Firestore errorFirestore: “Function addDoc() called with invalid data. Unsupported field value: undefined”

Rather not fix it yourself? App Fix Ticket starts with a fixed-price diagnosis, then a fixed price for the fix before any fix work.

Why the field is undefined, and the fix

1. 01

   An optional field has no value

   “If set to false or omitted, the SDK throws an exception when it encounters properties of type undefined.” Firebase, FirestoreSettings.ignoreUndefinedProperties

   One undefined field makes the SDK refuse the whole write. setDoc and updateDoc refuse it the same way. In the Admin SDK the message reads “Cannot use undefined as a Firestore value”.

2. 02

   Leave out empty fields before saving

   Strip undefined values from the object, or set the ones you want stored to null. This helper handles top-level fields only, so clean nested objects too if you have them.

   const clean = Object.fromEntries(
     Object.entries(data).filter(([, v]) => v !== undefined),
   );
   await addDoc(collection(db, 'orders'), clean);

3. 03

   Let the SDK skip them

   “If set to true, these properties are skipped and not written to Firestore.” Firebase, FirestoreSettings.ignoreUndefinedProperties

   Set the option once, before any other Firestore call, or initializeFirestore throws because Firestore already started. Test it with your data shape, since undefined values inside arrays may not be skipped.

   import { initializeFirestore } from 'firebase/firestore';
   
   const db = initializeFirestore(app, { ignoreUndefinedProperties: true });
   
   // Admin SDK (Node), before the first read or write
   // import { getFirestore } from 'firebase-admin/firestore';
   // getFirestore().settings({ ignoreUndefinedProperties: true });

4. 04

   The value really should be there

   If the field must exist, skipping it hides a bug. Check the source: a typo in a property name, a value read before it loaded, or an API response missing a key.

Checked against the vendor’s docs on November 9, 2026: Firebase reference: FirestoreSettings.

Rather hand it over?

Fixed scope, fixed price, paid upfront. The work happens in writing; no call needed.

• from $450App Fix TicketOne reproducible bug in an existing mobile or web app, diagnosed and fixed.See scope and start
• from $450AI-Built App RescueA Lovable, Bolt or Cursor app checked end to end in 3 days, then its worst problems fixed at a fixed price.No issues worth fixing, no charge. If the Launch Check finds nothing rated medium or higher, Simon refunds the full $450. You keep the report either way. This applies to the first 10 Launch Checks bought after October 30, 2026.See scope and start

Related: Firestore ALREADY_EXISTS · Firebase “Missing or insufficient permissions” · Firestore query requires an index · Firebase Storage object-not-found