Supabase vs Firebase Cost Comparison 2026: Free Limits and Project-Specific Selection Criteria

1. One-line problem definition: It is a problem of choosing an axis that increases cost, not a cheap backend

Key line: The price lists of Supabase and Firebase do not compare the same units, so it is easy to make the wrong choice by only looking at the monthly basic fee.

Supabase charges based on PostgreSQL compute and organizational unit usage, while Firestore, Firebase's representative database, charges based on document read/write/delete and network usage. Therefore, the question “How much is 10,000 users?” can be answered by including the number of queries per screen, real-time listeners, file transfer volume, and data relationships.

This article helps you choose web SaaS, mobile apps, and admin tools based on the official pricing page as of July 2026. This is not an article that provides a definitive estimate for additional services such as taxes, exchange rates, and Cloud Functions for a specific region. Before making the actual payment, you must check again with each company's calculator.

2. First, conclusion: Supabase is advantageous for relational web SaaS, and Firebase is advantageous for offline mobile

Key line: If data relationships and SQL are key, consider Supabase first. If mobile offline synchronization and Google ecosystem are key, consider Firebase first.

• Supabase Recommended for: Teams where SaaS with many joins, such as customers, organizations, subscriptions, and orders, SQL reports, row-level permissions, and cost predictability are important.
• Firebase Recommendation: Mobile products where real-time synchronization and offline reconnection are important, such as chat, feed, and field apps, and a team that uses Crashlytics, FCM, and Google Analytics in one ecosystem.
• If both are too much: For read-oriented simple content sites, static generation and lightweight hosting are cheaper and simpler.

If you look at the free section, both are strong. Supabase Free provides 500MB of database, 1GB of storage, 50,000 monthly active users, and 5GB of transmission per project. Firebase Spark's Firestore provides 50,000 document reads, 20,000 writes, and 20,000 document deletions per day, and Firebase Authentication is free for up to 50,000 monthly active users. However, since the free limit units are mixed into month, day, and project, the numbers should not be interpreted as superiority or inferiority.

3. Decomposition of core structure: data·authentication·file·function four bills

Key line: BaaS costs are the result of four usage axes combined, not just one database.

1. Data Layer: Supabase focuses on PostgreSQL compute and disk in one project. Firebase Firestore is focused on the number of document operations, and reading index entries in queries can also affect billing.
2. Authentication Tier: For both services, regular authentication looks at the number of monthly active users. For enterprise functions such as phone authentication and SAML/OIDC, separate prices and conditions must be checked.
3. File/Network Layer: For images and videos, the download volume can increase costs faster than the storage capacity. CDN cache must also be measured.
4. Execution Layer: Edge Functions or Cloud Functions view invocation, execution time, memory and external network separately. Even if the database is free, it doesn't mean the function is free.

If the cost model is simplified to the equation, it is Monthly cost = base compute + excess storage + excess egress + excess authentication + function execution + data operations. In Supabase, the proportion of fixed costs in the front is relatively large, and in Firestore, the proportion of variable costs in the last data operation is relatively large.

4. Explanation of design intent: Exchange of fixed capacity and pay-as-you-go usage

Key line: Supabase is closer to the sense of renting a server, and Firestore is closer to the sense of buying an API call.

The reason Supabase focuses on PostgreSQL is to process relationships, transactions, SQL, and Row Level Security in one data engine. Instead of being able to bundle complex queries into a single SQL and tune the execution plan and indexes, the compute costs of paid projects exist even when there is little traffic.

Firestore prioritizes document-level distribution and client synchronization. While it is easy for the SDK to directly subscribe to and auto-extend the necessary documents, costs can grow faster than the number of users when screen re-rendering or a poorly designed real-time listener repeatedly reads the document. In other words, Supabase requires capacity planning and SQL operation capabilities, and Firebase requires access patterns and number of operations design.

Firebase Data Connect provides Cloud SQL for PostgreSQL, undermining the old comparison that “Firebase is only NoSQL.” According to the official pricing page, after a 3-month free trial, depending on the configuration, you can start at $9.37 per month. However, this is a different billing structure from Firestore, so if you choose Data Connect, you must compare it again based on Supabase and relational databases.

5. Evidence and comparison: Look at the unit price and operating method in excess of free

Key line: “What action creates the next dollar” is a more important comparison standard than the initial 0 won.

Judgment criteria	Supabase	Firebase/Firestore	Practical interpretation
Free Data	DB 500MB/project	Storage 1GiB	Due to relational schema and document structure, simple capacity comparison is prohibited
Free Certification	50,000 MAU per month	50,000 MAU per month	Check phone and corporate authentication separately
Free to read/write	Focus on DB resources rather than number of API requests	Read 50,000/day, write/delete 20,000/day each	For Firestore, the number of document reads per screen is key
Paid entry	Pro organization subscription and project compute, Pro starting at $25 based on official comparison table	Blaze pay-as-you-go	Firebase can be convenient for low usage, and Supabase can be convenient for predictability
Example of Pro inclusion amount	DB 8GB/project, storage 100GB, transmission 250GB, 100,000 MAU	Free section by service/region, then pay as you go	Firebase requires calculator input
Data Model	PostgreSQL, SQL, join, transaction	Firestore document or Data Connect PostgreSQL	Fix the requirements first
Offline Mobile	Direct supplementation required	Mature SDK cache/synchronization	On-site apps have a significant effect of reducing development costs
Exit path	Postgres dump·Self-hosting available	Google managed service focus	Migration cost is also included in the total cost

The Supabase official document describes Pro's excess usage as $0.125 per GB of database disk, $0.021 per GB of storage, $0.09 per GB of transmission, and $0.00325 per MAU exceeding 100,000 users. Firebase unit prices vary depending on region and service, so you must use the Firestore price list and Blaze calculator. Since prices may change, the numbers in this article are the starting point for quotations and not the contract amount.

