Pressing the right square bracket key (]) while the Brush tool is active increases brush size in Adobe Photoshop, and the left square bracket key ([) shrinks it on both Windows and macOS. Adding Shift to those same keys controls hardness rather than size: Shift + ] raises hardness, and Shift + [ lowers it. Because the brackets are plain character keys, the same two keys do the same job on every Photoshop desktop install, regardless of platform. The shortcut that actually changes between Windows and macOS is the one that selects the Brush tool itself, which is one of the 16 curated defaults in the Photoshop Keyboard Shortcuts reference table. Treating the bracket keys and the Brush selection row as two separate steps keeps the printed shortcut from being silently broken by a customized preset or an OS keyboard remap.
The default Photoshop keys that grow a brush
Photoshop's Brush tool responds to two plain character keys that share the same behavior on Windows and macOS. The ] key makes the brush larger each time you press it, and the [ key makes it smaller. Adding Shift to those same brackets swaps the effect from size to hardness, so Shift + ] raises hardness and Shift + [ lowers it. Pressing the brackets with Caps Lock on behaves the same way, and the steps are not configurable from the keyboard; the size increment is set under Edit > Preferences > Tools > Brush Size Increment inside the desktop application.
Each tap of a bracket jumps the brush diameter by a fixed amount. Adobe's published defaults describe the jumps as a single pixel at very small sizes and progressively larger jumps as the brush grows, which is why the brackets feel coarse for very large brushes and fine for tiny ones. If the stepped behavior is the wrong shape for the task, Photoshop offers alternative inputs that use the mouse; those are described in a later section.
Why modifier keys differ between Windows and macOS
The square bracket keys do not use Ctrl or Command, which is why they produce the same result on both operating systems. The shortcuts that do use modifiers do not always translate cleanly between platforms. The most common pattern is that a Windows Ctrl shortcut becomes a Command shortcut on macOS, but exceptions are common and Adobe documents each row independently rather than treating Ctrl as a universal stand-in for Command. The Photoshop Keyboard Shortcuts reference table is built around that rule: it stores separate Windows and macOS fields for every row instead of converting one into the other on the fly.
Photoshop also exposes three modifier names per platform. Windows rows use Ctrl, Alt, and Shift; macOS rows use Command, Option, and Shift. The page writes the names out as words rather than symbols so that the printed combination reads the same regardless of keyboard layout, font, or paste target. Keeping the platforms separate avoids the unsafe assumption that every Windows Ctrl command becomes the same command with Command on macOS.
Use the Photoshop Keyboard Shortcuts tool to confirm the brush row
The bracket keys are not part of the curated set of 16 actions the tool ships with, because the table focuses on the Brush tool's selection key rather than every brush sub-behavior. What the table does confirm is the single-letter key that activates the Brush tool in the first place, which is B on both Windows and macOS. Once you have used the table to confirm that B selects the Brush, you can immediately press ] to grow it or [ to shrink it, knowing that those two steps come from the same Adobe default documentation.
Tool cycling across the painting tools is one of the few places where the same letter can behave differently depending on a Photoshop preference. When Use Shift Key for Tool Switch is enabled under Edit > Preferences > Tools, pressing the same letter plus Shift moves through Brush, Pencil, Color Replacement, and Mixer Brush in order. When the preference is off, the Shift modifier is free for the hardness behavior described above. The reference table cannot tell you which preference is active on your install, so it never claims that a copied combination overrides local configuration.
Look up the brush shortcut step by step
- Open the Photoshop Keyboard Shortcuts tool in your browser and choose either Windows or macOS from the platform control so the modifier names match the machine where Photoshop is running.
- Type Brush into the search field. The search is case-insensitive and checks the action label, category, and key text for the selected platform, so it returns the Brush row even if you typed it in lowercase.
- Confirm that the table shows a single key (the letter B) for both Windows and macOS; the tool stores the two platform values separately and will not display the same key for one and a different key for the other unless Adobe's default itself differs.
