The interface

One screen does the work: a 3D view of your build plate, with panels around it. Nothing is hidden behind menus.

┌──────────────┬─────────────────────────────────────┬──────────────┐
│              │  tool cluster        Model | G-code │  viewport    │
│   Settings   │                                     │  cube        │
│    panel     │           3D build plate            │              │
│              │                                     │  G-code      │
│  Printer     │                                     │  inspector   │
│  Filament    │                                     │              │
│  Process     │  Objects                            │  ▸ Slice     │
└──────────────┴─────────────────────────────────────┴──────────────┘

That's the layout on a computer. A tablet gets the same one with the side panels folded down so the plate stays the biggest thing on screen — see On a tablet. A phone gets the same tools in a one-handed arrangement — see On a phone.

The 3D view

The bed, the print volume, and your models. Navigate it the way you'd expect:

• Drag to orbit, scroll to zoom, right-drag (or two fingers on a trackpad) to pan.
• Click a model to select it, Esc to deselect, Ctrl/⌘ + A to select all.
• Ctrl/⌘ or Shift + click adds to the selection. With a finger or a pen, press and hold a model and choose Add to selection, or use the Multi-select tool — see Working the plate with a finger or a pen.
• Right-click (or press and hold on a touch screen) a model for duplicate, drop to floor, centre and remove, without leaving the plate. On empty bed you get the plate-wide actions instead.
• The viewport cube top-right snaps the camera to a face, edge or corner. Click its centre to return home.
• Shift + Space switches between perspective and orthographic. Orthographic is the honest one when you're checking whether something is square.

On a trackpad or tablet, a two-finger swipe orbits by default. If you'd rather it panned, change it in Settings → Controls. Palm rejection is on by default for pen input.

On a touchscreen, two fingers pinch to zoom and slide to pan — both at once, as you'd expect. Twisting rotates the view, but only if you clearly mean it: once you've started pinching, the view won't tip just because your wrist turned. Rest your hand on the glass while drawing with a pencil and it's ignored.

The tool cluster

Floating under the model, this is where you manipulate what's on the plate.

Tool	Key	What it does
Select & move	M	Drag handles to move; also plain selection
Rotate	R	Spin around an axis
Scale	S	Resize, uniformly or per axis
Pull to floor	F	Click a face; that face becomes the bottom
Paint support	B	Brush support enforcers and blockers onto a model
Place objects	A	Auto-arrange everything on the bed
Multi-select		Touch and pen only — each tap adds or removes
Add a model		Same as dropping a file in
Gravity	G	Objects drop to the floor after every move
Model / preview	P	Switch between the model and the sliced G-code

Picking a tool opens a small card with numeric fields — exact position, rotation in degrees, size in millimetres or percent. Type a number if dragging isn't precise enough. The card docks down the left edge of the plate, not under the toolbar: your models sit in the middle of the view, and a card there covers the very thing the tool is for — painting a model you can't see is no use.

One tool at a time, one card at a time. Picking a tool puts the last one's card away, and the card names the tool you are holding.

You can stay on the keyboard. Tab from the plate jumps straight into the open card — onto the X field, the brush mode, or the Place button, whichever the tool calls for — and Esc hands you back to the plate. Multi-select is the exception: it changes what the next tap does rather than replacing the tool, so it sits apart from the others and stays on across them. Esc drops the placing tool back to select-and-move.

The plate-editing tools disappear in G-code preview. There's nothing to edit there, and a change you can't see happen is worse than no change.

The settings panel (left)

The panel floats over the left edge of the plate. The pin on its edge keeps it open — the plate's contents move over to make room — or hides it. Hidden, a slim bar marks the plate's left edge: rest the pointer anywhere along that edge and the panel opens, then move away and it closes. Click or tap the bar to keep it open until you click elsewhere.

Three rows at the top name what the plate is made of — printer, filament and process. Click a row to show its settings below; the ⋯ beside it swaps the profile or opens it for editing.

While the plate uses one of the generic starter printers, a note under those rows says so and links to Add your printer — its bed size and start G-code are a guess until you do. It goes away as soon as a printer of your own is picked.

Changed a setting and want to keep it? The save button in the top row writes the changes you tick back into their profiles.

Ctrl/⌘ + F jumps to the search box. Type "infill", "seam", "brim" and the groups filter down. This is usually faster than remembering which tab something lives in.

Full tour: Print settings.

The objects panel (bottom left)

Every model on the plate, with its triangle count and size. Select from here when the 3D view gets crowded.

