zbCAD Documentation

zbCAD is a 2D drafting tool modeled on the drawing conventions common to desktop CAD software: a typed command line that accepts abbreviations, keyboard shortcuts, and coordinate expressions like @3,2 or @5<45; object snap to precisely pick existing geometry; layers; and associative dimensions that stay attached to the geometry they measure. If you've used a traditional desktop CAD package before, most of this will already feel familiar.

Everything lives in your browser tab. Drawings are saved to a local .zbCAD.json file you download and re-open yourself, and an autosave copy is kept in the browser's local storage so an accidental tab close doesn't lose your work.

zbCAD is built for a mouse and keyboard on a wide display; it has no touch input handling or small-viewport layout. A narrow window or a touch device shows a dismissible warning to that effect rather than silently breaking — Continue anyway skips it for anyone who wants to try regardless.

The window is divided into a few fixed regions:

• Toolbar (top) — grouped buttons for File, Edit, Draw, Modify, Annotate, Inquiry, and View. Buttons that start a command show its keyboard alias in parentheses, e.g. Line (L). The Auto-hide button next to the zbCAD logo collapses it down to that slim brand bar, freeing up canvas height; mouse over the bar (or Tab into it) to bring the toolbar back as an overlay without resizing the canvas underneath it. This preference is remembered per browser.
• Canvas (center) — the drawing area. Left-click to pick points or select objects, scroll to zoom, middle-drag to pan, right-click or Enter to accept the current command's default action.
• Layers panel (right) — lists every layer with its visibility, lock, and color controls; collapsible via the ▸ / ◂ toggle at its top.
• Command line & status bar (bottom) — the text input where you type commands, coordinates, and keywords, plus toggle buttons for SNAP, ORTHO, POLAR, the active object-snap set, the drawing units, the current file name, and the live cursor coordinates.
• Inquiry panel — a small overlay that appears with the result of DIST, AREA, ID, or LIST; close it with the × button or Esc.

The command line

Click a toolbar button, or click the command-line input and type a command name (or its alias, e.g. L for LINE) and press Enter or Space. You don't need to click into the input first — typing any single character while the canvas has focus jumps into the command line automatically.

While a command is running, the same input accepts, in order of precedence:

1. A keyword the active command is listening for (its prompt tells you which letters are live, e.g. C to close a polyline, U to undo the last point).
2. A point, typed as x,y, @x,y (relative to the last point), or @distance<angle (polar, relative).
3. A command-specific value (an angle for ROTATE, a scale factor for SCALE, etc.).
4. A bare distance, applied along the direction from the last point toward the current cursor position — type a number right after picking a start point and dragging toward a direction to draw an exact length without doing the trigonometry yourself.

An unrecognized string that matches none of the above is looked up as a new command name.

Entering points & distances

A leading - negates a distance; a leading + is accepted and ignored.

Object snap

With SNAP on (the default), moving the cursor near existing geometry pulls the pick point onto a precise feature of it — essential for drawing connected geometry instead of eyeballing it. Click the snap-type readout in the status bar (next to the SNAP toggle) to choose which snap types are active:

When several snap points coincide on screen, the one listed first above wins, rather than whichever happens to be a pixel closer.

Ortho & polar tracking

ORTHO (F8) constrains the next point to be exactly horizontal or vertical from the current base point. POLAR (F10) instead locks onto the nearest multiple of a chosen angle increment (45° by default — change it via the polar readout in the status bar) whenever the cursor comes close to that alignment ray; move further off the ray and the lock releases. The two are mutually exclusive — ORTHO is really polar tracking at a fixed 90° increment, so turning one on turns the other off. Both only apply to commands that opt into tracked point entry (drawing and most modify commands); commands that ask you to pick a location rather than a measured point (e.g. which side of a line to keep when trimming) ignore both.

Selection & grips

With no command running, click an object to select it, or drag a box: dragging left-to-right selects only objects fully enclosed by the box, dragging right-to-left selects anything the box touches. Hold Shift to add to the current selection instead of replacing it. Delete erases the current selection. Commands that operate on a selection (MOVE, COPY, ERASE, ...) use the same picking and box-selection behavior at their "select objects" prompt.

