 21+len(msg.Key)+len(msg.Value))
+	buf := make([]byte, 21+len(msg.Value))
 	buf[0] = 50
 	p := 1
-	p = WriteString(msg.Key, buf, p)
+	p = WriteUint(msg.Key, buf, p)
 	p = WriteString(msg.Value, buf, p)
 	return buf[:p]
 }
@@ -1343,18 +1343,18 @@ func (msg *StringDict) TypeID() int {
 
 type SetNodeAttributeDict struct {
 	message
-	ID    uint64
-	Name  string
-	Value string
+	ID       uint64
+	NameKey  uint64
+	ValueKey uint64
 }
 
 func (msg *SetNodeAttributeDict) Encode() []byte {
-	buf := make([]byte, 31+len(msg.Name)+len(msg.Value))
+	buf := make([]byte, 31)
 	buf[0] = 51
 	p := 1
 	p = WriteUint(msg.ID, buf, p)
-	p = WriteString(msg.Name, buf, p)
-	p = WriteString(msg.Value, buf, p)
+	p = WriteUint(msg.NameKey, buf, p)
+	p = WriteUint(msg.ValueKey, buf, p)
 	return buf[:p]
 }
 
diff --git a/backend/pkg/messages/read-message.go b/backend/pkg/messages/read-message.go
index 0531c7d1c..ecc00183f 100644
--- a/backend/pkg/messages/read-message.go
+++ b/backend/pkg/messages/read-message.go
@@ -795,7 +795,7 @@ func DecodePerformanceTrack(reader BytesReader) (Message, error) {
 func DecodeStringDict(reader BytesReader) (Message, error) {
 	var err error = nil
 	msg := &StringDict{}
-	if msg.Key, err = reader.ReadString(); err != nil {
+	if msg.Key, err = reader.ReadUint(); err != nil {
 		return nil, err
 	}
 	if msg.Value, err = reader.ReadString(); err != nil {
@@ -810,10 +810,10 @@ func DecodeSetNodeAttributeDict(reader BytesReader) (Message, error) {
 	if msg.ID, err = reader.ReadUint(); err != nil {
 		return nil, err
 	}
-	if msg.Name, err = reader.ReadString(); err != nil {
+	if msg.NameKey, err = reader.ReadUint(); err != nil {
 		return nil, err
 	}
-	if msg.Value, err = reader.ReadString(); err != nil {
+	if msg.ValueKey, err = reader.ReadUint(); err != nil {
 		return nil, err
 	}
 	return msg, err
diff --git a/ee/connectors/msgcodec/messages.py b/ee/connectors/msgcodec/messages.py
index 1df1b06a8..54f8df955 100644
--- a/ee/connectors/msgcodec/messages.py
+++ b/ee/connectors/msgcodec/messages.py
@@ -464,10 +464,10 @@ class StringDict(Message):
 class SetNodeAttributeDict(Message):
     __id__ = 51
 
-    def __init__(self, id, name, value):
+    def __init__(self, id, name_key, value_key):
         self.id = id
-        self.name = name
-        self.value = value
+        self.name_key = name_key
+        self.value_key = value_key
 
 
 class DOMDrop(Message):
diff --git a/ee/connectors/msgcodec/msgcodec.py b/ee/connectors/msgcodec/msgcodec.py
index 36d297998..0ba21ea12 100644
--- a/ee/connectors/msgcodec/msgcodec.py
+++ b/ee/connectors/msgcodec/msgcodec.py
@@ -433,15 +433,15 @@ class MessageCodec(Codec):
 
         if message_id == 50:
             return StringDict(
-                key=self.read_string(reader),
+                key=self.read_uint(reader),
                 value=self.read_string(reader)
             )
 
         if message_id == 51:
             return SetNodeAttributeDict(
                 id=self.read_uint(reader),
-                name=self.read_string(reader),
-                value=self.read_string(reader)
+                name_key=self.read_uint(reader),
+                value_key=self.read_uint(reader)
             )
 
