# Os

Enables optimizations that do not increase code size; it produces smaller code size than O2.

## Syntax

Linux: | -Os

macOS: | -Os

Windows: | /Os

## Arguments

None

## Default

OFF | Optimizations are made for code speed. However, if O1 is specified, Os is the default.

## Description

This option enables optimizations that do not increase code size; it produces smaller code size than O2. It disables some optimizations that increase code size for a small speed benefit.

This option tells the compiler to favor transformations that reduce code size over transformations that produce maximum performance.

## IDE Equivalent

Visual Studio: Optimization > Favor Size or Speed

Eclipse: None

Xcode: None

## Alternate Options

None

Parent topic: Optimization Options

## See Also

O compiler option
Ot compiler option