Watch for the warning badges: outside the build area, and overlaps another object. Both are warnings, not blocks — you can still slice, but you probably shouldn't.

Each row also has Duplicate and Remove. Remove asks once ("Click again to remove") before it does anything, and Undo brings a removed model back. Copies of the same model are numbered — benchy.stl (1), benchy.stl (2) — so each row names one object. Add models under the list puts more files on the plate, alongside what is already there.

On a touch screen the panel starts folded to a chip with the object count, because it sits on top of the plate it describes and a finger can't hover it out of the way. Tap the chip to unfold it; it stays however you leave it. A warning triangle appears on the folded chip if something can't print where it sits.

The slice button (bottom right)

Press Slice (or ⌘/Ctrl + Enter). While it runs the button reads Cancel and stops the slice. Afterwards the result button — Download, Upload or Print — becomes the main button and Re-Slice steps back beside it. Change something and it turns around again: Re-Slice turns amber, and the result button disappears until you re-slice, so a stale file can't be saved or sent.

Below it, a status line: Ready to slice → Slicing… → Sliced · N layers · 4.9s, or a red failure with the reason. The time in that line is how long slicing took.

On the right of the same line sits the filament the print uses — 13 g, plus the cost when the filament profile has a price per kg — and the estimated print time, ~1h 12m. It is worked out from your process settings — the speeds and accelerations the G-code actually asks for. It is not worked out from your printer's limits, because the slicer does not have them: a machine that cannot reach a commanded speed simply takes longer than the figure says. Treat it as a good guide to whether a plate is a coffee or an afternoon, not as a countdown.

It doesn't always wait for you. See Re-slicing on its own.

Once it succeeds, the result button lets you Download, Just upload, or Upload & print. It remembers which you used last. Upload & print always asks before it starts the printer.

Re-slicing on its own

Some plates come back in a second; some take a minute. Waiting for the button every time is tedious on the first kind and unavoidable on the second, so the slicer decides from how long that plate's last slice actually took. Each plate is judged on its own, so a heavy one can sit quiet while a light one keeps up.

Once you've sliced once, a flash button appears next to the Model | G-code switch. Click it to step through three settings:

Setting	What happens
Automatic	Re-slices by itself while slices stay quick; waits when they don't
Always	Re-slices after every change, however long it takes
Off	Nothing happens until you press Slice

The icon says which: a bolt with an A for Automatic, a plain bolt for Always, a struck-through bolt for Off. It's lit whenever changes are re-slicing themselves, and its tooltip says what it decided and what this plate's last slice cost — so a plate that has gone quiet tells you why.

The timing is remembered for as long as the app is open and no longer. After a reload the first slice is yours to press, which is what re-establishes it.

An automatic re-slice waits about a second after you stop, so dragging a model across the bed or typing a temperature is one slice, not one per frame. While one is queued the status line reads re-slicing shortly — press Re-Slice if you'd rather not wait.

The default is Automatic, and you can change it for good in Settings → General → Slicing.

Whether the view follows the slice

A finished slice normally switches the 3D view to the G-code preview. That's what you want when you pressed Slice and were waiting for it — and not what you want in the middle of arranging a plate, because the plate-editing tools are hidden in preview, so the next drag lands on a view that can't show it.

Settings → General → Slicing → Show the preview after slicing decides:

Setting	What happens
Automatic	Follows a slice you pressed; leaves an automatic re-slice alone
Always	Every finished slice switches to preview
Never	The view never changes on its own — use the switch or P

It never switches away from the preview, so if you're already inspecting a slice you stay there whatever re-sliced it.

The G-code inspector (right, after slicing)

Appears when you switch to G-code with the Model | G-code switch at the top right. Choosing G-code before there is a slice starts one. Colour the toolpaths by role, speed, temperature and more; hide path types you don't care about; scrub through layers and through individual moves. See Reading the preview.

Tap its G-code header to fold it away when the legend is in front of what you're trying to see — the layer counter stays, the Slice button stays put, and the slicer remembers what you chose.

Notifications

Anything about the plate — a model being added, a job going to a printer, a change someone else made — appears as a pill at the top of the scene, just under the view toolbar. A longer job fills its pill as it runs and finishes in the same one, so you never have to look somewhere else for the result. Most fade after a few seconds; hovering one holds it while you read.

Messages about the app itself, like a new version waiting to be loaded, dock at the bottom of the window instead — the top of the screen on a phone, where the sheet isn't.

