What Does the Photoshop Paint Bucket Tool Do?

The Paint Bucket Tool in Adobe Photoshop is primarily designed to fill an area of contiguous or similar-colored pixels with a selected foreground color or predefined pattern. By evaluating pixel color values based on user-defined tolerance settings, it provides an efficient way to replace flat backgrounds, color line art, and apply textures. This guide covers the tool's core functionality, its essential settings, and the most effective ways to use it in your workflow.

The Primary Function: Color and Pattern Fills

At its core, the Paint Bucket Tool (keyboard shortcut G) automates the process of selecting and filling pixels simultaneously. Unlike standard selection tools combined with a manual fill, the Paint Bucket evaluates the exact pixel you click and immediately fills all adjacent pixels that match its color value within a specified range.

The tool operates in two main modes, selectable from the Options bar:

  • Foreground: Fills the target area with your current active foreground color.
  • Pattern: Fills the area with a repeating tile pattern chosen from your pattern library.

Key Settings That Control the Tool

To control how the Paint Bucket behaves, several critical settings can be adjusted in the top Options bar before clicking on the canvas:

  • Tolerance: Measured on a scale from 0 to 255. A low tolerance (e.g., 10) fills only pixels that are nearly identical in color to the clicked pixel. A high tolerance (e.g., 100 or more) fills a much wider range of lighter, darker, or adjacent shades.
  • Contiguous: When checked, the tool only fills matching pixels that are physically connected to the clicked area. When unchecked, it fills every pixel matching the tolerance value across the entire layer, regardless of whether they touch.
  • Anti-alias: Smooths the boundary between the filled area and the surrounding pixels, preventing jagged, pixelated edges.
  • Opacity and Blend Modes: Dictates the transparency and interaction between the newly applied fill and the existing pixels underneath.
  • All Layers: When enabled, the tool samples colors from all visible layers to determine the boundaries of the fill, allowing you to fill areas on a blank, separate layer without altering the original art.

Common Use Cases

  • Flat Coloring in Illustration: Artists frequently use the tool to lay down "flats"—base colors within clean, closed line art boundaries.
  • Quick Background Replacement: It allows for fast color changes in studio photos or product shots featuring uniform, solid-colored backdrops.
  • Pattern Application: Applying repeating textures, such as grids, fabric weaves, or paper textures, across designated segments of a design.