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Zig Language Formatter

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[iotools_zig_language_formatter]

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Guide

Zig Language Formatter

Paste raw Zig source and instantly get back code formatted in the canonical zig fmt style: K&R braces, 4-space indentation, trailing commas on multi-line lists, consistent spacing around operators, and tidy multi-line string blocks. No installs, no toolchain — runs entirely in your browser.

How to Use

Paste your Zig source into the input box, or drop a .zig file onto the uploader.
Pick an indentation style — 4 spaces (zig fmt default), 2 spaces, or tabs.
Toggle Add trailing commas to opt into the one-element-per-line rule for multi-line arg and field lists.
Copy the formatted output, or download it as formatted.zig.

Features

Canonical brace style – Moves dangling opening braces onto the previous line, K&R / Allman-free.
Operator spacing – Normalises spaces around =, ==, !=, <=, +, -, *, /, %, ++, **, &&, and || without breaking unary or pointer syntax.
Keyword spacing – Inserts a space after if, while, for, switch, catch, orelse, and other control-flow keywords before ( or {.
Trailing commas – Adds a comma to the last item of multi-line {}, (), and [] lists when the closing bracket sits on its own line.
Multi-line strings – Preserves \\ string continuations and indents them one level past the assignment.
Bracket validation – Flags unbalanced {}, (), [], and unterminated block comments before you ever see a compiler error.
Indent control – Choose 4 spaces, 2 spaces, or tabs depending on house style.
File or paste – Drop in a .zig file or paste directly. Output is one-click copyable and downloadable.

 FAQ

Why does Zig ship its own formatter instead of relying on conventions?

Zig treats source layout as part of the language contract. zig fmt is a normative rewriter built on the compiler's own parser, so every project on every platform produces byte-identical output. That eliminates style debates, makes diffs noise-free, and gives tooling like LSPs a stable target. Conventions documented in style guides drift across teams; a deterministic formatter does not.
What does the trailing-comma rule actually mean in Zig?

In Zig, a trailing comma on the last element of an argument list, struct field list, or array literal is a signal to zig fmt: keep this list one-element-per-line. Remove the trailing comma and zig fmt collapses the list onto a single line if it fits. This makes formatting partially author-controlled — a single comma is the difference between vertical and horizontal layout.
How are multi-line strings represented in Zig source?

Zig has no triple-quoted string. Multi-line literals are built by stacking single-line fragments that each begin with the backslash-backslash sequence at the start of the line. The leading whitespace before the fragment is part of indentation, not content, so the string value is exactly what follows the second backslash through the end of the line, joined by literal newlines.
Why use K&R brace placement specifically?

K&R style — opening brace on the same line as the construct that introduces the block — minimises vertical noise and keeps the visual eye-line from the condition to the body short. It also avoids the JavaScript-style automatic-semicolon hazard where a leading-brace alternative would have introduced an unrelated return parsing issue. Zig followed Go and Rust in standardising on this layout to keep the language's surface compact.
Is a heuristic formatter ever wrong compared to the real zig fmt?

A regex-and-segment formatter cannot match a parser-based one on edge cases — comptime blocks, generic anonymous structs, and labelled blocks have context-dependent spacing rules. For the bulk of day-to-day formatting (indentation, brace placement, operator spacing, trailing commas) the heuristic output is indistinguishable. For canonical-correct output before commit, run zig fmt locally; the in-browser tool is for quick clean-ups, code review previews, and snippets pasted into chat.