Abacus

The self-hosted personal finance movement has a mobile gap problem. Abacus is the serious attempt to close it.

TL;DR

• What it is: A free, open-source (GPL-3.0) iOS and Android mobile client for Firefly III — the self-hosted personal finance manager. Abacus is not a standalone app; it requires a running Firefly III instance [README][App Store].
• Who it’s for: People already running or considering Firefly III who need mobile access to their transactions, budgets, and net worth without logging into a browser [README].
• Cost savings: YNAB costs $109/year. Monarch Money costs $99/year. Copilot costs $79/year. Abacus + Firefly III self-hosted on a $6 VPS costs roughly $72/year total — for the entire backend, not just the app [App Store].
• Key strength: Zero external data transmission. Tokens live in iOS Keychain or Android Keystore. No analytics, no Sentry, no Crashlytics — your financial data stays inside your own infrastructure [README].
• Key weakness: Incomplete feature coverage compared to the Firefly III web interface, and at least one reviewer noted compatibility issues with Firefly III 6.4.0 where categories and charts stopped working correctly [App Store].

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What is Abacus

Abacus is a mobile app built by Victor Balssa that lets you interact with a self-hosted Firefly III instance from your phone. Firefly III is the actual personal finance engine — the thing that stores your accounts, transactions, budgets, categories, and net worth data on a server you control. Abacus is the client that lets you reach it without opening a browser.

The distinction matters because it shapes what you’re actually evaluating. You’re not choosing between Abacus and YNAB directly — you’re choosing between the Firefly III ecosystem (self-hosted server + Abacus mobile app + web interface) and a fully managed SaaS finance app. Abacus is one layer of that stack, and whether it’s good depends heavily on how well it surfaces the most frequently used Firefly III features in a native mobile interface.

The project is built on Expo SDK (React Native), uses OAuth2 for authentication, and stores access tokens in platform-native secure storage — iOS Keychain on Apple devices, Android Keystore on Android. The GitHub repository sits at 806 stars, which is modest but appropriate for a specialized companion app targeting a niche self-hosted tool. The App Store listing shows 43 ratings averaging 4.9/5, which is a small but consistently positive signal [App Store][README].

No external API calls means exactly what it says: Abacus communicates only with your Firefly III instance and nothing else. If you’ve spent any time thinking about where your transaction data goes when you use Mint or Plaid-connected apps, this is the architecture you actually want [README].

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Why people choose it

The App Store reviews tell a consistent story across three years of the app’s existence, which is itself meaningful — most self-hosted companion apps either get abandoned or accumulate increasingly angry reviews as compatibility falls behind.

One reviewer in mid-2024 put it plainly: “This app is great. It doesn’t do everything, but it has the most essential elements I want on mobile, including biometric lock. It’s very stable and looks clean. It is built for mobile rather than based on the Firefly III web client, which I appreciate a lot.” [App Store] That last sentence is the important part. Abacus is a purpose-built mobile interface, not a responsive wrapper around the web app. That choice makes the daily transaction-entry and balance-checking experience feel native rather than awkward.

An earlier reviewer put it more tersely: “Simple, clean, and easy to use. Huge kudos to the dev for making such a quality app for such an underappreciated project like Firefly III.” [App Store]

The “underappreciated project” framing captures something real. Firefly III has existed since 2013 and has a dedicated user base, but the self-hosted personal finance space has never had the same developer attention as self-hosted infrastructure tools. Abacus filling the mobile gap for free — with no ads, no subscription, no tracking — is a meaningful contribution to a community that tends to move at its own pace.

The biometric lock feature mentioned by reviewers is a practical detail that matters for a finance app. Requiring a fingerprint or Face ID to open the app is table stakes for something you’d carry around with your bank balances visible [App Store].

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Features

Based on the README feature table and App Store description:

Authentication and security:

• OAuth2 authentication against your Firefly III instance [README]
• Tokens stored in iOS Keychain / Android Keystore — not in app storage [README]
• No external API calls of any kind — no analytics, no crash reporting [README]
• Biometric lock (Touch ID / Face ID / Android biometric) [App Store reviews]

Financial views:

• Net worth display with multi-currency support [README][App Store]
• Asset accounts history chart [README]
• Balance overview [README]
• Earned (income tracking) [README]
• Time range selector for filtering views [README]

Transactions:

• Create new transactions [README]
• List transactions [README]
• Account filtering and date-based filtering [changelog]
• Deep-link support to specific transaction dates [changelog]

