Drag-to-Snap Is Not Working, or Working Far Too Eagerly

Nothing happens when I drag to an edge

Work down this list in order; the first two account for most reports.

1. Snap areas are switched off. Settings → Snap Areas. They can be disabled wholesale, and an imported configuration from another machine may have them off.
2. Accessibility permission is not in force. Drag-to-snap needs the same permission as the shortcuts. If shortcuts are also dead, fix the permission first — see the full diagnostic.
3. The drag is too fast. The region has to be entered and dwelt in briefly. A quick flick to the edge often misses.
4. Native macOS tiling is also active and consuming the gesture.
5. A modifier requirement is set — if <code>snapModifiers</code> has been configured, dragging without holding that key does nothing at all.

That last one is worth checking even if you do not remember setting it, because it survives configuration imports and is invisible in the settings window:

# what is currently required?
defaults read com.knollsoft.Rectangle snapModifiers

# remove any modifier requirement, then restart the app
defaults delete com.knollsoft.Rectangle snapModifiers

It snaps when I did not want it to

The opposite complaint, and more common among people who mostly use the keyboard: windows maximise when merely being moved near the top of the screen, or jump to a half when dragged past the side.

Three graduated responses, from least to most drastic.

Narrow the trigger margin. Each edge has its own margin, defaulting to 5 pixels. Increasing the value makes the region harder to enter accidentally:

defaults write com.knollsoft.Rectangle snapEdgeMarginTop -int 20
defaults write com.knollsoft.Rectangle snapEdgeMarginBottom -int 10
defaults write com.knollsoft.Rectangle snapEdgeMarginLeft -int 10
defaults write com.knollsoft.Rectangle snapEdgeMarginRight -int 10
# restart the app for these to load

Disable individual regions. This is the precise instrument, and it is a bit field — each region has a bit index, and you sum the powers of two for the ones you want off. The top edge, which triggers maximise and is the most commonly resented, is bit 0:

# disable only the top (maximize) region
defaults write com.knollsoft.Rectangle ignoredSnapAreas -int 1

# disable the four half-regions below the corners: 256+512+1024+2048
defaults write com.knollsoft.Rectangle ignoredSnapAreas -int 3840

# disable top and bottom edges: 1+2
defaults write com.knollsoft.Rectangle ignoredSnapAreas -int 3

Require a modifier. The most decisive option: snapping only happens while a chosen key is held, so ordinary dragging never triggers anything. Values are summed if you want a combination.

# require Command to be held while dragging
defaults write com.knollsoft.Rectangle snapModifiers -int 1048576

# require Control+Shift: 262144 + 131072
defaults write com.knollsoft.Rectangle snapModifiers -int 393216

Windows dragged upward disappear into Mission Control

Dragging a window quickly toward the top of the screen sometimes triggers Mission Control instead of the maximise snap. This is a macOS gesture, not an application behaviour, and it is genuinely maddening on a laptop trackpad.

There is a setting to suppress it for fast drags while leaving slow deliberate ones alone. Once enabled, a checkbox for it also appears in the Snap Areas tab:

defaults write com.knollsoft.Rectangle missionControlDragging -int 2

# tuning: how far off-screen is tolerated (default 25 pixels)
defaults write com.knollsoft.Rectangle missionControlDraggingAllowedOffscreenDistance -float 40

# tuning: how long the suppression lasts, in milliseconds (default 250)
defaults write com.knollsoft.Rectangle missionControlDraggingDisallowedDuration -int 400

Coexisting with the built-in macOS tiling

Recent macOS versions tile windows dragged to an edge on their own. Two systems responding to the same gesture produces doubled snapping, a visible flicker, or a window that lands somewhere neither tool intended.

Pick one owner. Either disable macOS tiling in System Settings → Desktop &amp; Dock, or disable snap areas in the app and keep only the keyboard shortcuts — which is a perfectly good arrangement, since the keyboard commands do not conflict with system tiling at all. The full comparison is in the dedicated guide.

Extra regions worth enabling

One that is off by default and genuinely useful on wide displays — corner regions that produce sixths rather than quarters:

defaults write com.knollsoft.Rectangle sixthsSnapArea -bool true

Once enabled, drag to a corner and then slide along the edge toward the thirds region to reach a sixth. On a 34-inch display this makes a six-panel layout achievable by dragging, which the default regions cannot do.

The visual preview shown during a drag — the footprint — is also fully configurable: transparency, border width, colour, fade and animation. That is covered in the snap area customisation guide along with everything else in the appearance department.

Questions