TypeScript 5.9

Transpile, bundle, check

One native binary transpiles, bundles, rolls up declarations, and type-checks — no Node.js in the hot path.

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11 ms

zod, transpiled

3,181

tsc agrees

Numbers

Real, reproducible benchmarks. Run them yourself.

TypeScript: zod, 241 files, 1.7 MB

zlow

11 ms

esbuild

54 ms

bun

56 ms

tsc

1,591 ms

10 ms100 ms1 s

Square-root scale, interleaved rounds — 11 ms and 1,591 ms share no readable linear axis.

Command	rxjs · 251 files	zod · 241 files
`tsc --noCheck`	754 ms	1,591 ms
esbuild	49 ms	54 ms
bun (`Bun.Transpiler`)	35 ms	56 ms
`zlow build`	10 ms	11 ms

tsc 5.9.2 · esbuild 0.28.1 · bun 1.3.14. Checking (separate from build): 41 ms on zod, a 3,181/3,196 match against tsc.

API

Every command below is real: run it against the repo yourself.

zlow build src/ --out-dir dist/ --watch
zlow check src/ # type-check only
zlow bundle src/index.ts --tree-shake
zlow declarations src/index.ts --rollup

zig build

No silent wrongness: a construct zlow cannot honour is a named, located error with nothing written — never output that merely looks right. Full option-by-option support matrix: SUPPORT.md.

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