Casting a board to a TV or monitor

Works on any board. The endless board (Supporter Upgrade) fills the whole screen, frame and all.

The short version: start casting first, then frame the board, then lock it. The lock keeps the same area of the board on every screen, fitted to that screen’s shape, so nobody has to pan or zoom.

Three ways to get the board on the big screen

Mirror your phone or tablet. Use your phone’s Screen Cast, Smart View or Screen Mirroring (AirPlay on an iPhone). It’s the quickest way, but the TV shows everything on your phone, menus included, so anything you open while editing appears on the TV too.
Cast a browser tab from a computer. In Chrome, open the board, then ⋮ menu → Cast… → Sources → Cast tab, and pick the TV. Only that tab goes to the TV.
Open the board on the TV or monitor itself (its own browser, or a computer plugged into it), and edit from your phone. The audience only ever sees the board, and your menus stay on your phone. The TV catches up with your changes by itself within about ten minutes, or at once if someone presses the refresh button in its zoom bar (the circling arrow).

Why the order matters

A phone that starts mirroring often changes its own screen shape to match the TV. A phone held sideways is usually wider than a TV, so when casting starts, the picture on the phone is cut down at the top and bottom (or the sides) to the TV’s shape. A board framed before that is framed for a shape that is about to go away. Start casting first and frame the board on the shape the TV will actually show.

You don’t have to get it perfect. The lock is an area of the board, not a zoom level, so any screen that opens the board, whatever its shape, shows that whole area as large as it fits. A screen of a different shape just shows a little more board around it.

Locking the view

Press the padlock in the zoom bar (or Lock the view for casting in the menu).
Read the steps and press I understand. They get out of the way, leaving a small Lock this view button at the bottom, so the whole board is in view while you frame it.
Start casting, if you haven’t already.
Go full screen if your browser’s bars are showing (the corners button in the zoom bar). Not every browser allows full screen, and the button only appears where it works; Safari on an iPhone doesn’t allow it. There, turn the phone sideways and scroll the bars away.
Pinch and drag until the screen shows what the TV should show.
Press Lock this view.

While it’s locked

Nobody can pan or zoom, on any screen that opens the board.
The controls fade away after a few seconds, so the TV shows only the board. Tap anywhere to bring them back.
You can still pin things up, and drag items around the board.
To change something without hunting for it on the screen, open the menu and choose Items on the board. Pick one and its settings open; the board stays where it is.
A screen showing the board checks for changes every ten minutes and catches up by itself, so edits from another phone or computer appear within about ten minutes. To show them sooner, tap the screen and press the refresh button (the circling arrow) in the zoom bar.
To move the view again, press Unlock in the zoom bar, or Unlock the view in the menu.

If something looks off

The TV cuts off the edges of the frame. Many TVs zoom in slightly (“overscan”). In the TV’s picture settings, set the picture size to Screen Fit, Just Scan, 1:1 or Full Pixel, whichever your TV calls it.
There is extra board around the framed area. That’s the screen being a different shape from the one you framed on. Unlock, frame again on the screen that matters, and lock.
The phone goes to sleep and the cast stops. Lengthen the phone’s screen timeout while casting, or keep it plugged in.