Selected objects show small square grips at their defining points (endpoints, center, etc.). Click and drag a grip to reshape or reposition that point directly, without starting a command; click a grip without dragging to leave the edit live and then type or pick a destination point.

Layers

Every object lives on exactly one layer. The layers panel lists each with a radio-style "make current" marker, an editable name, a color swatch, a visibility toggle, a lock toggle, and a delete button. New objects are drawn onto the current layer, chosen from the dropdown above the panel or by clicking a layer's marker. Locked layers can't be edited; hidden layers don't render and aren't picked by selection or snap.

Assign selection to current moves the selected objects onto whichever layer is current. Layer 0 can't be renamed or deleted, and the current layer can't be deleted while it's current.

Units & dimension style

Open Units (UN) to set the drawing's physical unit (inches, feet, millimeters, centimeters, meters) and how lengths are displayed:

The units dialog offers to rescale existing geometry when you change the drawing unit, so switching from inches to millimeters mid-drawing doesn't silently change what your geometry means.

Dim Style (DST) controls how dimension objects are drawn: arrowhead style (tick or arrow), overall scale, text height, arrow size, and text precision (or "follow the document" to always match the current unit precision). New drawings default to arrows in metric units and ticks otherwise, matching common drafting convention.

Files & autosave

Save downloads the current drawing as a <name>.zbCAD.json file through the browser's normal download mechanism. Open loads a .zbCAD.json file back in. New clears the canvas (with a confirmation if it isn't already empty).

Every change is also autosaved to the browser's local storage after a short delay, and the previous autosave is kept as a backup slot. If a drawing is still open in browser storage when you return — a crash, an accidental tab close, forgetting to Save — zbCAD offers to recover it. Recover Backup in the toolbar explicitly restores the older, previously-autosaved slot (rather than the most recent one) if you need to step back one version, and replaces the current drawing when used, so Save first if you want to keep a copy of what's currently open.

Autosave and manual Save are a convenience, not a substitute for keeping your own backups — both live only in this browser's storage or wherever you chose to save the downloaded file.

Plotting to PDF

Plot (PLT) writes the drawing to a PDF as real vector geometry — not a screenshot of the canvas. Lines stay lines, so the sheet can be measured, marked up, and printed at any resolution. Ctrl/Cmd+P opens the same dialog.

The dialog previews the sheet live as sheet size, area and scale are chosen, drawn from the same plot plan the PDF is serialised from, so there is nothing between choosing options and seeing what lands on paper. Anything that falls outside the printable border is shown in amber rather than left off the preview, since a line half on the sheet and half clipped is exactly the mistake this is meant to catch before the file is written. Text too small to read at preview scale is greeked into a bar instead of vanishing — annotation that is really on the sheet shouldn't look absent in the picture of it. The dialog widens to two columns to fit the preview, collapsing back to one on a narrow window.

Sheet size offers the ANSI, ARCH and ISO sizes, in either orientation, with a half-inch margin the plot is fitted inside and clipped to. Plot area is the drawing extents, the current view, or a rectangle you pick on the drawing with Pick window (the dialog steps aside for the two corners and comes back with the window filled in).

Scale is the part that has to be exact. Fit to the sheet works out whatever scale makes the plot area fill the page; Exact scale takes a drawing scale — 1/4" = 1'-0", 1" = 20', 1:100 — and plots at precisely that, so a hundred-foot wall at 1" = 20' measures five inches on the sheet. If an exact scale is too large for the sheet the plot still runs, clipped at the margin, and says so before you commit to it.

Color plots monochrome by default: layer colors are chosen to read on the dark drawing area and several of them are nearly invisible on white paper. Plot layer lineweights uses each layer's millimetre lineweight; turned off, everything plots thin. Objects on hidden layers and on layers marked non-printable are left off the sheet entirely — that is what the layer panel's printable toggle is for.

Draw

Modify

Transform

Annotate

Inquiry

Inquiry commands are read-only: they never modify the drawing or create an undo entry.

Other commands