JNEXT

Overview

JNEXT is free software under GPLv3, created by Jorge Gonzalez (ZXjogv). It emulates Spectrum 48K, 128K, +2A/+3, and ZX Spectrum Next Issue 2 machines. Its combination of emulation, debugging, and CI-oriented automation makes it more compelling for development than for users seeking only a simple player.

The maker directs questions and bug reports to the GitHub issue tracker. The project says it has no ads or products for sale, and no trackers beyond a self-hosted page counter.

Key features

Emulation and peripherals

JNEXT models ULA and Timex video modes, Layer 2, 128 hardware sprites, tilemap, and Copper, alongside three AY-3-8910 chips, a DAC, and a beeper. Support for DivMMC and SD card, Multiface, DMA, UART, CTC, SPI/I²C, a real-time clock, USB gamepads, and Kempston mouse gives developers a broad set of machine components to work with.

It emulates the ESP-01 WiFi module so Next software can reach the real network, though networking is off by default. Next boots NextZXOS from an SD-card image; JNEXT can fetch the official distribution on first run when none is configured. The original and working images together use about 2 GB of disk space, a meaningful cost for a setup that relies on the default images.

Development, testing, and files

The debugger provides hardware views, registers, breakpoints, and backward execution. That is a substantial advantage for diagnosing software behavior compared with an emulator focused only on running programs. Headless operation and deterministic screenshots support CI testing without a graphical session.

JNEXT handles NEX, SNA, SZX, and Z80 snapshots, plus TAP, TZX, WAV, and RZX tape or session formats. RZX captures input alongside a machine snapshot and can be replayed in an emulator modeling the machine the same way. It can record video with audio to MP4 when ffmpeg is installed, and record audio to WAV without ffmpeg or a sound card.

Pricing

Free software — 0.00 USD per free. The plan is GPLv3, with no ads and nothing for sale. There is no paid tier or trial to weigh against the free option. That makes it a straightforward choice for developers who want open-source tooling without a purchase; the trade-off is that questions and bug reports go through the GitHub issue tracker.

Platforms

Packages are offered for Linux, Windows, and macOS; Linux packages include deb, rpm, and Flatpak. Windows users should expect a SmartScreen warning because the executable is not code-signed. On macOS, the app is ad-hoc signed but not notarized, so Gatekeeper blocks its first launch. These launch restrictions add friction before use, particularly for users who expect a conventional signed application.

Who it's for

JNEXT is best for developers working on ZX Spectrum Next programs who need inspectable machine state, reversible execution, and repeatable CI checks. Its broad peripheral and file-format support also suits people moving programs and recordings among Spectrum setups. It is a weaker fit when extreme cycle-exactness is essential, or when a project still under development and platform security prompts are unacceptable.

Pros and cons

• Pros: Built-in hardware views, registers, breakpoints, and backward execution make it useful for debugging rather than emulation alone.
• Pros: Headless mode and deterministic screenshots give CI workflows a direct way to exercise and capture programs.
• Pros: Support for Next hardware, peripherals, and common snapshot, tape, and session formats covers varied development workflows.
• Cons: Extreme cycle-exactness is not a project goal, ruling it out for work that depends on that level of timing fidelity.
• Cons: Windows SmartScreen warnings and macOS Gatekeeper's first-launch block make initial setup less seamless.
• Cons: The NextZXOS images take about 2 GB together, and the project remains under development.

Alternatives

For other ZX Spectrum emulators, browse ZX Spectrum Emulators. Unreal Speccy Portable is another free, open-source choice, with Android support in addition to Linux, macOS, and Windows. Klive IDE is a free, open-source option for Linux, macOS, and Windows, described as a not-for-profit passion project.

zx_go is a free, open-source emulator for Linux, macOS, and Windows; its licensed Spectrum Next ROMs are not bundled. CSpect is another free option, with no support or warranty and no guaranteed updates. GZX is free software for Linux and Windows, with ZX Spectrum ROM files excepted from its MIT-style license.

ZEsarUX is free software for Linux, macOS, Windows, and self-hosted use, with optional donations. Spectral is a free, open-source experimental emulator whose code is prone to change. RustZX is an open-source option for Linux and Windows.

Verdict

Choose JNEXT if you are developing ZX Spectrum Next software and want debugging and CI automation in a free, GPLv3 emulator. Look elsewhere if exact cycle timing is central to your work, or if you need a project beyond development status with uncomplicated first launch on Windows or macOS.