Download

Get the ISO 8583 simulator

No installer, no service, no administrator rights. Unzip the archive and run the binary — the app creates its own database on first launch.

Recommended build

FlexSim for Windows

61.7 MB · ZIP archive · 64-bit · Windows 10 or later

Download

Version 1.0.4 · Not your platform? Every build is listed below.

All builds

Five targets, same application

Each archive is self-contained: the runtime is inside the binary, so there is nothing else to install.

Windows · x64 FlexSim-1.0.4-win-x64.zip · 61.7 MB Download macOS · Apple silicon FlexSim-1.0.4-osx-arm64.tar.gz · 58.9 MB Download macOS · Intel FlexSim-1.0.4-osx-x64.tar.gz · 62.0 MB Download Linux · x64 FlexSim-1.0.4-linux-x64.tar.gz · 59.4 MB Download Linux · ARM64 FlexSim-1.0.4-linux-arm64.tar.gz · 56.3 MB Download

All five builds are current. Every archive is published from the same source revision, so a suite exported on one platform imports on any of the others without conversion.

Release notes

What changed, and when

Every numbered release, newest first. Only the current one is on the download host — upgrading is a folder swap, and your profiles, cards, keys and suites stay where they are.

  1. 1.0.4 Current
    • Card values recalculate as you type
    • Track 2 follows the card unless you type it yourself
    • Import a captured message into a response
    • A warning before saving a field with nothing in it
    • Bug fixes
  2. 1.0.3
    • Reversals copy subfields from the request
    • Import a captured message into a reversal
    • A filter box on the specification editor
    • All four specification profiles ship again
    • Bug fixes
  3. 1.0.2
    • Fixed the tooltips that slowed the app down and swallowed clicks
    • Bug fixes
  4. 1.0.1
    • Packaging fixes
  5. 1.0.0
    • First numbered release
    • Specification fixes now reach installs that already exist

Setup

Installing takes three steps

The details differ slightly per platform, mostly because of how each one treats a program it has not seen before.

Windows

Unzip and run

  1. Unzip FlexSim-1.0.4-win-x64.zip anywhere you have write access.
  2. Run FlexSim.exe. Keep Assets\simulator.db beside it.
  3. SmartScreen may warn on first launch — choose More info, then Run anyway.
macOS

Expand and clear quarantine

  1. Expand the archive: tar -xzf FlexSim-1.0.4-osx-arm64.tar.gz
  2. Move FlexSim.app to Applications.
  3. The build is unsigned, so the first launch needs right-click → Open, or xattr -dr com.apple.quarantine FlexSim.app.
Linux

Extract and launch

  1. Extract: tar -xzf FlexSim-1.0.4-linux-x64.tar.gz
  2. Run ./FlexSim from the extracted folder.
  3. The executable bit is already set in the archive. If you repackaged it as a zip, run chmod +x FlexSim first.

The macOS build is not a single file. Its bundler leaves the Skia, HarfBuzz and Avalonia native libraries outside the binary, so they ship inside the app bundle beside it. Keep the bundle intact. Windows and Linux really are the executable plus Assets/simulator.db.

Before you start

What FlexSim needs

Very little. The .NET runtime is compiled into the binary, so there is no framework to install and no version to match.

  • Windows 10 or later, macOS 12 or later, or a glibc 2.23 Linux
  • About 200 MB of disk once extracted
  • No administrator rights, no registry entries, no background service
  • Outbound TCP to whatever host you are testing, and a listening port for acquirer mode
First launch
// the app seeds its own database
Database: %LOCALAPPDATA%\FlexSim\simulator.db
Specs: 4 profiles loaded
Ready — 2.8 s to first window
Your data never touches the folder you unzipped into, so replacing the build with a newer one leaves everything intact.
Coming from FluxPay

Your data comes with you

FlexSim was previously called FluxPay. On its first run it looks for the old user data folder and copies the database, the write-ahead log and your log files across to the new one — so your profiles, cards, keys and suites are simply there.

  • It copies rather than moves, so the old folder stays as a fallback
  • It runs only when the new folder does not yet exist
  • Delete the old folder yourself once you are happy
Upgrading

Replace the folder

Close FlexSim, delete the extracted folder and unzip the new one. Your profiles, cards, keys and suites live in the user data folder and are picked up automatically. Copy that one file to move everything to another machine.

Removing

Delete two things

Delete the extracted folder, and delete the FlexSim folder under your user data directory if you also want the database and logs gone. Nothing else was written anywhere on the machine.

New to FlexSim?

The feature reference walks through both roles, spec profiles, message composition and card data — in the order the app puts them in front of you.

Read the feature reference Back to the overview

Use FlexSim only against systems you are authorised to test