If you are using Firefox and zig build --listen is definitely running, you may be experiencing an unreasonably aggressive exponential backoff for WebSocket connection attempts, which is enabled by default and can block connection attempts for up to a minute. To disable this limit, open about:config and set the network.websocket.delay-failed-reconnects option to false.

Zig Build System

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This is the Zig Build System web interface. It allows live interaction with the build system.

The following zig build flags can expose extra features of this interface:

--time-report: collect and show statistics about the time taken to evaluate a build graph
--fuzz: enable the fuzzer for any Zig test binaries in the build graph (experimental)

Pipeline Component	CPU Time Sum across all threads of the time spent in this pipeline component	Real Time Wall-clock time elapsed between the start and end of this compilation phase	Compilation Phase
Parsing `tokenize` converts a file of Zig source code into a sequence of tokens, which are then processed by `Parse` into an Abstract Syntax Tree (AST).			File Lower Tokenization, parsing, and lowering of Zig source files to a high-level IR. Starting from module roots, every file theoretically accessible through a chain of `@import` calls is processed. Individual source files are processed serially, but different files are processed in parallel by a thread pool. The results of this phase of compilation are cached on disk per source file, meaning the time spent here is typically only relevant to "clean" builds.
AST Lowering `AstGen` converts a file's AST into a high-level SSA IR named Zig Intermediate Representation (ZIR). The resulting ZIR code is cached on disk to avoid, for instance, re-lowering all source files in the Zig standard library each time the compiler is invoked.
Semantic Analysis `Sema` interprets ZIR to perform type checking, compile-time code execution, and type resolution, collectively termed "semantic analysis". When a runtime function body is analyzed, it emits Analyzed Intermediate Representation (AIR) code to be sent to the next pipeline component. Semantic analysis is currently entirely single-threaded.			Declaration Lower Semantic analysis, code generation, and linking, at the granularity of individual declarations (as opposed to whole source files). These components are run in parallel with one another. Semantic analysis is almost always the bottleneck, as it is complex and currently can only run single-threaded. This phase completes when a work queue empties, but semantic analysis may add work by one declaration referencing another. This is the main phase of compilation, typically taking significantly longer than File Lower (even in a clean build).
Code Generation `CodeGen` converts AIR from `Sema` into machine instructions in the form of Machine Intermediate Representation (MIR). This work is usually highly parallel, since in most cases, arbitrarily many functions can be run through `CodeGen` simultaneously.
Linking `link` converts MIR from `CodeGen`, as well as global constants and variables from `Sema`, and places them in the output binary. MIR is converted to a finished sequence of real instruction bytes. When using the LLVM backend, most of this work is instead deferred to the "LLVM Emit" phase.
			LLVM Emit Only applicable when using the LLVM backend. Conversion of generated LLVM bitcode to an object file, including any optimization passes. When using LLVM, this phase of compilation is typically the slowest by a significant margin. Unfortunately, the Zig compiler implementation has essentially no control over it.
			Linker Flush Finalizing the emitted binary, and ensuring it is fully written to disk. When using LLD, this phase represents the entire linker invocation. Otherwise, the amount of work performed here is dependent on details of Zig's linker implementation for the particular output format, but typically aims to be fairly minimal.

Source Code

Zig Build System

Time Report

Fuzzer

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