Mosaic
Cover parts of screenshots and image pins with rectangles or a pencil, adjust mosaic and blur strength, edit rectangles, and undo freehand strokes.
Before sharing a screenshot, use mosaic to cover names, contact details, or other content you do not want to show. Cover regular areas with a rectangle and scattered content with the pencil. Choose a pixelated mosaic or a smooth blur.
Start adding mosaic
For a screenshot, select an area first. On an image pin, press SpaceSpace to show the annotation toolbar.
Click “Mosaic,” or press the default shortcut Shift+7⇧ Shift+7. If the button is in a grouped menu, click the small arrow next to the tool to expand it.
Choose “Rectangle” or “Pencil” in the style bar below, then choose “Mosaic” or “Blur” from the “Mosaic mode” dropdown.
Hold the left mouse button and drag over the content to process. Release to finish that area. Drag again to cover other locations.
Creating mosaic requires dragging. A single click does not leave a dot as the pencil tool does.
Choose how to cover the content
Rectangle works well for a line of contact details, a table cell, or a whole block of information. Drag from one corner to the opposite corner to apply the selected effect throughout the rectangle. The pencil width control is disabled; the rectangle's dimensions determine coverage.
Pencil works well for scattered or irregular content. Set the width, then drag along the target. If one stroke does not cover everything, release and continue elsewhere. This is the default method.
While drawing with the pencil, hold Shift⇧ Shift to make the current segment straight. Its angle follows the pencil's Shift setting, useful for drawing straight across a line of text.
Choose an effect and adjust its strength
The coverage method determines where to process; the effect mode determines how it looks. Both rectangles and pencil strokes support these effects:
| Effect | Image change |
|---|---|
| Mosaic | Turns the area into pixel blocks; higher strength makes the blocks larger |
| Blur | Smooths details in the area; higher strength blurs outlines further |
- Mosaic · weakerSmaller pixel blocks
- Mosaic · strongerLarger pixel blocks
- Blur · weakerOutlines still visible
- Blur · strongerLess visible detail
Drag the slider to the right of the mode dropdown: right increases strength and left decreases it. Each effect remembers its own strength, so switching modes does not require setting it again.
Pencil width and effect strength are independent: width determines how wide a stroke is; strength determines how much the covered area is processed. Widen the pencil to cover more at once. Adjust the strength slider for larger blocks or more blur within the same area.
The scroll wheel also offers quick adjustment: in pencil mode it changes stroke width; in rectangle mode it changes effect strength. If scrolling over the image has no effect, check “Disable mouse wheel to adjust annotation tools” in the “Annotation” settings.
Change an existing area
Rectangles and freehand strokes are edited differently. A rectangle retains an adjustable area. A freehand stroke ends when you release the mouse and cannot be selected again and moved.
- Rectangle: edit againDrag inside to move; drag square handles to resize
- Pencil: undo and redrawA finished stroke cannot be selected and moved
Rectangle: select and adjust
Keep “Mosaic” selected, choose “Rectangle,” then click an existing rectangle. Square control points appear at its corners and edges.
| Adjustment | How |
|---|---|
| Position | Drag inside the rectangle |
| Coverage | Drag the square control points at the corners or edges |
| Effect and strength | Switch between “Mosaic” and “Blur” in the style bar, or drag the strength slider |
| Delete this area | Select it, then press DeleteBackspace |
If you cannot select it again, set “Mark secondary editing” to “Enable.” Rounded corners and rotation work as described in Geometric shapes; this tool's coverage buttons offer only rectangle and pencil.
Pencil: undo and redraw
Once a freehand stroke is finished, you cannot select it again to change its width, strength, or position. If it is wrong, press Ctrl+Z⌘ Command+Z to undo, set the parameters, and redraw. Add another stroke over any missed spots.
Cover separate locations with separate strokes, releasing the mouse after each. This makes it easier to preserve other areas when undoing. See Annotation basics for more on undo, redo, and annotation management.
Before copying or saving, check coverage and the result again, especially both ends of a line of text and rectangle edges. After moving a rectangle, also check that the original content is still covered.
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