         if message_id == 52:
diff --git a/frontend/app/player/web/managers/DOM/DOMManager.ts b/frontend/app/player/web/managers/DOM/DOMManager.ts
index 198c096ad..bb4c999ae 100644
--- a/frontend/app/player/web/managers/DOM/DOMManager.ts
+++ b/frontend/app/player/web/managers/DOM/DOMManager.ts
@@ -43,6 +43,7 @@ export default class DOMManager extends ListWalker<Message> {
   private activeIframeRoots: Map<number, number> = new Map()
   private styleSheets: Map<number, CSSStyleSheet> = new Map()
   private ppStyleSheets: Map<number, PostponedStyleSheet> = new Map()
+  private stringDict: Record<number,string> = {}
 
 
   private upperBodyId: number = -1;
@@ -134,6 +135,31 @@ export default class DOMManager extends ListWalker<Message> {
     parent.insertChildAt(child, index)
   }
 
+  private setNodeAttribute(msg: { id: number, name: string, value: string }) {
+    let { name, value } = msg;
+    const vn = this.vElements.get(msg.id)
+    if (!vn) { logger.error("Node not found", msg); return }
+    if (vn.node.tagName === "INPUT" && name === "name") {
+      // Otherwise binds local autocomplete values (maybe should ignore on the tracker level)
+      return
+    }
+    if (name === "href" && vn.node.tagName === "LINK") {
+      // @ts-ignore  ?global ENV type   // It've been done on backend (remove after testing in saas)
+      // if (value.startsWith(window.env.ASSETS_HOST || window.location.origin + '/assets')) {
+      //   value = value.replace("?", "%3F");
+      // }
+      if (!value.startsWith("http")) { return }
+      // blob:... value happened here. https://foss.openreplay.com/3/session/7013553567419137
+      // that resulted in that link being unable to load and having 4sec timeout in the below function.
+      this.stylesManager.setStyleHandlers(vn.node as HTMLLinkElement, value);
+    }
+    if (vn.node.namespaceURI === 'http://www.w3.org/2000/svg' && value.startsWith("url(")) {
+      value = "url(#" + (value.split("#")[1] ||")")
+    }
+    vn.setAttribute(name, value)
+    this.removeBodyScroll(msg.id, vn)
+  }
+
   private applyMessage = (msg: Message): Promise<any> | undefined => {
     let node: Node | undefined
     let vn: VNode | undefined
@@ -160,10 +186,11 @@ export default class DOMManager extends ListWalker<Message> {
         this.vRoots.clear()
         this.vRoots.set(0, vDoc) // watchout: id==0 for both Document and documentElement
         // this is done for the AdoptedCSS logic
-        // todo: start from 0 (sync logic with tracker)
+        // todo: start from 0-node (sync logic with tracker)
         this.vTexts.clear()
         this.stylesManager.reset()
         this.activeIframeRoots.clear()
+        this.stringDict = {}
         return
       case MType.CreateTextNode:
         vn = new VText()
@@ -200,28 +227,20 @@ export default class DOMManager extends ListWalker<Message> {
         vn.parentNode.removeChild(vn)
         return
       case MType.SetNodeAttribute:
-        let { name, value } = msg;
-        vn = this.vElements.get(msg.id)
-        if (!vn) { logger.error("Node not found", msg); return }
-        if (vn.node.tagName === "INPUT" && name === "name") {
-          // Otherwise binds local autocomplete values (maybe should ignore on the tracker level)
-          return
-        }
-        if (name === "href" && vn.node.tagName === "LINK") {
-          // @ts-ignore  ?global ENV type   // It've been done on backend (remove after testing in saas)
-          // if (value.startsWith(window.env.ASSETS_HOST || window.location.origin + '/assets')) {
-          //   value = value.replace("?", "%3F");
-          // }
-          if (!value.startsWith("http")) { return }
-          // blob:... value happened here. https://foss.openreplay.com/3/session/7013553567419137
-          // that resulted in that link being unable to load and having 4sec timeout in the below function.
-          this.stylesManager.setStyleHandlers(vn.node as HTMLLinkElement, value);
-        }
-        if (vn.node.namespaceURI === 'http://www.w3.org/2000/svg' && value.startsWith("url(")) {
-          value = "url(#" + (value.split("#")[1] ||")")
-        }
-        vn.setAttribute(name, value)
-        this.removeBodyScroll(msg.id, vn)
+        this.setNodeAttribute(msg)
+        return
+      case MType.StringDict:
+        this.stringDict[msg.key] = msg.value
+        return
+      case MType.SetNodeAttributeDict:
+        this.stringDict[msg.nameKey] === undefined && logger.error("No dictionary key for msg 'name': ", msg)
+        this.stringDict[msg.valueKey] === undefined && logger.error("No dictionary key for msg 'value': ", msg)
+        if (this.stringDict[msg.nameKey] === undefined || this.stringDict[msg.valueKey] === undefined ) { return }
+        this.setNodeAttribute({ 
+          id: msg.id,
+          name: this.stringDict[msg.nameKey],
+          value: this.stringDict[msg.valueKey],
+        })
         return
       case MType.RemoveNodeAttribute:
         vn = this.vElements.get(msg.id)
diff --git a/frontend/app/player/web/messages/RawMessageReader.gen.ts b/frontend/app/player/web/messages/RawMessageReader.gen.ts
index f76f9fb36..793f609f5 100644
--- a/frontend/app/player/web/messages/RawMessageReader.gen.ts
+++ b/frontend/app/player/web/messages/RawMessageReader.gen.ts
@@ -372,7 +372,7 @@ export default class RawMessageReader extends PrimitiveReader {
     }
 