- Click Copy on the Brush row to place the displayed key on your clipboard. The button label changes only on that row, and the page does not write to the clipboard until you click.
- Switch back to Photoshop, press the copied key to select the Brush tool, and verify that the brush icon is active in the toolbar before you press ] to grow it.
- If the bracket keys do not change the brush, open Edit > Keyboard Shortcuts inside the application and compare the current mapping with the displayed default to find any customized binding.
If you want to look up more than the curated 16 actions, the same workflow applies to any keyword you can type in the search box. Adobe's in-app dialog and the desktop shortcut PDF remain the authority for browsing every application menu, panel command, and tool variation that the curated table intentionally leaves out. For a wider default cross-reference, the Look Up Default Photoshop Shortcuts by Platform guide walks through the same search loop with a different example.
When the default key stops matching your Photoshop
Photoshop shortcuts can be customized per tool, panel menu, and application menu through Edit > Keyboard Shortcuts and Menus. A studio preset, a migrated preference file, a language-specific configuration, a plug-in, an OS-level shortcut, an accessibility utility, a keyboard remapper, or a managed workstation policy can change the key that reaches Photoshop without any visible warning in the canvas. The reference table therefore never claims that a copied combination overrides local configuration, and the page text always ends with a reminder to verify against the in-app dialog when a command fails.
Context inside Photoshop also matters. A bracket key behaves normally only when a tool can receive input; if a modal dialog is open, a text field has focus, a tool temporarily captures a modifier, or no compatible document or selection exists, the same key can trigger something else, fire nothing at all, or type a literal character into a field. Undo depth also depends on history state and the current Photoshop version, which is why the table recommends testing unfamiliar shortcuts on a noncritical duplicate document before building them into a repetitive production workflow. Saving a file is not a substitute for maintaining backups or version history.
Other ways to change brush size without the bracket keys
Three additional input methods cover the cases where the brackets are too coarse, unavailable, or simply slower than the task needs.
- Mouse wheel scroll: with the Brush tool active, scroll the mouse wheel up or down over the canvas to grow or shrink the brush diameter. Holding Alt while scrolling changes hardness instead.
- Alt + right-click drag: on Windows, hold Alt and drag the mouse right or left with the right button held to slide a live brush-size preview across the canvas. Dragging up and down changes hardness in the same gesture.
- Options bar and Brush panel: enter an exact pixel value in the size field of the Options bar or the Brush panel for situations where the stepped bracket behavior would round the wrong way.
All three alternatives can be combined with the bracket keys in a single session; Photoshop does not lock one input method out when another is used. Choosing the right one depends on whether the task needs speed, precision, or a live visual preview of the diameter change rather than a discrete step.
Quick reference: brush size and hardness defaults
The table below records the Adobe-documented keys for brush size and hardness, plus the Brush tool selection row that the curated shortcut tool confirms directly. The values come from Adobe's published desktop defaults and from the in-app Edit > Keyboard Shortcuts dialog rather than from any computed assumption about Ctrl-to-Command translation.
| Action | Windows | macOS |
|---|---|---|
| Select Brush tool | B | B |
| Increase brush size | ] | ] |
| Decrease brush size | [ | [ |
| Increase brush hardness | Shift + ] | Shift + ] |
| Decrease brush hardness | Shift + [ | Shift + [ |
| Cycle painting tools (if preference on) | Shift + letter | Shift + letter |
Two reminders belong with the table. First, the bracket keys are character keys rather than modifier shortcuts, which is why the same letters work on both platforms without a separate conversion. Second, the shift-cycling behavior shown in the last row is conditional on a Photoshop preference and is not a guaranteed default, so verify the toggle under Edit > Preferences > Tools before relying on it in a workflow.
For a portable summary, keep the Photoshop Keyboard Shortcuts page open alongside Photoshop. Switching the platform toggle in the tool whenever you move between a Windows machine and a Mac stops the single most common source of mis-copied shortcuts, and the curated 16 rows cover the file, edit, selection, view, and tool actions you will need in the same sitting.