Firestore Emulator Bug: Data Writes Succeed But Nothing Shows Up (Solved)

🧪 What Happened

The Setup

• Used a single Firebase project for both production and development
• Ran Firestore locally with the Emulator Suite
• Used local-only mode to avoid writing to production
• Everything worked: writes, reads, rules, etc.

⚐️ The Shift

• Split Firebase into:

  • A production project
  • A separate dev project for local testing

Motivation: Emulator Suite doesn’t support everything; separation avoids conflicts with production

😤 The Problem

• Firestore writes succeeded:

  • ✅ Green checks in Emulator UI Requests tab
  • ✅ No rule violations

• But Firestore Data tab was empty:

  • No /users, /words, or new documents

Yet logs showed:

create /databases/(default)/documents/users/UID/words/term|lang
update /databases/(default)/documents/users/UID/words/term|lang

Diagnosis

🔍 The Root Cause

• Emulator UI only shows the Firestore DB for the default project set in Firebase CLI

• If CLI context is set to a different (old) project:

  • Emulator writes go to one DB
  • UI reads from another
  • ❌ Data mismatch

The Fix: Set the Correct Default Project

✅ Step-by-step

1. Open terminal in your project folder

2. Add a project alias:

   firebase use --add
   

3. Enter an alias (e.g., dev)

4. Set it as default:

   firebase use dev
   

5. Restart the emulator:

   firebase emulators:start
   

Now UI shows the correct database: /firestore/data/databases/(default)/documents

🔧 Optional: Set Default in .firebaserc

Update .firebaserc:

{
  "projects": {
    "default": "your-dev-project-id"
  }
}

Prevents accidental CLI context mismatch.

Conclusion

If writes succeed but no data appears:

• You’re likely writing to one project while UI reads another

Solution

firebase use <project-alias>
firebase emulators:start

🤀 TL;DR

Happy emulating 👨‍💻🔥