Budget and planning:

• Budgets view [README]
• Categories view [README]
• Piggy bank tracking [README]
• Bills display on home screen (added in v0.15.0) [changelog]

Internationalization:

• Translations available including Italian, Russian, Ukrainian [changelog]
• Community-contributed translations [README]

What’s notably absent compared to the web interface:

• Full reporting and charting capabilities
• Rule management (auto-categorization rules)
• Recurring transaction setup
• Account reconciliation
• Data import/export
• Full bill management beyond display

The app is genuinely mobile-first for daily use cases — entering a transaction after a purchase, checking your remaining budget for the week, reviewing net worth — but it doesn’t attempt to replicate everything the web interface can do [App Store reviews][README].

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Pricing: SaaS vs self-hosted math

Abacus itself: Free. GPL-3.0 licensed, available on the App Store and Google Play at no cost. The developer accepts GitHub Sponsors [README].

The full stack cost is really about Firefly III hosting:

• Firefly III on a $6 Hetzner VPS: ~$72/year
• Firefly III on a shared VPS you’re already running for other self-hosted tools: effectively $0 marginal cost
• Abacus mobile app: $0

Comparison against managed personal finance SaaS:

• YNAB: $109/year (or $14.99/month)
• Monarch Money: $99/year
• Copilot: $79/year (iOS only)
• Mint: discontinued in early 2024, forcing millions of users to find alternatives
• Quicken Simplifi: $47.99/year

For a household that was paying YNAB pricing, switching to Firefly III + Abacus saves roughly $100/year after VPS costs. That math is straightforward. The harder question is whether the feature set difference is acceptable, and that depends entirely on how much you were actually using the reporting and automation features of whatever SaaS you’re leaving.

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Deployment reality check

Abacus itself has no deployment step — you install it from the App Store or Google Play like any other app. The deployment work is in Firefly III.

What you need:

• A running Firefly III instance reachable over HTTPS — either on your home network or a VPS with a domain and TLS certificate [App Store][README]
• The Firefly III OAuth2 client credentials configured (the app walks you through this)
• Your Firefly III URL, which needs to be accessible from your phone (not just on your local LAN unless you’re using a VPN)

What can go sideways:

• If Firefly III is only on your home LAN, you’ll need a VPN (WireGuard, Tailscale) to reach it from your phone when you’re out. This is a real friction point for non-technical users.
• One App Store reviewer in September 2025 flagged that with Firefly III 6.4.0, categories weren’t appearing and charts weren’t rendering correctly: “I’m currently using Firefly-III 6.4.0 and have noticed some compatibility issues. For example, when I switch to the ‘Categories’ tab, my created categories don’t appear, and the charts don’t work properly.” [App Store] This is the classic self-hosted compatibility lag — the app needs to track API changes in Firefly III across major versions.
• HTTP (non-HTTPS) requests are supported via a setting added in v0.14.0 for LAN-only setups [changelog], but running without TLS on a public-facing instance is a bad idea for a finance app.
• Initial OAuth2 setup can be confusing for non-technical users. The README links to a dedicated authentication help doc, which suggests it generates enough support questions to warrant documentation [README].

Realistic setup time:

• If you already have Firefly III running with HTTPS: 10 minutes.
• If you’re starting from scratch: budget 2–4 hours for the VPS, domain, reverse proxy, and Firefly III installation before you even open the app.

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Pros and cons

Pros

• Zero cost. Free to download, GPL-3.0 source, no subscription, no in-app purchases [README][App Store].
• Genuine privacy. No external API calls, no analytics, no crash reporting. Tokens in platform-secure storage. Your financial data touches only your server and your phone [README].
• Purpose-built for mobile. Not a web view wrapper. The interface is designed around the use cases you actually do on a phone: enter a transaction, check a balance, look at net worth [App Store reviews].
• Active maintenance. Version history shows consistent releases through 2025 with genuine feature additions (Ukrainian translations, switching between asset/all accounts in history charts, date deep-linking) and real bug fixes, not just version bumps [changelog].
• Biometric lock. Standard expectation for a finance app, and it’s there [App Store reviews].
• Multi-currency net worth. Useful if you hold accounts in multiple currencies, which Firefly III handles well [README].
• Cross-platform. iOS (iPhone + iPad) and Android (phone + tablet) [README].

