Stack
Firebase
Google's app backend built around the Firestore document database, with auth, hosting, functions, and push notifications included.
What it actually does
Firebase is Google's backend-as-a-service centered on Firestore, a NoSQL document database, with authentication, static hosting, Cloud Functions, and Firebase Cloud Messaging for push notifications. Its client SDKs handle offline caching and sync, which is why it is common in mobile apps.
The free Spark tier has quotas that never pause, so a low-traffic app can sit at exactly $0 indefinitely, and 50K free auth monthly active users plus free push notifications replace separate paid tools. To deploy Cloud Functions at all you must upgrade to the pay-as-you-go Blaze plan with a card on file.
The cost risk is the billing model: Firestore charges per document read and write, so a chatty listener or an unoptimized query can multiply your bill quietly, and Blaze has no hard spend cap. Budget alerts notify you but do not stop the meter.
Firebase vs its main rivals
The tools people actually weigh against Firebase: Supabase, AWS Amplify, Appwrite. Same criteria for every column, including where Firebase loses.
| Firebase |  Supabase |  AWS Amplify |  Appwrite | |
|---|---|---|---|---|
Pricing & access | ||||
| Free tier | Unknown1 GiB, no pause | Unknown500 MB | Unknown12-mo AWS free | Unknown2 GB |
| Starting price | $0 PAYG | $25/mo | $0 PAYG | $25/mo |
| Free tier never pauses | YesYes | NoPauses 7d | YesYes | YesYes |
Database engine | ||||
| Relational SQL / Postgres | NoNoSQL | YesPostgres | UnknownAurora opt. | NoDocument |
| Offline mobile sync SDK | YesYes | UnknownLimited | YesDataStore | UnknownPartial |
Cost safety | ||||
| Hard spend cap | NoNo cap | YesSpend cap | NoNo cap | UnknownPlan cap |
| Usage billing model | Per op | Flat+overage | Per resource | Flat+usage |
Bundled services | ||||
| Built-in auth | 50K free | Free | Free | 75K free |
| Push notifications | YesFCM free | NoNo | UnknownSNS | YesYes |
Developer & API | ||||
| Serverless functions | Blaze only | Free | Free | Free |
Portability | ||||
| Self-host / open source | NoNo | YesYes | NoNo | YesYes |
- Free Spark quotas never pause, so a low-traffic app can run at exactly $0 indefinitely
- 50K free auth monthly active users plus free push notifications replace separate paid auth and messaging tools
- Mature mobile SDKs with offline sync, well suited to apps that ship as iOS or Android clients
- Firestore bills per document operation, so an unoptimized query or chatty listener can multiply the bill quietly
- Blaze has no hard spend cap; budget alerts notify but do not stop the meter
- NoSQL document model means no relational joins, so relational apps fit awkwardly
Pay less for it
5 ways foundThe free tier never pauses; a low-traffic app can run at $0 as long as you do not need Cloud Functions
Eligible new Blaze users get $300 in Google Cloud credit to offset early usage
Alerts do not cap spend but give early warning before a runaway Firestore bill grows
Caching and narrower queries directly cut the per-operation bill, often the single biggest lever
Supabase — If you want relational data and a hard spend cap instead of per-operation billing, Supabase's flat $25 Pro is more predictable
StackTracker tracks what you actually pay for Firebase and every other tool, flags overpayment, and shows the dollars you would save by switching.
Is it the right tool for you
- You are shipping a mobile-first app and want offline sync out of the box
- You want a true $0 idle cost and will keep read patterns disciplined
- You want free push notifications and auth bundled in
- Your data is relational and needs joins → use Supabase
- You want a hard cap that guarantees the bill cannot run away → use MongoDB Atlas
Track what Firebase and the rest of your stack cost
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Prices and limits last verified 2026-07-20.