Gallium.jl is now deprecated. The following Julia debuggers are actively maintained:

• Juno - the official integrated development environment (IDE) for the Julia language
• Debugger.jl - the official Julia debugger
• Rebugger.jl - an expression-level debugger for Julia with a provocative command-line (REPL) user interface
• MagneticReadHead.jl - a Julia debugger based on Cassette.jl
• Infiltrator.jl - allows you to set a breakpoint in a local context, inspect local variables and the call stack, and execute arbitrary statements in the context of the current function's module

You might also enjoy:

• Traceur.jl - runs your code and tells you about any obvious performance traps
• Cthulhu.jl - descend into Julia code and see it in all its representations.