FTA Studio vs Isograph FaultTree+
Isograph's FaultTree+ has been the de-facto desktop tool for fault tree analysis for over 25 years. FTA Studio is a browser-based alternative — IEC 61025-compliant, free for the Community edition, $99/seat for Enterprise. Here's an honest, side-by-side comparison so you can pick the right tool for your project.
At a glance
| FTA Studio | Isograph FaultTree+ | |
|---|---|---|
| Deployment | Browser-based, no install | Windows desktop install |
| Pricing entry point | $0 (Community, no expiry) | Quote-based, ~£3,000+ /seat (perpetual) |
| Free trial | Community is free forever | Time-limited eval |
| OS support | Any OS with a modern browser | Windows only |
| IEC 61025 symbols | ✓ | ✓ |
| MOCUS minimal cut sets | ✓ | ✓ (also BDD) |
| Importance measures | ✓ (Birnbaum, FV, RAW, RRW) | ✓ |
| Monte Carlo | ✓ (Enterprise) | ✓ |
| FMEA | ✓ (Enterprise) | Separate Isograph product (FMECA+) |
| Event Tree Analysis | ✓ (Enterprise) | Separate product (EventTree+) |
| Common-cause failure | ✓ (Beta, MGL) | ✓ |
| Approval workflow / audit trail | ✓ (Enterprise) | ~ via separate Isograph product |
| Data privacy | Browser-only; nothing leaves device | Local install; nothing leaves device |
| Tree size limit | Practical: thousands of nodes | Tens of thousands of nodes |
| Industry templates | 8 included free (auto, aero, rail, medical, etc.) | Sample library |
| IEC JSON interchange | ✓ native | Proprietary .ftt + XML export |
| Vendor | FTA Studio (independent) | Isograph Ltd (UK, est. 1986) |
The honest differences
When to pick FTA Studio
- You want to start in 10 seconds. No install, no licence dance, no IT ticket. Open a browser, go to the URL, build a tree.
- You need cross-platform. Mac, Linux, Chromebook, Windows — anything with a browser works identically.
- Budget is tight. Community is free forever — full IEC 61025, MOCUS, importance measures, every export format, multi-page diagrams. No trial expiry, no node limit.
- You're a small team or contractor. Per-seat pricing at $99/year is roughly an order of magnitude lower than legacy desktop tools.
- Your data must stay local. Community is 100% in-browser — nothing phones home. Compatible with ITAR / CUI-controlled work where SaaS is forbidden.
- You want to share work via URL. Templates open with one click; trees export to JSON anyone can re-open without paying for a viewer.
When to pick Isograph FaultTree+
- You're modelling extremely large trees. Tens of thousands of nodes with deep CCF — FaultTree+ has had 25 years to optimise BDD-based engines for this.
- You need BDD as well as MOCUS. Both algorithms have edge cases where one wins; FaultTree+ ships both.
- You're already in the Isograph suite. Round-tripping with Reliability Workbench, FMECA+, EventTree+, AvSim and HAZOP+ saves migration cost if you've already paid.
- Your customer mandates Isograph. Some defence and aerospace primes name FaultTree+ specifically in their bid criteria.
- You need 24×7 vendor support with named contacts. Isograph's enterprise contracts include named technical support; FTA Studio is currently email-only.
Pricing — the real number
Isograph doesn't publish list pricing. From customer-shared quotes, FaultTree+ typically runs £2,500–£3,500 per seat (perpetual licence) plus annual maintenance at ~20% of list. A 5-seat team is therefore £12k–17k upfront plus £2.5k/year ongoing.
FTA Studio Community is free forever. Enterprise is $99/seat/year — a 5-seat team is $495/year, no upfront. That's two orders of magnitude lower TCO over five years.
The pricing gap reflects what each tool is built for: FaultTree+ is an established commercial product with named-account sales and 24×7 support; FTA Studio is a lean, modern alternative for teams that want IEC 61025-compliant analysis without the procurement overhead.
Standards coverage
Both tools cover the IEC 61025:2006 symbol set and computational primitives. Both are used in ISO 26262, ARP 4761, EN 50126, MIL-STD-882 and IEC 61511 contexts. Compliance of your analysis is your responsibility either way — the tool gives you the vocabulary; the safety case is yours to make.
FTA Studio's standards reference pages map every clause of IEC 61025 to a concrete feature. Browse the worked industry templates to see how each standard's deliverable is structured.
Pricing and feature details for Isograph FaultTree+ are based on public information and customer-shared quotes as of April 2026. We're not affiliated with Isograph; their product is a strong, well-maintained commercial tool. If you spot something out of date, email support@ftastudio.app and we'll correct it.