You can bring in a puzzle from a newspaper, a web page, a photo, or another copy of Sudoku X4. The Import puzzle button (a clipboard with an arrow) opens the Import Puzzle screen. It is in the title bar of the album's front page, of each difficulty's page of games, and of the game screen.
Paste from clipboard pastes a puzzle you copied. If the clipboard holds a picture instead, such as a screenshot of a grid, it goes to the framing screen, just like a photo.
Scan QR reads a Sudoku X4 or sudoku.coach QR code with the camera, on a device or in a browser that can scan one.
Take photo (in the app on a phone or tablet) and From image read a picture of a puzzle; see Photos, below.
Enter manually opens the puzzle editor on an empty grid. Once the screen has read a puzzle, the same button says Fix in editor and opens the editor on what was read.
You can also type or paste into the text box. It takes an 81-character string, a sudoku.coach link, a .sdk or .ss grid, comma-separated values, a sudokux4.com or sudokux4:// link, or a Sudoku X4 game file (.sx4json). A game file comes in just as it was saved, progress and all, at its own difficulty; if digits or pencil marks have already been entered in it, winning it gets the ta-da.
As soon as the screen recognizes a puzzle, it shows the grid and what it found: the format, the variant, the difficulty (with the hardest technique needed), the number of clues, whether there is a unique solution, and whether the puzzle is solvable without guessing.
A puzzle with no solution, or with more than one, cannot be imported, and the screen says which.
You do not pick the difficulty. The app solves the puzzle and files it under the level its hardest step needs (see Difficulties). A puzzle that can only be solved by guessing is filed under Beyond Hell, and the preview says Solvable without guessing: no.
A plain grid cannot say whether it is an X puzzle. If yours has the two diagonals, tap Try as X-Sudoku; Not an X — undo takes that back.
Open Puzzle puts the puzzle in the album and opens it to play. Add to Album puts it in the album and shows it there.
A link sent with Where I am brings the sender's digits and pencil marks too. The preview says so, under In progress, and the game opens where they left it. Winning it gets the ta-da, not the applause, because part of the work was theirs.
A link from Share Puzzle opens the Import screen with the puzzle already entered: in Sudoku X4 itself on an iPhone, iPad or Android device that has the app, and in the web version anywhere else. A sudokux4:// link does the same in the installed app on an iPhone, iPad, Mac or Android device.
After Take photo or From image comes Frame the Grid. Drag the box over just the puzzle grid, and drag the gold handle at its corner to resize it; tighter is better. If the picture is sideways, turn it upright with the rotate buttons. Then tap Scan the grid.
The app reads the digits, and tries to read the regions of an irregular puzzle and the diagonals of an X. The result opens as Check the Grid: the editor, with the picture beside the grid, so you can fix anything it misread.
Tap a cell, then a digit; Erase clears it. With a mouse, a keypad appears beside the pointer, a right-click erases a cell, and dragging with the right button across several cells offers to erase them all.
The Irregular and X switches in the title bar set the variant. With Irregular on, the editor has three modes:
Digits enters the clues.
Regions draws the map. Pick a region by its number below the grid, then tap or drag across cells to paint them; the last button there erases. Under Symmetry, choose None, Rotate 180°, Mirror ⇆, or Mirror ⇅: with a symmetry chosen, each cell you paint also paints its counterpart under that symmetry, in the region paired with yours. Boxes starts over from the ordinary 3×3 boxes, and Clear empties the map. Each region must be 9 connected cells.
Colors sets the shading: tap a region, then a color. Regions that touch must differ.
Undo and Redo are in the title bar. So is Show the original image, which puts a picture beside the grid to check against: the one on the clipboard, or one you choose. Tap the picture to see it full size and zoom in.
Add to Album checks the puzzle and files it. Every cell needs a region, and the puzzle needs enough clues: at least 17 for an ordinary square puzzle, and at least 8 for an irregular or X one. Then, as with any import, it must have exactly one solution.
The share button (a QR code) in the title bar of the game screen, and of the slideshow, opens Share Puzzle for that game. By default it shares just the puzzle: its clues. Once you have started a game, and until you solve it, a choice appears above the QR code: The puzzle, for someone to solve from the start, or Where I am, which sends your digits and pencil marks with it, for a friend to look at where you are stuck. The QR code, Copy link and Share… all follow the choice.
The QR code is a plain sudokux4.com link, so any phone's camera can open it: in Sudoku X4 where it is installed, and otherwise in the web version. Another copy of the app can also read it with Scan QR on its Import screen. Copy link puts the same link on the clipboard, to send in a message or paste into Import.
Share… hands the same link to the device's share sheet, to send by AirDrop, Messages, Mail, Quick Share or any app that takes a link. It is not shown where there is no share sheet, as on Linux and in some browsers.