---
name: Lasso selection
slug: lasso-selection
category: interaction
status: published
created: 2026-08-21T00:00:00.000Z
modified: 2026-08-21T00:00:00.000Z
definition: Selecting by dragging a boundary around items on a canvas, freehand
  or as a rectangle, so whatever the outline encloses becomes the selection when
  the drag ends.
aliases:
  - name: lasso tool
    source: community
  - name: marquee selection
    source: community
  - name: free form selection
    source: community
  - name: freehand select
    source: community
tags:
  - canvas
  - dragging
  - selection
relations:
  contrastWith:
    - range-select
    - marching-ants
    - brushing
  variantOf: []
  partOf: []
  seeAlso: []
implementations: []
sources:
  - title: "Wikipedia: Lasso tool"
    url: https://en.wikipedia.org/wiki/Lasso_tool
demo: inline
exhibit: false
useWhen: dragging an outline around items to select them
---

The gesture is defined by where it starts. A press on an item means move that item; a press
on empty canvas means draw a boundary, and everything the boundary catches is selected when
the pointer comes up. That one rule is what lets a canvas offer dragging and selecting with
the same button and no mode switch, and it is why the empty space between items is load
bearing rather than decoration. While the drag runs, the outline is drawn live and the items
it currently holds are previewed as selected, so the reader can adjust the boundary before
committing rather than releasing and finding out.

Strictly, the lasso is the freehand version inherited from image editors, where the pointer
trail is the outline and the shape can wrap around anything, and the rectangle is the
marquee. In interface work the two words long ago collapsed into each other, and what most
canvases actually ship is the rectangle: it is easy to aim, easy to describe, and cheap to
test items against. Be careful with the word marquee on the web, where it is also the name
of the scrolling banner element, so say rubber band or selection rectangle if the context
could go either way. The list world's equivalent is range select, which spans an ordered
sequence with Shift and a second click; a lasso is what you reach for when items have
positions rather than an order.

Three decisions separate a lasso that feels right from one that fights you. The first is
whether an item counts when the boundary merely touches it or only when the boundary fully
contains it: design tools mostly intersect, illustration tools mostly contain, and the
choice needs to be stated in the interface somewhere because guessing it is miserable.
The second is the modifiers, where holding Shift adds the new catch to the existing
selection and Alt removes it, which is what makes an irregular selection reachable in
several passes. The third is that a press on empty canvas which never travels far enough
to count as a drag should clear the selection instead of drawing a boundary of zero size,
which is the drag threshold doing its usual job.

Everything else follows from those. A lasso that reaches the edge of its container has to
autoscroll, or a canvas larger than its window can never be fully selected in one gesture.
The pointer needs capturing so the boundary survives the pointer leaving the canvas, since
people routinely overshoot. And because the whole thing is a drag, it cannot be the only
route to a multiple selection: a keyboard reader needs select all, a click plus a modified
click, or a filter that produces the same set, and the resulting count needs announcing
rather than only being drawn.