diff --git a/schema/firebase-config.json b/schema/firebase-config.json
index 546d045af00..2e1bdc141e1 100644
--- a/schema/firebase-config.json
+++ b/schema/firebase-config.json
@@ -1194,6 +1194,9 @@
                     },
                     "type": "object"
                 },
+                "dataDir": {
+                    "type": "string"
+                },
                 "database": {
                     "additionalProperties": false,
                     "properties": {
diff --git a/src/command.ts b/src/command.ts
index 325654c7953..627e04bf82d 100644
--- a/src/command.ts
+++ b/src/command.ts
@@ -100,6 +100,18 @@ export class Command {
     return this;
   }
 
+  /**
+   * Adds the --ephemeral flag to the command.
+   * @return The command, for chaining.
+   */
+  withEphemeral(): Command {
+    this.option(
+      "--ephemeral",
+      "ignore emulators.dataDir and start with a clean state",
+      false, // Default value if the flag is not present
+    );
+    return this;
+  }
   /**
    * Attaches a function to run before the command's action function.
    * @param fn the function to run.
diff --git a/src/commands/emulators-exec.ts b/src/commands/emulators-exec.ts
index dadd455bd3a..e11ca60930f 100644
--- a/src/commands/emulators-exec.ts
+++ b/src/commands/emulators-exec.ts
@@ -8,6 +8,7 @@ export const command = new Command("emulators:exec <script>")
   .description(
     "start the local Firebase emulators, run a test script, then shut down the emulators",
   )
+  .withEphemeral()
   .option(commandUtils.FLAG_ONLY, commandUtils.DESC_ONLY)
   .option(commandUtils.FLAG_INSPECT_FUNCTIONS, commandUtils.DESC_INSPECT_FUNCTIONS)
   .option(commandUtils.FLAG_IMPORT, commandUtils.DESC_IMPORT)
diff --git a/src/commands/emulators-start.ts b/src/commands/emulators-start.ts
index 6ddc4f3d135..1b877c55b87 100644
--- a/src/commands/emulators-start.ts
+++ b/src/commands/emulators-start.ts
@@ -20,6 +20,7 @@ export const command = new Command("emulators:start")
   .before(commandUtils.setExportOnExitOptions)
   .before(commandUtils.beforeEmulatorCommand)
   .description("start the local Firebase emulators")
+  .withEphemeral()
   .option(commandUtils.FLAG_ONLY, commandUtils.DESC_ONLY)
   .option(commandUtils.FLAG_INSPECT_FUNCTIONS, commandUtils.DESC_INSPECT_FUNCTIONS)
   .option(commandUtils.FLAG_IMPORT, commandUtils.DESC_IMPORT)
diff --git a/src/firebaseConfig.ts b/src/firebaseConfig.ts
index b0c46bee651..c5eed5dcbc1 100644
--- a/src/firebaseConfig.ts
+++ b/src/firebaseConfig.ts
@@ -252,6 +252,7 @@ export type EmulatorsConfig = {
     host?: string;
     port?: number;
   };
+  dataDir?: string;
 };
 
 export type ExtensionsConfig = Record<string, string>;