Insert line break in a cell

`Ctrl` + `Enter`

All hotkeys for Google Spreadsheets (Web Application)

Movement within worksheets Move one cell up, down, left, or right	`Arrow Keys`
Movement within worksheets Move one cell to the right	`Tab`
Movement within worksheets Move one cell to the left	`Shift` + `Tab`
Movement within worksheets Move to the end of the row	`End`
Movement within worksheets Go to last cell in data region	`Ctrl` + `End`
Movement within worksheets Move to the beginning of the row	`Home`
Movement within worksheets Move to the beginning of the worksheet	`Ctrl` + `Home`
Movement within worksheets Go to left-most / right-most cell in current row	`Ctrl` + `Arrow Left` / `Ctrl` + `Arrow Right`
Movement within worksheets Go to bottom-most / to-most cell in current column	`Ctrl` + `Arrow Down` / `Ctrl` + `Arrow Up`
Movement within worksheets Move to next / move to previousworksheet	`Ctrl` + `Page Down` / `Ctrl` + `Page Up`
Movement within worksheets Move one screen to the right / one screen to the left	`Alt` + `Page Down` / `Alt` + `Page Up`
Movement within worksheets Scroll to the active cell when multiple cells are selected	`Ctrl` + `Backspace`
Movement within worksheets Switch sheets	`Ctrl` + `Shift` + `Page Up` / `Page Down`
Movement within a selected range Move from top to bottom within the selected range	`Enter`
Movement within a selected range Move from bottom to top within the selected range	`Shift` + `Enter`
Movement within a selected range Move from left to right within the selected range. If cells in a single column are selected, move down.	`Tab`
Movement within a selected range Move from right to left within the selected range. If cells in a single column are selected, move up.	`Shift` + `Tab`
Entering/editing data Select the all / entire worksheet	`Ctrl` + `a`
Entering/editing data Bold the contents of the selected cell	`Ctrl` + `b`
Entering/editing data Copy the contents of the selected cell	`Ctrl` + `c`
Entering/editing data Find words or phrases within the spreadsheet	`Ctrl` + `f`
Entering/editing data Italicize the contents of the selected cell	`Ctrl` + `i`
Entering/editing data Print	`Ctrl` + `p`
Entering/editing data Copy the content of the selected cell right (used in combo with Shift + arrow)	`Ctrl` + `r`
Entering/editing data Save	`Ctrl` + `s`
Entering/editing data Underline the contents of the selected cell	`Ctrl` + `u`
Entering/editing data Paste the contents of the selected cell	`Ctrl` + `v`
Entering/editing data Cut the contents of the selected cell	`Ctrl` + `x`
Entering/editing data Redo the last action	`Ctrl` + `y`
Entering/editing data Undo the last action.	`Ctrl` + `z`
Entering/editing data Complete a cell entry and select the cell below	`Enter`
Entering/editing data Complete a cell entry and select the previous cell above	`Shift` + `Enter`
Entering/editing data Start a new line in the same cell	`Alt` + `Enter`
Entering/editing data Insert line break in a cell	`Ctrl` + `Enter`
Entering/editing data Complete a cell entry and select the next cell to the right	`Tab`
Entering/editing data Complete a cell entry and select the previous cell to the left	`Shift` + `Tab`
Entering/editing data Edit the active cell and position the insertion point at the end of the cell contents	`F2`
Entering/editing data Edit comment	`Shift` + `F2`
Entering/editing data Cancel cell entry	`Esc`
Entering/editing data Edit the active cell and then clear it, or delete the preceding character in the active cell as you edit cell contents	`Backspace`
Entering/editing data Delete the character to the right of the insertion point, or delete the selection	`Delete`
Entering/editing data Select the entire column	`Ctrl` + `Space`
Entering/editing data Select the entire row	`Shift` + `Space`
Entering/editing data Manual select	`Shift` + `Arrow Keys`
Entering/editing data Make a copy of the document	`Ctrl` + `Shift` + `s`
Entering/editing data Strikethrough formatting for the contents of the cell	`Alt` + `Shift` + `5`
Entering/editing data Apply border outline to selected cells	`Alt` + `Shift` + `&`
Entering/editing data Remove border outline from selected cells	`Alt` + `Shift` + `_`
Entering/editing data Apply or remove top border from the selected cells	`Alt` + `Shift` + `t`
Entering/editing data Apply or remove bottom border from the selected cells	`Alt` + `Shift` + `b`
Entering/editing data Apply or remove right border from the selected cells	`Alt` + `Shift` + `r`
Entering/editing data Apply or remove left border from the selected cells	`Alt` + `Shift` + `l`
Miscellaneous Shortcuts Wrap current formula in an ArrayFormula	`Ctrl` + `Shift` + `Enter`
Miscellaneous Shortcuts Insert current date into cell	`Ctrl` + `;`
Miscellaneous Shortcuts Insert current time into cell	`Ctrl` + `:`
Miscellaneous Shortcuts Open keyboard shortcuts help	`Ctrl` + `/`
Miscellaneous Shortcuts View all formulas	`Ctrl` + `'`