strip-json-comments

Strip comments from JSON — turning JSONC (commented JSON) into something a strict parser accepts.

const std = @import("std");
const stripJsonComments = @import("strip_json_comments");

const input =
    \\{
    \\  // service port
    \\  "port": 8080,
    \\  "hosts": [ /* local only */ "localhost" ]
    \\}
;

const json = try stripJsonComments.stripJsonComments(allocator, input, .{});
defer allocator.free(json);

const parsed = try std.json.parseFromSlice(std.json.Value, allocator, json, .{});
defer parsed.deinit();

Comment markers inside string values are left untouched, including escaped quotes, so URLs like "https://example.com" survive.

Installation

Requires Zig 0.16.0.

zig fetch --save git+https://github.com/thelastbackspace/zig-strip-json-comments#v1.0.0

Then in build.zig:

const dep = b.dependency("strip_json_comments", .{ .target = target, .optimize = optimize });
exe.root_module.addImport("strip_json_comments", dep.module("strip_json_comments"));

API

stripJsonComments(allocator, json: []const u8, options: Options) ![]u8

Returns a new string with // line comments and /* */ block comments removed. Caller owns the result. Unterminated block comments are passed through unchanged.

Options

• whitespace: bool = true — replace comment characters with spaces, preserving positions and line endings (useful for error messages that reference offsets in the original). When false, comments are removed entirely.
• trailing_commas: bool = false — also strip trailing commas before } and ], producing output that strict JSON parsers accept.

Notes

• Whitespace replacement maps each Unicode code point in a comment to one space; upstream counts UTF-16 units, which differs only for astral-plane characters inside comments.
• Input is treated as bytes; UTF-8 sequences inside strings are copied verbatim.

Testing

zig build test

The suite ports upstream's test file: whitespace vs removal, comments inside strings, escaped quotes, CRLF/CR line endings, EOF comments, trailing commas, malformed comments, and a non-breaking-space round-trip through std.json.

Contributing

PRs welcome — see CONTRIBUTING.md. The CI gate (zig fmt --check, tests, build) must pass.

Credits

Behavior and the test suite follow the npm package strip-json-comments v5.0.3 (MIT, © Sindre Sorhus); the implementation is original. Zig implementation © 2026 thelastbackspace, MIT — see LICENSE.