diff --git a/src/shared/board.ts b/src/shared/board.ts
index 76afbf2..1d5f6d7 100644
--- a/src/shared/board.ts
+++ b/src/shared/board.ts
@@ -3,7 +3,10 @@ import { BoardType, SquareState, formatSquareState, parseSquareState } from "./d
 
 export class Board implements BoardType {
   // State should be immutable
-  constructor(private readonly state: SquareState[][]) {}
+  constructor(
+    private readonly state: SquareState[][],
+    private serialized?: string,
+  ) {}
 
   hasRow(row: number) {
     return !!this.state[row];
@@ -53,10 +56,11 @@ export class Board implements BoardType {
           return squareState;
         }),
       ),
+      serialized,
     );
   }
 
-  serialize() {
+  private forceSerialize() {
     return this.state
       .map((row) =>
         row
@@ -72,4 +76,13 @@ export class Board implements BoardType {
       )
       .join("|");
   }
+
+  serialize() {
+    if (!this.serialized) {
+      const serialized = this.forceSerialize();
+      this.serialized = serialized;
+    }
+
+    return this.serialized;
+  }
 }