17The big idea
Here's what makes Slate, Slate. Open the player and your board redraws itself — every stroke in the order you made it, as if you were writing it live. It plays in beats, the natural steps of your explanation, and you're in full control of the tempo.
Find itThe Export / Share button → Launch player.
Use itPress play and watch it redraw. Step through beats, give each one a caption, change the speed, or scrub the timeline to land anywhere.
Just one part of itA whole board is not always what you want to show at once. Tools → Region lets you drag a rectangle around one worked example, one column of a table, one step of a proof — and replay only the marks inside it, in the order you drew them, while the rest of the board stays exactly as it is. A region follows the beats, exactly as the player does, so a detached diagram replays in its own order rather than the order its parts happen to sit in — a flowchart draws a box, then the arrow leaving it, then the next box, inside a region just as it does in a full replay. Arming it puts the Select pointer in your hand so the first drag makes a rectangle rather than a mark, and hands your tool back when you leave. Pull a corner to resize the rectangle or drag its middle to slide it; a mark counts as inside if any part of it is, and it always plays whole rather than cut off at the edge. Play, Pause and Stop do what they say; space is play/pause and Esc leaves. Nothing about it changes the board — when it finishes, or the moment you stop, every mark is back where it was, and the file is not touched. Clearing the board takes the region with it.
Speed, and darkening the restSpeed is a slider from 0.25× — a crawl, for a class copying it down — to 8× for a quick recap, and it can be moved while the replay runs. Darken the rest of the board holds everything outside the rectangle back behind a veil while it plays, so thirty pairs of eyes land on the one thing being built; its own slider sets how dark, from a light shade to nearly black. The veil covers the board only, never the surround, and the region itself stays at full brightness.
During a showIt is on the show bar too, beside the spotlight — so “let me show you how this one was built” needs no leaving the lesson. Everything works the same; only saving is left out, because a file is a board-mode job.
Four ways, one at a timeA region is used one way at a time, and the card shows only that way’s controls. ▶ Play replays the marks inside the rectangle. ☼ Cover blurs it so you can rub it clear by hand. ⊞ Split makes equal parts shown one at a time. ✂ Cut lets you draw cuts of any shape and number the parts. Choosing one clears what the last one left — so a Split never lands on top of freehand cuts, and a region you keep comes back as the one thing you made rather than all four mixed together. Switch freely: the rectangle stays where it is.
Cover it, then show itDrag a region round the work, then press ☼ Cover. What is behind it goes blurred — the class can see something is coming without being able to read it — and the region’s outline stays visible so you know where it is. Now rub over the cover with your finger, the pencil or the mouse and that part comes clear, sharply, and stays clear. Nothing is cropped, split or copied: it is the same work underneath the whole time. Show all takes the cover off.
Cutting it into partsFor a worked solution or a list, Split into 2, 3 or 4 equal parts — one tap, no dragging — and ↔ switches between splitting across and splitting down. For parts that are not equal, press ✂ Cut: the region is covered so you can see the whole area, a guide line follows your pointer, and each tap lays a cut where that line is. The pieces between the cuts are the parts, so they can never overlap, never fall outside the region, and always cover the whole of it. Drag a cut to move it, tap one to take it away, and Undo takes back the last cut — while you are cutting it leaves the board alone. The parts are numbered on the board in the order they will show; Next shows the next one, Prev puts the last one back, and every part you have shown stays showing. Cutting across and down at the same time gives you a grid, shown row by row. You can still rub the cover by hand at any point, so a planned sequence and a free reveal are the same thing.
Cuts of any shape, and your own numbersA grid is the wrong shape for most of what gets taught — a diagram, a map, a worked example with a picture in the corner. So a cut can be a line you draw, and a part is whatever your lines enclose. ╱ Straight drags a straight cut, and you only need to drag across the middle: both ends reach the edge on their own. ✎ Freehand draws a cut any shape at all — round one lung, one country, one corner of the working — and finishing near where you started cuts out an island in the middle. While you draw, the end of the line is marked: green means it will join up and close a part, orange means it stops in mid‑air and will not. Ends near an edge or another cut snap onto them, and an end left just short is extended to reach. Tap a cut to take it away, and the presets above still work — a hand‑drawn cut across a Split 3 simply makes six parts.