6. Real-world operational flow: 20-minute cost simulation

Key line: If you count reading, writing, and sending of three representative screens instead of the number of users, the estimate error is greatly reduced.

1. Choose a representative action. Write down three actions that generate 80% of traffic, such as logging in, opening the dashboard, or creating an order.
2. Counts data operations per action. If the dashboard reads 1 customer, 20 orders, and 10 notifications as separate documents, it can be read up to 31 times at a time. The actual value varies depending on the cache and query results.
3. Calculate monthly usage.Use Reads per action × Users per day × Runs per user × 30 as the basic formula.
4. Separate the transmission volume. If you upload a thumbnail of 300 KB 100,000 times a month, it is about 30 GB. If you send the original image as is, the network becomes a cost bottleneck before the database.
5. Insert the same assumptions into both calculators. Subtract the free limit and compare the normal month, 3 times the event month, and 10 times the faulty retry month.

Example assumptions
DAU: 1,000
Dashboard: 3 times per day per user
Firestore document reads: 25 times per screen
Reads per month: 1,000 × 3 × 25 × 30 = 2,250,000
Image transmission: 0.3MB × 100,000 times ≈ 30GB

Things to verify: cache hit rate, real-time reconnects, duplicate queries, regional unit cost

If testing

Supabase, verify the schema and RLS policy locally with supabase start, and if testing Firebase, check the number of reads and Security Rules in the Emulator Suite. Before operation, assumed values ​​must be replaced with actual SDK measurements.

7. Mistake/Trap: Pattern of relying on free limits and slowing operational instrumentation

Key line: Cost accidents usually happen not because the price is high, but when you don't know what code created the usage.

Trip 1. Firestore real-time listener is not separated from the screen life cycle

Duplicate subscriptions and reconnections can increase reads. Test unsubscription and record the number of concurrent listeners per screen in the dashboard. If the cost jumps, narrow down and restore only the fields that really need real-time.

Trap 2. Misunderstand the anon key as secure without Supabase RLS

The public key itself is not a security boundary. Turn on RLS for all exposure tables and write user and organization boundary tests. If the possibility of a leak is confirmed, the policy is blocked first and the service role key log is rotated.

Trap 3. Subtract the number of development/staging projects from the estimate

Compute for Supabase paid projects, additional Firebase databases, and Cloud SQL costs may increase depending on the number of environments. Set the retention period for operation, staging, and PR previews and automatically terminate them.

Trap 4. Repeatedly download the original file directly from the app

If there is no image resize or cache header, the transmission volume increases rapidly. Set the thumbnail pipeline, CDN cache, and maximum upload size first.

Trap 5. Not testing the conditions for moving from a free plan to a paid plan

The available services and billing methods may change the moment you connect your payment account. Don't just rely on budget notifications, prepare for daily usage limits, abnormal call blocking, and app degradation modes.

8. Strengths and limitations: Development speed is also a total cost of ownership

Key line: The labor cost of running an unfamiliar permissions model for your team can be greater than the $10 difference in infrastructure billing.

Supabase's strengths are standard PostgreSQL, SQL migration, complex relational queries, and data portability. Conversely, if no one understands indexes, connections, slow queries, and RLS, it creates a management burden. A disadvantage of a one-person MVP is that fixed costs are incurred even at low usage when moving from free to Pro.

Firebase's strengths include mobile SDK, offline synchronization, auto-scaling, and Google product integration. Conversely, forcing relational requirements into the document model increases data duplication, fan-out writes, read costs, and migration costs. Conclusions like Firestore is always cheaper or Supabase is always predictable are both wrong.

If relational is required but BaaS functionality is at least possible, serverless Postgres such as Neon can also be compared. If global edge reads and distributed SQL are key, another database may be right. The options are not closed to two services.

9. Points to study more deeply and internal learning path

Key line: After the price list, you need to study permissions, queries, and observability to control the actual cost.

Please refer to

• Supabase official price list and Supabase official charging structure document for the latest inclusion amount and organizational unit summation method. Check.
Read listener, index entry, and free database conditions from
• Firebase official price list and Cloud Firestore official billing document.
• To see more comparison articles, check the same cost simulation method in n8n·Make·Zapier cost comparison.
• Step-by-step AI/development guide can be viewed in AQ Guide Hub.
• Before selecting the tool, check your level of AI utilization with AQ Test and select the appropriate learning path.

10. Action Checklist + Author's Perspective

Key line: Choose the one that passes 10x the traffic and churn scenario, not the one-month free demo.

• Have you measured three representative user actions and the number of reads and writes per action?
• Have you calculated the monthly cost of normal, 3x, and 10x traffic using the same assumption?
• Have you calculated the image/file transmission volume and cache hit rate separately?
• Did you include the number of projects in production, staging, and preview environments?
• Have you automatically tested Supabase RLS or Firebase Security Rules?
• Have you verified duplicate requests when unsubscribing in real time and reconnecting offline?
• Have you set up budget alerts, daily usage observation, and abnormal call blocking?
• Have you actually timed data export and recovery to another provider?

Definition of Done: Calculate the normal/triple traffic cost for both services using the actual measurement values of the representative screen, and if the permission test and data export recovery are successful, the selection review is complete.

Author's perspective: Supabase is recommended as the default for new web SaaS. This is because the relationship between customer, organization, and payment data increases over time, and SQL and standard Postgres are advantageous for analysis and transfer. On the other hand, if the team has field mobile apps with network interruptions, chat-centric products, or FCM/Crashlytics are important, Firebase reduces development costs even more. We do not recommend making a decision based solely on the free number on the price list.