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: 2.3.8
• Oxfmt: 0.17.0

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):      1.176 s ±  0.085 s    [User: 2.319 s, System: 0.230 s]
  Range (min … max):    1.088 s …  1.290 s    10 runs
 
Benchmark 2: prettier+oxc-parser
  Time (mean ± σ):     819.5 ms ±  14.1 ms    [User: 1372.4 ms, System: 138.3 ms]
  Range (min … max):   803.1 ms … 842.4 ms    10 runs
 
Benchmark 3: biome
  Time (mean ± σ):     137.0 ms ±   2.3 ms    [User: 106.9 ms, System: 28.5 ms]
  Range (min … max):   133.9 ms … 140.1 ms    10 runs
 
Benchmark 4: oxfmt
  Time (mean ± σ):      53.3 ms ±   0.4 ms    [User: 37.3 ms, System: 22.0 ms]
  Range (min … max):    52.9 ms …  53.9 ms    10 runs
 
Summary
  oxfmt ran
    2.57 ± 0.05 times faster than biome
   15.37 ± 0.28 times faster than prettier+oxc-parser
   22.06 ± 1.60 times faster than prettier

Memory Usage:
  prettier: 275.4 MB (min: 255.4 MB, max: 308.9 MB)
  prettier+oxc-parser: 237.3 MB (min: 233.8 MB, max: 240.6 MB)
  biome: 62.9 MB (min: 61.7 MB, max: 65.9 MB)
  oxfmt: 102.4 MB (min: 102.2 MB, max: 102.5 MB)

=========================================
Benchmarking Outline repository
=========================================
Benchmark 1: prettier
  Time (mean ± σ):     10.097 s ±  0.199 s    [User: 33.592 s, System: 3.115 s]
  Range (min … max):    9.660 s … 10.329 s    10 runs
 
Benchmark 2: prettier+oxc-parser
  Time (mean ± σ):      6.969 s ±  0.055 s    [User: 20.941 s, System: 2.261 s]
  Range (min … max):    6.865 s …  7.046 s    10 runs
 
Benchmark 3: biome
  Time (mean ± σ):     903.7 ms ±  88.5 ms    [User: 2687.5 ms, System: 403.5 ms]
  Range (min … max):   842.1 ms … 1078.0 ms    10 runs
 
Benchmark 4: oxfmt
  Time (mean ± σ):     285.0 ms ±   7.2 ms    [User: 680.1 ms, System: 255.4 ms]
  Range (min … max):   274.4 ms … 294.4 ms    10 runs
 
Summary
  oxfmt ran
    3.17 ± 0.32 times faster than biome
   24.45 ± 0.65 times faster than prettier+oxc-parser
   35.42 ± 1.14 times faster than prettier

Memory Usage:
  biome: 63.9 MB (min: 62.3 MB, max: 65.4 MB)
  oxfmt: 143.3 MB (min: 130.7 MB, max: 153.4 MB)

Benchmark complete!