JavaScript/TypeScript Formatter Benchmark

Comparing execution time and memory usage of Prettier, Biome, and Oxfmt.

Formatters

• Prettier
• Prettier + @prettier/plugin-oxc
• Biome Formatter
• Oxfmt

Versions

• Prettier: 3.6.2
• Biome: 2.3.7
• Oxfmt: 0.15.0

Setup

# Install dependencies and clone fixtures
pnpm run setup

# Run the benchmark
pnpm run bench

Notes

• Each formatter runs on the exact same codebase state (git reset between runs)
• Times include both parsing and formatting of all matched files
• Memory measurements track peak resident set size (RSS) during execution
• I intended to bench checker.ts, but it appears to be running for a very long time or stuck with 100% CPU.

Benchmark Details

• Test Data:
  • Outline repository (1925 files, ~198K lines of JS/JSX/TS/TSX code)
  • TypeScript compiler's parser.ts (~13.7K lines, single large file)
• Methodology:
  • 3 warmup runs before measurement
  • 10 benchmark runs for statistical accuracy
  • Git reset before each run to ensure identical starting conditions
  • Memory usage measured using GNU time (peak RSS)
  • Local binaries via ./node_modules/.bin/
  • prettier:
    • ./node_modules/.bin/prettier "$@" --write --experimental-cli --no-config --embedded-language-formatting=off --ignore-path=.prettierignore --no-cache --ignore-unknown
  • prettier + oxc plugin:
    • ./node_modules/.bin/prettier "$@" --write --experimental-cli --no-config --embedded-language-formatting=off --ignore-path=.prettierignore --no-cache --ignore-unknown --plugin @prettier/plugin-oxc
  • biome:
    • ./node_modules/.bin/biome format --write --files-ignore-unknown=true "$@"
  • oxfmt:
    • ./node_modules/.bin/oxfmt "$@"

Results

=========================================
Benchmarking parser.ts (single large file)
=========================================
Benchmark 1: prettier
  Time (mean ± σ):      1.148 s ±  0.062 s    [User: 2.209 s, System: 0.233 s]
  Range (min … max):    1.082 s …  1.237 s    10 runs
 
Benchmark 2: prettier+oxc-parser
  Time (mean ± σ):     789.8 ms ±  14.7 ms    [User: 1338.7 ms, System: 151.3 ms]
  Range (min … max):   775.1 ms … 826.1 ms    10 runs
 
Benchmark 3: biome
  Time (mean ± σ):     137.0 ms ±   3.2 ms    [User: 106.0 ms, System: 28.9 ms]
  Range (min … max):   133.6 ms … 142.5 ms    10 runs
 
Benchmark 4: oxfmt
  Time (mean ± σ):      54.5 ms ±   0.6 ms    [User: 39.2 ms, System: 21.0 ms]
  Range (min … max):    53.7 ms …  55.3 ms    10 runs
 
Summary
  oxfmt ran
    2.51 ± 0.06 times faster than biome
   14.49 ± 0.31 times faster than prettier+oxc-parser
   21.07 ± 1.17 times faster than prettier

Memory Usage:
  prettier: 276.1 MB (min: 264.9 MB, max: 287.8 MB)
  prettier+oxc-parser: 240.9 MB (min: 237.7 MB, max: 247.4 MB)
  biome: 63.4 MB (min: 62.0 MB, max: 65.8 MB)
  oxfmt: 102.5 MB (min: 102.5 MB, max: 102.7 MB)

=========================================
Benchmarking Outline repository
=========================================
Benchmark 1: prettier
  Time (mean ± σ):      8.889 s ±  0.114 s    [User: 30.299 s, System: 2.389 s]
  Range (min … max):    8.713 s …  9.072 s    10 runs
 
Benchmark 2: prettier+oxc-parser
  Time (mean ± σ):      5.864 s ±  0.059 s    [User: 18.357 s, System: 1.719 s]
  Range (min … max):    5.791 s …  5.976 s    10 runs
 
Benchmark 3: biome
  Time (mean ± σ):     852.9 ms ±  75.7 ms    [User: 2565.3 ms, System: 372.3 ms]
  Range (min … max):   801.5 ms … 1006.5 ms    10 runs
 
Benchmark 4: oxfmt
  Time (mean ± σ):     213.8 ms ±   1.6 ms    [User: 565.9 ms, System: 163.6 ms]
  Range (min … max):   211.3 ms … 216.1 ms    10 runs
 
Summary
  oxfmt ran
    3.99 ± 0.36 times faster than biome
   27.43 ± 0.35 times faster than prettier+oxc-parser
   41.58 ± 0.62 times faster than prettier

Memory Usage:
  prettier: 848.0 MB (min: 816.1 MB, max: 890.7 MB)
  prettier+oxc-parser: 673.1 MB (min: 655.7 MB, max: 695.0 MB)
  biome: 63.1 MB (min: 60.0 MB, max: 66.3 MB)
  oxfmt: 129.3 MB (min: 120.1 MB, max: 135.5 MB)

Benchmark complete!