Everything else says its piece where it happened: a preset that would not import says so in the picker, and a slice reports its result — including why it failed — on the Slice button's own status line.

Moving between Home, Slice and Settings

When you first open the app it shows the Cold Crabby logo with a progress bar beneath it. The logo appears immediately as a soft, low-detail version and sharpens a moment later once the full artwork has downloaded. The bar follows the real download, so it tells you how much is genuinely left.

The rail on the left switches between the three areas. The app loads each one the first time you open it, so on a slow connection the first visit can take a moment.

When it does, you'll see it: a thin amber line runs along the top of the work area, and the rail item you're heading to shows a spinner. Nothing appears for a switch that's already instant — which is most of them, because the app quietly fetches the other areas in the background once it's finished starting up.

If the app was updated while your tab stayed open, a part it hasn't loaded yet may have already been replaced on the server. Rather than failing silently, it offers you a Reload banner. Take it — a reloaded tab is a consistent one.

Workplate tabs

The title bar keeps a tab for every workplate you have open, the way a browser keeps a tab per page. Uploading a model, opening a recent project, or following a link into a workplate all open a tab; clicking one switches to that workplate.

• Rename a tab by double-clicking it, or right-clicking and choosing Rename. Spaces are fine, and the box grows as you type. The box opens with the current name selected, so you can type straight over it; Enter saves, Esc cancels, and clearing it puts the automatic name back. The same name is used for the downloaded G-code file.
• Move between tabs from the keyboard with ← and → once a tab has focus — Home and End jump to the ends, Enter switches, F2 renames.
• Start a new workplate with the + at the end of the strip. It takes you Home, where you can open a model, drop one in, or pick up a recent project — the workplate you were on keeps its tab and is exactly where you left it.
• Close a tab with its ×, or by middle-clicking it. Right-click a tab for Close Other Tabs, Close Tabs to the Right and Close All Tabs. Closing the workplate you're looking at switches you to the next tab over, or Home if it was the last one open. Closing a tab only removes it from the strip — the workplate itself isn't deleted, and you can always get back to it from Home → Recent projects.
• Find an open workplate with the ⌄ beside the +, ⌘/Ctrl + Shift + A, or Search Open Workplates in a tab's right-click menu. It lists every open workplate; type to narrow it down, use ↑ and ↓ to pick one, and Enter to switch to it. It appears once you have more than one tab.
• More tabs than fit shrink to share the bar, then scroll: use the mouse wheel over them, and the workplate you're on always scrolls back into view.

Switching tabs reloads that workplate: its models, where you put them, the profiles it was set up with and the settings you changed on it. That takes a moment for a large workplate, and the viewport says so while it happens.

Undo

Ctrl/⌘ + Z undoes, Ctrl/⌘ + Y (or ⌘ + Shift + Z) redoes. This covers what you do to the plate — moving, rotating, scaling, adding, deleting, arranging. Delete or Backspace removes the selected models, and undo brings them back. While you're typing in a settings field or a name box the shortcut belongs to that field, so it undoes your typing rather than the plate.

On a touch device without a keyboard, undo and redo buttons appear in the 3D view toolbar so you can step through history without a shortcut. They show up automatically on touch tablets and phones; force them on or off any device in Settings → Controls.

Settings and profile edits are not undoable. They're saved deliberately, and changing a value back is the undo.

Making it yours

Settings is split in two down its sidebar. App is how this app behaves on this device — General, Appearance, 3D View and Controls. Library is what you slice with — your printers, filaments, processes and labels, each with a count, and the three that slice name the one that is the default. The box at the top searches all of it: a preference, one of your profiles by name, or any printer, filament or process setting, and picking a result takes you to it.

Every preference is one line of what it does; the ⓘ beside its name opens the longer explanation in place, which works on a tablet where a tooltip would not.

Settings → Appearance has light / dark / system, and an accent colour: the default molten amber, five other presets, or — on macOS and Windows — whatever your system accent is set to.

Settings → 3D View has the graphics knobs, grouped by what they are about: how models look, the camera's field of view, what the view costs (anti-aliasing, render resolution, preview detail) and the thumbnail. Turn the performance ones down on a weak GPU, up on a good one.

Settings → General holds Re-slice after a change, the app-wide setting behind the flash button — the same three choices, with a line telling you what your last slice took and what Automatic is doing about it.

