z390
z390: A free, open-source choice for running and developing mainframe assembler and COBOL programs. Ranked #35 of 37 in Emulator Software by our editors (5.8/10); pricing: Free plan; best for mainframe assembler and COBOL execution.
At a glance
- Editor score5.8 / 10
- PricingFree plan
- Best forMainframe assembler and COBOL execution
- Free planYes
- Paid fromFree
- Supported targetsIBM System/360 subset, System/370, System/390, and z/Architecture instruction sets through z17
- Facts checked21 Sep 2026
Where it wins
- Supports IBM System/360 through z/Architecture instruction sets through z17
- Includes assembler, linker, emulator runtime, and COBOL execution
- Runs on Windows, macOS, and Unix-like systems with GUI and scripts
Where it doesn't
- Its focus is narrower than general-purpose emulator software
- COBOL and assembler workflows center on IBM mainframe environments
- Documentation does not describe network-condition simulation or state snapshots
Our verdict on z390
z390 is a Java-based, open-source toolkit for developing, testing, and running IBM mainframe assembler and COBOL programs on personal computers. It is aimed at mainframe programming education and application development when direct access to a mainframe is not available. The toolkit supports IBM System/360 subset, System/370, System/390, and z/Architecture instruction sets through z17, with Windows, macOS, and Unix-like host support.
Its strongest feature is the breadth of the mainframe development workflow in one package. z390 includes an IBM HLASM-compatible macro assembler, a linker for relocatable object files and load modules, an emulator runtime, and COBOL program execution. It also covers QSAM and VSAM-compatible file processing, TN3270-compatible data streams, and CICS-compatible transaction processing. Interactive execution tracing and test mode add debugging support, while TCP/IP client and server socket services extend the environment beyond local program execution.
The project also offers practical automation options through command-line scripts alongside a graphical interface. That combination suits learners, developers, and teams working with assembler or COBOL code across multiple desktop operating systems. z390 is free and open source, making it a strong fit when the priority is accessible IBM mainframe emulation and development. Its narrower focus makes it less suitable for buyers seeking a broad emulator platform or documented tools for simulating network conditions and capturing emulator state snapshots.
Your product? Our editors can test z390 in depth and publish a review, labelled as paid · from $149/mo →
z390 pricing
z390 fact sheet
| Free plan | Yes |
|---|---|
| Paid from | Free |
| Supported targets | IBM System/360 subset, System/370, System/390, and z/Architecture instruction sets through z17 |
| Host operating systems | Windows, macOS, and Unix-like systems |
| Hardware acceleration | Not verified |
| Snapshots and restore | Not verified |
| Debugging tools | Yes |
| Network simulation | Not verified |
| Automation access | Yes |
| Deployment | Desktop |
| Platforms | Windows, macOS, Linux |
| Support | Community, Docs |
| Built for | Solo, Small business, Mid-market (editorial estimate) |
| Pricing | Free plan |
| Website | z390development.github.io |
| Facts checked | 21 Sep 2026 |
Alternatives to z390
- QEMUA broad, free emulator for complete machines, operating systems, and CPU architectures.9.4
- Wind River SimicsA deep simulation environment for teams validating complex systems before hardware is available.9.2
- Android EmulatorA free, broad Android testing environment with strong device and automation coverage.9.1
Used z390? Be the first to review it
The editor score above is our own research. What this page doesn't have yet is a reader's view — what you used z390 for, what worked and what didn't. No stars are seeded and no review is paid for; an editor reads every one before it appears.
Write a reviewTwo minutes · verified accounts only · read by an editor before it appears
Featured on iTechGuides
z390 is listed in our Emulator Software directory. Add the badge to your site — it links back to this page.
<a href="https://www.itechguides.com/products/z390/"><img src="https://www.itechguides.com/best/badge/z390.svg" alt="Featured on iTechGuides" width="230" height="46"></a>
Reviewed by iTechGuides Editors · Editorial team · Updated Oct 2026
Advertiser disclosure: iTechGuides is reader-supported. Vendors can pay for top positions in our rankings and for a place on other products' pages, and we may earn a commission when you click some links. Bought places stand at the number bought; this page and our disclosure say so. Paying vendors may get a fuller, more detailed review from our editors, and that review can change their score. How we rank.
Last updated · How we research and update