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: 3.7.4
• Biome: 2.3.11
• Oxfmt: 0.24.0

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 "$@" --write --experimental-cli --embedded-language-formatting=off --ignore-path=.prettierignore --no-cache --ignore-unknown
  • prettier + oxc plugin:
    • ./node_modules/.bin/prettier "$@" --write --experimental-cli --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):      1.097 s ±  0.016 s    [User: 2.217 s, System: 0.225 s]
  Range (min … max):    1.072 s …  1.119 s    10 runs
 
Benchmark 2: prettier+oxc-parser
  Time (mean ± σ):     852.3 ms ±  41.3 ms    [User: 1419.0 ms, System: 143.2 ms]
  Range (min … max):   800.5 ms … 906.4 ms    10 runs
 
Benchmark 3: biome
  Time (mean ± σ):     139.3 ms ±   3.5 ms    [User: 108.5 ms, System: 28.5 ms]
  Range (min … max):   136.0 ms … 148.1 ms    10 runs
 
Benchmark 4: oxfmt
  Time (mean ± σ):     125.7 ms ±   5.1 ms    [User: 248.5 ms, System: 65.6 ms]
  Range (min … max):   120.7 ms … 139.0 ms    10 runs
 
Summary
  oxfmt ran
    1.11 ± 0.05 times faster than biome
    6.78 ± 0.43 times faster than prettier+oxc-parser
    8.73 ± 0.38 times faster than prettier

Memory Usage:
  prettier: 274.3 MB (min: 262.0 MB, max: 292.0 MB)
  prettier+oxc-parser: 237.1 MB (min: 234.2 MB, max: 239.0 MB)
  biome: 61.9 MB (min: 61.4 MB, max: 62.5 MB)
  oxfmt: 163.7 MB (min: 163.6 MB, max: 163.9 MB)

=========================================
Benchmarking Outline repository
=========================================
Benchmark 1: prettier
  Time (mean ± σ):     10.031 s ±  0.145 s    [User: 33.422 s, System: 3.012 s]
  Range (min … max):    9.867 s … 10.247 s    10 runs
 
Benchmark 2: prettier+oxc-parser
  Time (mean ± σ):      7.126 s ±  0.090 s    [User: 21.381 s, System: 2.331 s]
  Range (min … max):    6.984 s …  7.273 s    10 runs
 
Benchmark 3: biome
  Time (mean ± σ):     863.0 ms ±   6.3 ms    [User: 2763.6 ms, System: 408.8 ms]
  Range (min … max):   855.4 ms … 875.3 ms    10 runs
 
Benchmark 4: oxfmt
  Time (mean ± σ):     387.2 ms ±  10.4 ms    [User: 1005.8 ms, System: 313.2 ms]
  Range (min … max):   376.1 ms … 408.6 ms    10 runs
 
Summary
  oxfmt ran
    2.23 ± 0.06 times faster than biome
   18.40 ± 0.55 times faster than prettier+oxc-parser
   25.91 ± 0.79 times faster than prettier

Memory Usage:
  biome: 64.8 MB (min: 62.4 MB, max: 69.7 MB)
  oxfmt: 206.3 MB (min: 198.0 MB, max: 218.2 MB)

Benchmark complete!