Steering Zig Fmt

# Steering Zig Fmt Source: [https://matklad.github.io/2026/05/08/steering-zig-fmt.html](https://matklad.github.io/2026/05/08/steering-zig-fmt.html) May 8, 2026Two tips on using`zig fmt`effectively\. Read this if you are writing Zig, or if you are implementing a code formatter\. For me,`zig fmt`is better than any other formatter I used:`rustfmt`, the one in IntelliJ,`deno fmt`\.`zig fmt`is steerable\. For every syntactic construct, it has several variations for how it might be laid out\. The variation used is selected by looking at what’s currently in a file\. Easier to show a pair of examples: ``` f(1, 2, 3); // -> zig fmt -> f(1, 2, 3); ``` ``` f(1, 2, 3,); // -> zig fmt -> f( 1, 2, 3, ); ``` Depending on the trailing comma, function call is formatted on a single line, or with one argument per line\. The way this plays out in practice is that you*decide*how you want to lay out the code, add a couple of`,`, hit the reformat shortcut \([, pis mine](https://matklad.github.io/2024/10/08/two-tips.html#s-1)\), and`zig fmt`does the rest\. For me, this works better than the alternative of the formatter guessing\. 90% of great formatting are blank lines between logical blocks and tasteful choice of intermediate variables, so you might as well lean into key choices, rather than eliminate them\. I know of one non\-trivial formatting customization point: columnar layout for arrays: ``` .{ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, }; ``` One would think that trailing comma would lead to a number\-per\-line layout, but, for arrays,`zig fmt`also takes note of the first line break\. In this case, the line break comes after the first three items, so we get three numbers per line, aligned: ``` .{ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, }; ``` How cool is that\! Furthermore, with judicious use of`\+\+`, you can vary the number of items per line\. When I need to pass`\-\-key``value`pairs to subprocess, I often go for formatting like this: ``` try run(&(.{ "aws", "s3", "sync", path, url } ++ .{ "--include", "*.html", "--include", "*.xml", "--metadata-directive", "REPLACE", "--cache-control", "max-age=0", })); ```