You give the parts their numbersSlate does not decide the order — it cannot know whether the heart comes before the lungs. Press # Number and tap the parts in the order you want them — one tap gives a part its number, no keyboard needed. Tap a numbered part again to take its number off. When the order is not simply “next”, a long press (or a right-click) opens a box to type a number, and typing one already in use swaps the two parts. Play, Next and Prev then walk the parts in your order, not in reading order. Tap a numbered part to take its number off; a part with no number simply is not in the lesson yet, and the parts still waiting are the ones with no number on them. The card tells you how many parts there are, how many are numbered, and whether any cut has a loose end. Nothing is painted over your work while you cut — each part is simply outlined, so a photograph or a diagram stays exactly as it is. And the moment you start showing the lesson — Play, Next, a full-screen show, or a live class watching — every cut line and number disappears: they are your working-out, not part of the lesson, so the class sees only the picture coming out from under the cover. A part shows as its own shape when the cover lifts — a crescent reveals as a crescent, not as the rectangle around it. Clear numbers keeps the cuts; Clear cuts starts again; and Undo takes back your last number, then your last cut, before it ever touches the board. Keep saves the way you were using the region along with its cuts and numbers, so recalling gives back exactly what you made and nothing else, and everything reaches a live class as you do it.
Keep a region for next time★ Keep saves the whole region — its area, every step inside it, and the speed and darkening — under a name you give it, like “Worked solution” or “Question reveal”. Kept regions are listed in the card: tap a name to play it, ↺ to bring it back as the region you are working on, ✎ to rename and × to remove. What is kept is the area, never a copy of the work, so a kept region always plays whatever is on that part of the board now — correct the working and the same reveal shows the corrected version. They are saved in the Slate file, so they are there when you open it again tomorrow and can be played as often as you like. A board has no kept regions until you make one, and a file from before this existed simply has none.
Lesson recapAt the end of a lesson, play back what you taught. Tools → Lesson recap (or 🎓 Lesson recap… in the Region card) lists every region you kept, on every board — untick one to leave it out, and ↑ ↓ to change the order; both are saved with the lesson, so next time’s “last time we…” is the same list. Choose Show me or Test yourself, a replay speed (1×, 2× or 4×), and whether to darken the rest of the board. Start recap opens a card listing what you covered; then each step goes to its board, outlines the region with its name at the top (“2 of 6 · Quadratic formula”) and shows it the way it was kept: a Play region replays its working, a Cover region is covered to rub clear (or Show it all), and Split and Cut regions show their parts one at a time. The big button always says what it will do next — Next part, Show it all, Skip to end, Next — and ◀ goes back. Keys: Space or → moves on, ← goes back, Esc ends. Test yourself covers each one first and asks “What do you remember about this?” with a 5, 10 or 20-second countdown (or until you press Reveal), then shows it — recalling before seeing is what makes a recap stick. In a live session everyone follows on their own screen, and 🎲 Who explains? (or Pick a student to explain each one) names a student for the step on screen, never the same one twice; that student is told You — explain this one!. At the end, 🖨️ Recap sheet (PDF) prints every step as a picture with its name and the date, two to a page — students in the session get their own Save my recap sheet, made from their own screen as the recap went by. Nothing on the board changes, and you finish on the board you started on.
Diagnostics, when something goes wrongTools → Diagnostics (students: Help → Diagnostics) records a short trace to send to whoever is fixing Slate. Turn it On just before the problem, do what goes wrong, then open the small diag chip at the bottom left and press Save trace (a file you can attach) or Copy report. Each time it is turned on it starts a fresh log, so the trace holds only that stretch. It records errors and warnings, which buttons and menu items were pressed and which keys (never what is typed into a box), the messages sent and received in a live session, where the pointer went, and a snapshot of the boards, the session and every activity. Turn off (in the chip, or the same menu item) stops it. A trace can include students’ names, so send it to the person fixing Slate rather than posting it.
First time, names and shortcutsThe first time Slate opens it offers four ways in — Start drawing, Host a class, Join a class or Take the tour; it does not ask again. On a tablet or phone, press and hold any button to see its name. With a keyboard, press ? for every shortcut, and Tab reaches the board in a couple of presses (closed menus are skipped). Several messages at once now queue rather than overwrite each other; tap a message to clear it.
Save just that regionIn board mode the panel also offers PNG, APNG and WebP under Save. These give you the region on its own, rendered as a small slate — the board’s own surface and frame behind it, trimmed to the rectangle — so it drops into a worksheet looking like Slate rather than like a ragged screenshot. PNG is the still. APNG and WebP are animations of the region drawing itself, in the same order the region replays in, and they follow the speed slider above them — a slow one for a class copying it down, a fast one for a recap. Handy for a revision sheet, a slide, or sending one worked example to a student who missed it.
Part of the Slate guide — or read the whole guide on one page.