About FIXSIM Browser-Based FIX Protocol Testing Since 2012

How FIXSIM Started

FIXSIM was built by Gregg Drumma, founder of Gamma Three Trading, LLC, based in Boston, Massachusetts. While building an Order Management System, we needed a reliable way to test FIX protocol workflows without relying on live counterparties or expensive on-premise software.

We chose to build our own solution. Once internal teams saw its value for development, QA, and support workflows, we launched FIXSIM as a cloud-hosted platform in 2012. The response was immediate — financial firms across the globe needed exactly what we had built: on-demand FIX protocol testing accessible entirely through a browser, with no software to install.

More than 13 years later, FIXSIM processes over 2 million FIX messages daily and is trusted by broker-dealers, buy-side firms, OMS/EMS vendors, exchanges, and fintech teams worldwide.

Our Philosophy

Accessibility

FIXSIM is entirely browser-based — no downloads, no VPN, no infrastructure setup required. Connect from anywhere using TLS-encrypted sessions. FIXSIM can act as a FIX initiator, acceptor, or both simultaneously, giving teams the flexibility to simulate any counterparty configuration.

Flexible Pricing

Whether you are an independent software contractor or a large global fintech vendor, FIXSIM offers plans to fit your needs. Month-to-month subscriptions with no annual contracts. We serve software vendors, investment managers, broker-dealers, and individual developers.

Manual and Automated Workflows

Log into the FIXSIM portal to view real-time FIX message flows, inspect orders and executions in the trade blotter, and manually trigger order actions. For teams that need repeatable, automated testing, the Rule Builder creates deterministic test scenarios that run without manual intervention.

For full CI/CD integration, the FIXSIM REST API gives your application direct programmatic control over sessions, message injection, and scenario execution — enabling zero-touch regression testing in automated pipelines.

FIX Trading Community Member

Gamma Three Trading is a member of the FIX Trading Community, the non-profit standards body responsible for the FIX protocol specification. Membership ensures FIXSIM stays current with evolving FIX standards across all supported versions: FIX 4.0 through FIX 5.0SP2.