Cons

• Requires Firefly III. This is not a standalone app. If you don’t have Firefly III running, Abacus is useless. The app is a complement to an existing self-hosted stack, not an entry point to one [README][App Store].
• Incomplete feature coverage. The web interface does significantly more — rule management, full reporting, data import, reconciliation. Mobile is useful for day-to-day operations, not for setup or analysis [App Store reviews].
• Compatibility lag risk. The September 2025 review flagged broken categories and charts with Firefly III 6.4.0 [App Store]. One developer maintaining a mobile app against a frequently-updated backend is a known risk for self-hosted companion projects.
• Small community. 806 GitHub stars is small. If the developer loses interest, the app could fall behind Firefly III API changes and stop working. GPL-3.0 means someone could fork and continue it, but that’s not guaranteed.
• No web fallback. If you need to do something the mobile app doesn’t support (create a rule, reconcile an account, run a report), you’re back to the browser. For a phone-native experience, this means context-switching.
• Remote access setup friction. Getting the app to work away from home requires either a public-facing Firefly III instance (security considerations) or a VPN — neither of which is trivial for non-technical users.

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Who should use this / who shouldn’t

Use Abacus if:

• You’re already running Firefly III and want a clean mobile interface for daily transaction entry and balance checking.
• You’re evaluating Firefly III as a YNAB/Mint replacement and mobile access is a requirement — Abacus answers whether that requirement can be met.
• Privacy is a genuine concern. You want your financial data to stay on hardware you control, with no intermediary services seeing your transaction history.
• Your use case is primarily “enter transactions and check balances” on mobile — not analysis, not import, not rule-building.

Don’t use Abacus if:

• You don’t have Firefly III running. The app has no standalone value.
• You need mobile access to the full Firefly III feature set. The app covers the common daily operations but not the full surface area.
• You’re a non-technical founder with no experience running self-hosted software and no one to help. The VPS + reverse proxy + OAuth setup is a real barrier.
• You need guaranteed long-term support. Single-maintainer GPL apps can go quiet. If you’re betting your financial tracking on this stack, have a contingency.

Stay on YNAB/Monarch if:

• You’re happy with the pricing and don’t have privacy concerns about your transaction data going through third-party servers.
• You rely on automatic bank import via Plaid or similar. Firefly III supports import but it requires more setup and doesn’t have the seamless bank sync that YNAB offers.
• You want professional-grade customer support. A solo open-source developer with a GitHub Sponsors link is not a support team.

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Alternatives worth considering

The relevant comparison set depends on whether you want self-hosted or managed:

If you want self-hosted:

• Firefly III — the backend that Abacus is built for. Has its own web interface; Abacus is additive, not required.
• Actual Budget — newer self-hosted personal finance tool with a more modern UI and better mobile story (though still maturing). Growing quickly.
• Budgetz — lighter weight self-hosted option with a simpler feature set.

If you want managed SaaS:

• YNAB — the gold standard for budget methodology, $109/year, Plaid bank sync, solid mobile apps.
• Monarch Money — YNAB competitor with better net worth tracking and investment views, $99/year.
• Copilot — iOS-only, excellent design, $79/year.

For the target audience — founders who are specifically trying to escape SaaS billing and want privacy — the relevant shortlist is Firefly III + Abacus versus Actual Budget. Actual Budget has received more developer attention in the last two years and may have better mobile support; Firefly III is more mature and battle-tested.

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Bottom line

Abacus does exactly one thing: it gives you a clean, private mobile interface for your Firefly III instance. It does that thing well — consistent reviews over three years say the app is stable, the UI is clean, and the core operations (enter transactions, check balance, view net worth) work. The trade-offs are equally clear: you need Firefly III already running, feature coverage is partial compared to the web interface, and compatibility with newer Firefly III versions isn’t guaranteed to stay current given single-maintainer dynamics.

If you’re building the self-hosted personal finance stack as an alternative to $100+/year subscription apps and mobile access is a requirement, Abacus is the most credible option for Firefly III and it costs nothing. If you’re starting from scratch and choosing a stack, weigh Actual Budget alongside Firefly III before committing — the mobile story may be more complete.

If the VPS + Firefly III setup is the blocker, that’s the kind of one-time infrastructure deployment that upready.dev handles for clients — you pay once, you own it, and the recurring SaaS bill disappears.

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Sources

1. App Store — Abacus for Firefly III (43 ratings, 4.9/5). Victor Balssa. https://apps.apple.com/us/app/abacus-for-firefly-iii/id1627093491

2. GitHub — victorbalssa/abacus (README, feature table, changelog, 806 stars, GPL-3.0). https://github.com/victorbalssa/abacus