JSSpeccy 3
JSSpeccy 3 is a free ZX Spectrum emulator that runs in a web browser.
What JSSpeccy 3 is
JSSpeccy 3 is a free ZX Spectrum emulator that runs in a web browser. It emulates the Spectrum 48K, Spectrum 128K, and Pentagon, and handles both documented and undocumented Z80 instructions. Its display reproduces scanline and multicolour effects with cycle accuracy, and it supports AY and beeper audio. You can load SZX, Z80, and SNA snapshots, along with TZX and TAP tape images using traps; supported files can also be opened from ZIP archives. Display options include 100%, 200%, and 300% zoom, plus fullscreen. The emulator runs in a Web Worker, with its core compiled to WebAssembly from AssemblyScript. It can be embedded in a website, with settings for machine selection, zoom, auto-start, tape loading, and file controls. Loading files hosted on another domain requires that domain to provide CORS headers. JSSpeccy 3 is licensed under GPL version 3, and its maker describes it as a personal project without a commitment to technical support.
Good
- Emulates Spectrum 48K, 128K, and Pentagon machines
- Supports documented and undocumented Z80 instructions
- Loads snapshots, tape images, and ZIP files
- Offers AY and beeper audio
- Free and licensed under GPL version 3
Watch out
- Remote files require CORS headers
- Maker does not commit to technical support
Who it suits
It suits people who want to run ZX Spectrum software in a browser or embed an emulator on a website. Its supported machines and snapshot and tape formats are useful to users with compatible files.
Verdict
JSSpeccy 3 covers three Spectrum machine types, several snapshot and tape formats, and multiple display options in a browser-based emulator. Check remote-file requirements and the lack of a support commitment if those matter to your use.
The facts
Each one read from JSSpeccy 3's own pages, with the date it was checked.
What it does
- Audio
- It supports AY and beeper audio.checked 4 Oct 2026
- Configuration
- Embed options include machine selection, zoom, auto-start, tape auto-loading, file loading by URL, and disabling file-opening controls with sandbox mode.checked 4 Oct 2026
- Display
- It provides cycle-accurate scanline and multicolour effects, with 100%, 200%, 300% and fullscreen display modes.checked 4 Oct 2026
- Display accuracy
- It provides cycle-accurate emulation of scanline and multicolour effects.checked 4 Oct 2026
- Display modes
- It offers 100%, 200%, 300% and fullscreen display modes.checked 4 Oct 2026
- Embedding
- The project is designed to be embedded in websites using its JavaScript file and a page element for the emulator.checked 4 Oct 2026
- File formats
- It loads SZX, Z80 and SNA snapshots, plus TZX and TAP tape images using traps; supported files can also be loaded from ZIP archives.checked 4 Oct 2026
- Implementation
- The emulator runs in a Web Worker, with its core compiled to WebAssembly from AssemblyScript.checked 4 Oct 2026
- License
- JSSpeccy 3 is licensed under GPL version 3.checked 4 Oct 2026
- Notable limit
- Loading remote files by URL is subject to browser security restrictions; files hosted on another domain need to be served with CORS headers.checked 4 Oct 2026
- Processor emulation
- It handles documented and undocumented Z80 instructions.checked 4 Oct 2026
- Purpose
- JSSpeccy 3 is a ZX Spectrum emulator that runs in a browser.checked 4 Oct 2026
- Remote file loading
- Loading files from another domain requires that domain to serve CORS headers.checked 4 Oct 2026
- Support
- The maker describes it as a personal project and makes no commitment to provide technical support or assistance.checked 4 Oct 2026
- Supported files
- It loads SZX, Z80 and SNA snapshots, plus TZX and TAP tape images via traps, and can load these formats from ZIP files.checked 4 Oct 2026
Where it runs
- Emulated machines
- It emulates the Spectrum 48K, Spectrum 128K and Pentagon machines.checked 4 Oct 2026
- Supported machines
- It emulates the Spectrum 48K, Spectrum 128K and Pentagon machines.checked 4 Oct 2026
The company
- Maker
- The official site credits Matt Westcott as the maker.checked 4 Oct 2026
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