     case 50: {
-      const key = this.readString(); if (key === null) { return resetPointer() }
+      const key = this.readUint(); if (key === null) { return resetPointer() }
       const value = this.readString(); if (value === null) { return resetPointer() }
       return {
         tp: MType.StringDict,
@@ -383,13 +383,13 @@ export default class RawMessageReader extends PrimitiveReader {
 
     case 51: {
       const id = this.readUint(); if (id === null) { return resetPointer() }
-      const name = this.readString(); if (name === null) { return resetPointer() }
-      const value = this.readString(); if (value === null) { return resetPointer() }
+      const nameKey = this.readUint(); if (nameKey === null) { return resetPointer() }
+      const valueKey = this.readUint(); if (valueKey === null) { return resetPointer() }
       return {
         tp: MType.SetNodeAttributeDict,
         id,
-        name,
-        value,
+        nameKey,
+        valueKey,
       };
     }
 
diff --git a/frontend/app/player/web/messages/raw.gen.ts b/frontend/app/player/web/messages/raw.gen.ts
index 517bdc834..b51edb40e 100644
--- a/frontend/app/player/web/messages/raw.gen.ts
+++ b/frontend/app/player/web/messages/raw.gen.ts
@@ -271,15 +271,15 @@ export interface RawPerformanceTrack {
 
 export interface RawStringDict {
   tp: MType.StringDict,
-  key: string,
+  key: number,
   value: string,
 }
 
 export interface RawSetNodeAttributeDict {
   tp: MType.SetNodeAttributeDict,
   id: number,
-  name: string,
-  value: string,
+  nameKey: number,
+  valueKey: number,
 }
 
 export interface RawResourceTiming {
diff --git a/frontend/app/player/web/messages/tracker.gen.ts b/frontend/app/player/web/messages/tracker.gen.ts
index 220c4f3da..2c171011c 100644
--- a/frontend/app/player/web/messages/tracker.gen.ts
+++ b/frontend/app/player/web/messages/tracker.gen.ts
@@ -260,15 +260,15 @@ type TrPerformanceTrack = [
 
 type TrStringDict = [
   type: 50,
-  key: string,
+  key: number,
   value: string,
 ]
 
 type TrSetNodeAttributeDict = [
   type: 51,
   id: number,
-  name: string,
-  value: string,
+  nameKey: number,
+  valueKey: number,
 ]
 
