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: 2.3.10
• Oxfmt: 0.23.0

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):      1.104 s ±  0.028 s    [User: 2.220 s, System: 0.229 s]
  Range (min … max):    1.064 s …  1.147 s    10 runs
 
Benchmark 2: prettier+oxc-parser
  Time (mean ± σ):     875.1 ms ±  57.3 ms    [User: 1431.1 ms, System: 150.6 ms]
  Range (min … max):   812.1 ms … 958.2 ms    10 runs
 
Benchmark 3: biome
  Time (mean ± σ):     137.9 ms ±   2.1 ms    [User: 108.4 ms, System: 27.2 ms]
  Range (min … max):   133.9 ms … 141.0 ms    10 runs
 
Benchmark 4: oxfmt
  Time (mean ± σ):     126.3 ms ±   2.1 ms    [User: 259.0 ms, System: 63.2 ms]
  Range (min … max):   123.7 ms … 129.3 ms    10 runs
 
Summary
  oxfmt ran
    1.09 ± 0.02 times faster than biome
    6.93 ± 0.47 times faster than prettier+oxc-parser
    8.74 ± 0.27 times faster than prettier

Memory Usage:
  prettier: 272.0 MB (min: 259.2 MB, max: 305.5 MB)
  prettier+oxc-parser: 235.8 MB (min: 232.7 MB, max: 239.7 MB)
  biome: 62.8 MB (min: 61.7 MB, max: 66.1 MB)
  oxfmt: 163.8 MB (min: 163.4 MB, max: 164.2 MB)

=========================================
Benchmarking Outline repository
=========================================
Benchmark 1: prettier
  Time (mean ± σ):     10.549 s ±  0.359 s    [User: 35.200 s, System: 3.132 s]
  Range (min … max):   10.060 s … 11.217 s    10 runs
 
Benchmark 2: prettier+oxc-parser
  Time (mean ± σ):      7.505 s ±  0.161 s    [User: 22.646 s, System: 2.428 s]
  Range (min … max):    7.150 s …  7.682 s    10 runs
 
Benchmark 3: biome
  Time (mean ± σ):     898.6 ms ±  64.6 ms    [User: 2782.4 ms, System: 407.7 ms]
  Range (min … max):   861.5 ms … 1069.9 ms    10 runs
 
Benchmark 4: oxfmt
  Time (mean ± σ):     388.9 ms ±   5.9 ms    [User: 1013.0 ms, System: 321.4 ms]
  Range (min … max):   382.4 ms … 398.4 ms    10 runs
 
Summary
  oxfmt ran
    2.31 ± 0.17 times faster than biome
   19.30 ± 0.51 times faster than prettier+oxc-parser
   27.12 ± 1.01 times faster than prettier

Memory Usage:
  biome: 65.2 MB (min: 61.5 MB, max: 68.3 MB)
  oxfmt: 204.2 MB (min: 195.7 MB, max: 214.4 MB)

Benchmark complete!