Two of them are about the thumbnail embedded in sliced G-code, which is shot in the 3D view rather than by the slicer. The screenshot animation is the flash and the little preview card that flies off to the top after each capture — turn it off if you'd rather the shot were taken quietly; it is still taken. Thumbnail look decides whether the model is rendered plainly or with this view's own shading, gloss and contact shadow. What goes in the picture — its angle, background and colour — is a print setting, under Process → Thumbnail.

On a tablet

An iPad has the screen for the full layout but not the mouse, so two things change: everything is bigger, and nothing that floats over the plate stays open on its own.

• Panels start folded. The G-code inspector and the objects list each show just a header — G-code · 42 / 180, Objects 2. Tap a header to open it, tap again to fold. Your choice sticks from then on.
• Print settings are a drawer, behind the slim bar on the plate's left edge. Tap it to open, tap outside to close — and that tap still lands where you aimed it, so selecting a model or spinning the camera closes the drawer in the same move. The plate stays visible beside the drawer rather than being dimmed out.
• Panels use the room they have. Unfolded, the G-code inspector shows its whole legend and both sliders without scrolling.
• Everything is finger-sized. Buttons, dropdowns, the layer slider and the legend chips grow for a fingertip, and stay that size when you pick up an Apple Pencil, so switching between pen and finger never shifts the layout.

Split View and Slide Over shrink the window, and the layout follows: below about 1024 points wide you get the folded arrangement on any device, including a narrow window on a desktop.

Working the plate with a finger or a pen

• Tap a model to select it. Tapping is judged generously: a fingertip is a wide, soft target that never lands and lifts on the same pixel, so a tap still counts as a tap even when it slides a little. Tap empty bed to deselect.
• Press and hold a model for the same menu a right-click gives: duplicate, drop to floor, centre, remove — acting on the whole selection if you have one. Hold on empty bed for select all, clear, place objects and reset view.
• Build a selection from the same menu. Hold a model outside the selection and choose Add to selection; hold one inside it for Remove from selection; hold a lone selected model for Select more. Adding keeps the selection you had rather than replacing it.
• Multi-select, in the tool cluster, is the stand-in for holding ⌘/Ctrl. While it's on, each tap adds an object to the selection or takes it back out; turn it off to go back to one-at-a-time. Adding from the menu turns it on for you. It appears once there are at least two objects to choose between, on a touch screen or while a pen is in use.
• Drag a selected model to slide it across the bed. Select it first, then drag: one deliberate tap means nothing gets shoved out of place by a stray swipe. Dragging anywhere else still orbits the camera, and the move handles are drawn larger so a fingertip can pick one axis rather than all three.
• Palm rejection is on by default. While a pen is in use, the hand resting on the glass is ignored, so the view doesn't lurch mid-stroke. Turn it off in Settings → Controls if you never use a stylus.
• The sidebar's edge resizes at the same width as on a desktop. It's a thin line on purpose: a fat invisible grab zone hanging over the plate turned taps near the panel into accidental resizes, and resizing is a slow, deliberate drag you were never going to start by mistake.

Two fingers pinch to zoom, drag to pan and twist to roll, anywhere on the plate.

On a phone

The same app, rearranged for one hand. There is no separate mobile version and nothing to install — open the slicer's address in your phone's browser.

┌─────────────────────────────┐
│ 🦀  My plate              ● │  ← title bar
├─────────────────────────────┤
│        [ tools ]            │
│                             │
│                             │
│         3D plate            │
│                             │
│                  Objects 2  │
│  ┌───────────────────────┐  │
│  │ model.stl     ▸ Slice │  │  ← slice sheet
│  └───────────────────────┘  │
├─────────────────────────────┤
│  Home      Slice    Settings│  ← tab bar
└─────────────────────────────┘

• Navigation moves to the bottom, where your thumb already is.
• Slice lives in a sheet across the bottom of the plate, with the file name and the download / send buttons beside it. After slicing, the G-code inspector opens inside that sheet and scrolls — Slice stays put.
• Print settings are a drawer. Tap the slim bar on the left edge. Tap anywhere outside to close — the tap reaches the plate as well, so it doubles as your next gesture.
• The objects list is folded to a chip showing how many models are on the plate. Tap it to open the list; a warning triangle appears on the chip if something can't print where it sits, so a folded list never hides a problem.

Two things are left out rather than squeezed in: the viewport cube (drag it with what?) and the projection toggle. Reset-view — the house icon — still frames the plate in one tap, and both come back the moment you open the slicer on something wider. Everything that actually gets a model sliced is there.

Turned sideways, the chrome shrinks to give the plate the height back: the tab bar drops its labels and the panels get shorter.