 type TrResourceTiming = [
@@ -705,8 +705,8 @@ export default function translate(tMsg: TrackerMessage): RawMessage | null {
       return {
         tp: MType.SetNodeAttributeDict,
         id: tMsg[1],
-        name: tMsg[2],
-        value: tMsg[3],
+        nameKey: tMsg[2],
+        valueKey: tMsg[3],
       }
     }
     
diff --git a/mobs/messages.rb b/mobs/messages.rb
index ab1b29c00..ef36ebfa7 100644
--- a/mobs/messages.rb
+++ b/mobs/messages.rb
@@ -279,14 +279,14 @@ message 49, 'PerformanceTrack' do  #, :replayer => :devtools --> requires player
 end
 # since 4.1.9
 message 50, "StringDict" do
-  string "Key"
+  uint "Key"
   string "Value"
 end
 # since 4.1.9
 message 51, "SetNodeAttributeDict" do
   uint 'ID'
-  string 'Name'
-  string 'Value'
+  uint 'NameKey'
+  uint 'ValueKey'
 end
 
 ## 50,51
diff --git a/tracker/tracker/src/common/messages.gen.ts b/tracker/tracker/src/common/messages.gen.ts
index 66a1c5c7b..8f61ab917 100644
--- a/tracker/tracker/src/common/messages.gen.ts
+++ b/tracker/tracker/src/common/messages.gen.ts
@@ -321,15 +321,15 @@ export type PerformanceTrack = [
 
 export type StringDict = [
   /*type:*/ Type.StringDict,
-  /*key:*/ string,
+  /*key:*/ number,
   /*value:*/ string,
 ]
 
 export type SetNodeAttributeDict = [
   /*type:*/ Type.SetNodeAttributeDict,
   /*id:*/ number,
-  /*name:*/ string,
-  /*value:*/ string,
+  /*nameKey:*/ number,
+  /*valueKey:*/ number,
 ]
 
 export type ResourceTiming = [
diff --git a/tracker/tracker/src/main/app/messages.gen.ts b/tracker/tracker/src/main/app/messages.gen.ts
index d3a7c3b08..bdec57a0f 100644
--- a/tracker/tracker/src/main/app/messages.gen.ts
+++ b/tracker/tracker/src/main/app/messages.gen.ts
@@ -475,7 +475,7 @@ export function PerformanceTrack(
 }
 
 export function StringDict(
-  key: string,
+  key: number,
   value: string,
 ): Messages.StringDict {
   return [
@@ -487,14 +487,14 @@ export function StringDict(
 
 export function SetNodeAttributeDict(
   id: number,
-  name: string,
-  value: string,
+  nameKey: number,
+  valueKey: number,
 ): Messages.SetNodeAttributeDict {
   return [
     Messages.Type.SetNodeAttributeDict,
     id,
-    name,
-    value,
+    nameKey,
+    valueKey,
   ]
 }
 
diff --git a/tracker/tracker/src/webworker/BatchWriter.ts b/tracker/tracker/src/webworker/BatchWriter.ts
index 167c1aff6..d9275ada3 100644
--- a/tracker/tracker/src/webworker/BatchWriter.ts
+++ b/tracker/tracker/src/webworker/BatchWriter.ts
@@ -1,6 +1,7 @@
 import type Message from '../common/messages.gen.js'
 import * as Messages from '../common/messages.gen.js'
 import MessageEncoder from './MessageEncoder.gen.js'
+import StringDictionary from './StringDictionary.js'
 
 const SIZE_BYTES = 3
 const MAX_M_SIZE = (1 << (SIZE_BYTES * 8)) - 1
@@ -9,6 +10,7 @@ export default class BatchWriter {
   private nextIndex = 0
   private beaconSize = 2 * 1e5 // Default 200kB
   private encoder = new MessageEncoder(this.beaconSize)
+  private strDict = new StringDictionary()
   private readonly sizeBuffer = new Uint8Array(SIZE_BYTES)
   private isEmpty = true
 
@@ -84,6 +86,14 @@ export default class BatchWriter {
     this.beaconSizeLimit = limit
   }
 
