The player

zxplay.org is a ZX Spectrum player built for phones as much as for desktops: the screen and an on-screen Spectrum keyboard lay themselves out to fit whatever viewport you open it in, stacked in portrait and side by side in landscape. Turn the keyboard off and the screen takes its room.

It runs the same emulation core as everything else in this project, compiled to WebAssembly — 48K, 128K and a Spectrum Next that cold-boots real NextZXOS.

Loading something

Open a file from the menu, or link straight to one with the u query parameter. The engine sniffs the file rather than trusting its name, and loads snapshots (.sna, .z80, .szx), tapes (.tap, .tzx), .nex files, and zip archives containing any of those.

https://zxplay.org/?u=https://example.org/games/mygame.tap

u may be repeated to open several files in sequence.

The program's own needs generally pick the machine: opening a .nex moves the emulator to the Next, a .tap on a Next moves it back to the 128K. The menu's checkmark follows those switches rather than going stale.

URL parameters

Older links using m=5 (Pentagon) still work — the value maps to the 128K, the closest supported machine, rather than failing.

The keyboard matches the machine

The on-screen keyboard is the one the selected machine actually has:

The two 58-key layouts add the keys the 48K makes you type as combinations — EDIT, DELETE, GRAPH, EXTEND MODE, CAPS LOCK, TRUE and INV VIDEO, BREAK, the cursor keys and ; " , . — which is what makes the 128K menus, the NextZXOS Browser and the BASIC editors usable without a physical keyboard. They press the same keys underneath as a real machine does: EDIT holds CAPS SHIFT and 1. The on-screen keys show what the machine sees, so a key you press lights up, and so does one the running program is holding down.

All three are drawn rather than pictured — every key rectangle, every legend, the shape of each moulding and the colours transcribed from a reference, the 128K and Next from photographs of the real machines and the 48K from the key art it replaces. So what you press is what the hardware looks like, down to the keyword printed on each key, but crisp at any size and nothing to download. All three draw into the same box, so switching machine moves nothing on the page.

Pressing an on-screen key also hands your real keyboard to the emulator, just as clicking the screen does, so the two can be used together: press EDIT on screen and carry on typing.

Switching machines switches the keyboard; nothing to set. When that is not what you want, the Keyboard menu names all three outright and the choice sticks until you change it — useful when a machine is running something its own keyboard does not suit, such as a Next in 48K mode, or a 48K program you would rather drive with the Spectrum+'s dedicated EDIT and cursor keys. The keys are matrix positions, so any keyboard drives any machine: BREAK on the Next's keyboard is CAPS SHIFT and SPACE, which is BREAK on a 48K too. Your choice is remembered, along with the machine and the joystick.

No keyboard, and a bigger screen

The same menu offers No Keyboard, for playing with a real keyboard in front of you. The screen then takes the room the keyboard had rather than leaving it blank: it is no longer held to twice the Spectrum's own size, and grows until it meets the window. On a 1920x1080 desktop that is a screen about 1250 pixels wide instead of 640. In landscape, where the screen already uses the full height, the keyboard simply goes: the screen has no use for the width it frees, so the column shrinks to the menu button that shares it and the two are centred together rather than left at opposite edges. Only View > Keyboard Side has nothing left to say, so it steps out of the menu.

Nothing else changes: clicking the screen still hands it your keyboard, and your choice is remembered like the rest. A game that names its own keys with the k parameter (below) still draws them — those are its controls, and on a phone they may be the only ones — so the choice comes back with the next game.

Pixel perfect

Filling the window means the screen is usually not a whole multiple of the Spectrum's own size, and the pixels are drawn hard-edged rather than smoothed. At 1250 pixels wide, for instance, each Spectrum pixel wants to be 3.9 across, so some are drawn 4 and some 3 — a faint unevenness across the picture, most visible on dithered artwork and single-pixel detail.

View > Pixel Perfect rounds the screen down to a whole multiple instead — 1x, 2x, 3x and so on — so every pixel is exactly the same size. It is off by default, because it costs whatever is left over: that 1250-pixel screen becomes 960, and on a phone in landscape it can be the difference between 488 and 320. The window decides which is the better trade, so it is a switch rather than a rule, and it is remembered like the rest.

Two cases where it does nothing. A screen already on a whole multiple — a desktop showing the usual 2x — does not move. And where not even 1x would fit, on a very narrow window, the screen keeps filling the space: there is no whole step left to drop to, and a screen shrunk below the Spectrum's own resolution would be a worse answer than uneven pixels.

Tailoring the keyboard to a game

Most games use four or five keys. Showing a full keyboard on a phone makes all of them small. The k parameter replaces the on-screen keyboard with just the keys your game uses, and the layout resizes to match — fewer keys means bigger keys. Keys you name this way are the 48K's rubber keys, and they are kept on every machine, so a game's play surface does not change size when the machine does.

The value is comma-separated rows of key characters. Letters and digits are themselves; four characters are special:

A row is capped at 10 keys. The full default keyboard is:

1234567890,QWERTYUIOP,ASDFGHJKLe,cZXCVBNMs_

So a Manic Miner link needs only:

https://zxplay.org/?u=...&k=OPeZ

and a game using QAOP plus space becomes k=-Q-,OP-_,--A or whatever arrangement suits the thumbs.

Whatever you show, the on-screen keys stay in sync with the machine's actual keyboard matrix — if the running program holds a key down, the on-screen key lights up.

Joysticks

A connected gamepad drives one of the classic interfaces: Kempston (the default, and the most common), Sinclair 1 or 2, or Cursor/Protek. A game reads exactly one and there is no way to detect which, so the choice is yours, and it is remembered.

On the Spectrum Next there is nothing to choose — the machine has a built-in Kempston joystick, so a gamepad works out of the box.

Spectrum Next games

The Next boots genuine NextZXOS, which means Next software loads the way it does on real hardware, with the consequences that implies for how a game must be packaged.

A bare .nex file is imported to the card as /zx.nex and launched through NextZXOS's own .nexload. That fixed short name sidesteps a real constraint: the SD card is FAT, long names get ~1-style aliases, and the command-line macro that types the load command cannot produce a ~.

A .zip containing exactly one .nex is treated as a game folder, and this is the form to distribute anything non-trivial in. Every file in the zip is staged onto a fresh card under the game's own folder, and the .nex is launched by driving the NextZXOS Browser to it — under its own name, in its own directory, from the launcher a player would really use.

That last part is not ceremony. Games that stream their own data reopen themselves by filename at runtime, and at least one known title exits to the menu if launched any other way. Preserving folder, filename and launch context is what makes it work. Every load starts from a pristine card, so a game cannot be affected by whatever ran before it.

A zip with no .nex in it keeps the classic behaviour: it should contain exactly one loadable file, and that is what opens.

What is actually running

The engine cold-boots the Next through the authentic FPGA chain rather than restoring a captured state, and every machine and video mode composites into a fixed 640×512 display, so the page layout never jumps when a program changes mode.

Next compatibility is the newest part of the project: some titles play, several render with bugs, and many are unverified. Game compatibility lists what has been tested.