# O2 versus O3

**URL:** <https://discourse.julialang.org/t/o2-versus-o3/97015>\
**Category:** New to Julia\
**Tags:** performance\
**Created:** [April 3, 2023, 2:43pm UTC](https://discourse.julialang.org/t/o2-versus-o3/97015 "2023-04-03T14:43:12Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![Benq](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/benq/32/47075_2.png) [@Benq](https://discourse.julialang.org/u/Benq)\
**Post date:** [April 3, 2023, 2:43pm UTC](https://discourse.julialang.org/t/o2-versus-o3/97015/1 "2023-04-03T14:43:12Z")

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I was reading through [Performance Tips · The Julia Language](https://docs.julialang.org/en/v1/manual/performance-tips/#man-performance-annotations) and I noticed that the `-O` flag was not mentioned. Can the `-O` flag be used to speed up the examples in this section? If not, what’s a simple example where the `-O` flag provides a speedup? I wasn’t able to find much information about `-O` aside from [Questions about Julia Compilation Optimization Levels - #3 by Oscar\_Smith](https://discourse.julialang.org/t/questions-about-julia-compilation-optimization-levels/11296/3)