+  private applyDict(str: string): number {
+    const [key, isNew] = this.strDict.getKey(str)
+    if (isNew) {
+      this.writeMessage([Messages.Type.StringDict, key, str])
+    }
+    return key
+  }
+
   writeMessage(message: Message) {
     if (message[0] === Messages.Type.Timestamp) {
       this.timestamp = message[1] // .timestamp
@@ -91,6 +101,14 @@ export default class BatchWriter {
     if (message[0] === Messages.Type.SetPageLocation) {
       this.url = message[1] // .url
     }
+    if (message[0] === Messages.Type.SetNodeAttribute) {
+      message = [
+        Messages.Type.SetNodeAttributeDict,
+        message[1],
+        this.applyDict(message[2]),
+        this.applyDict(message[3]),
+      ] as Messages.SetNodeAttributeDict
+    }
     if (this.writeWithSize(message)) {
       return
     }
diff --git a/tracker/tracker/src/webworker/MessageEncoder.gen.ts b/tracker/tracker/src/webworker/MessageEncoder.gen.ts
index 5bd3f6a01..e6e522dd4 100644
--- a/tracker/tracker/src/webworker/MessageEncoder.gen.ts
+++ b/tracker/tracker/src/webworker/MessageEncoder.gen.ts
@@ -159,11 +159,11 @@ export default class MessageEncoder extends PrimitiveEncoder {
     break
 
     case Messages.Type.StringDict:
-      return  this.string(msg[1]) && this.string(msg[2])
+      return  this.uint(msg[1]) && this.string(msg[2])
     break
 
     case Messages.Type.SetNodeAttributeDict:
-      return  this.uint(msg[1]) && this.string(msg[2]) && this.string(msg[3])
+      return  this.uint(msg[1]) && this.uint(msg[2]) && this.uint(msg[3])
     break
 
     case Messages.Type.ResourceTiming:
diff --git a/tracker/tracker/src/webworker/StringDictionary.ts b/tracker/tracker/src/webworker/StringDictionary.ts
new file mode 100644
index 000000000..b183ce862
--- /dev/null
+++ b/tracker/tracker/src/webworker/StringDictionary.ts
@@ -0,0 +1,13 @@
+export default class StringDictionary {
+  private idx = 1
+  private backDict: Record<string, number> = {}
+
+  getKey(str: string): [number, boolean] {
+    let isNew = false
+    if (!this.backDict[str]) {
+      isNew = true
+      this.backDict[str] = this.idx++
+    }
+    return [this.backDict[str], isNew]
+  }
+}
diff --git a/tracker/tracker/src/webworker/StringDictionary.unit.test.ts b/tracker/tracker/src/webworker/StringDictionary.unit.test.ts
new file mode 100644
index 000000000..8bf17e14b
--- /dev/null
+++ b/tracker/tracker/src/webworker/StringDictionary.unit.test.ts
@@ -0,0 +1,33 @@
+import { describe, expect, test, jest, beforeEach, afterEach } from '@jest/globals'
+import StringDictionary from './StringDictionary.js'
+
+describe('StringDictionary', () => {
+  test('key is non-zero', () => {
+    const dict = new StringDictionary()
+
+    const [key, isNew] = dict.getKey('We are Asayer')
+
+    expect(key).not.toBe(0)
+    expect(isNew).toBe(true)
+  })
+
+  test('Different strings have different keys', () => {
+    const dict = new StringDictionary()
+
+    const [key1, isNew1] = dict.getKey('Datadog')
+    const [key2, isNew2] = dict.getKey('PostHog')
+
+    expect(key1).not.toBe(key2)
+    expect(isNew2).toBe(true)
+  })
+
+  test('Similar strings have similar keys', () => {
+    const dict = new StringDictionary()
+
+    const [key1, isNew1] = dict.getKey("What's up?")
+    const [key2, isNew2] = dict.getKey("What's up?")
+
+    expect(key1).toBe(key2)
+    expect(isNew2).toBe(false)
+  })
+})