msid

Minimal, monotonic, URL-safe, Client-first, reversible date-based IDs - just 7 chars for millisecond precision!

Encode any Date (or “now”) into the shortest possible, msid guarantees lexographically sortable and strictly increasing IDs when called in rapid succession string at ms, second, or day precision - and decode it back without loss.

• ms resolution (default) ~ 7 chars
• second resolution ~ 6 chars
• day resolution ~ 4 chars

📖 Examples

// Millisecond precision (default)
msid()
// encoded - UqofYU9 ~ 7 chars
// current - 2025-07-13T08:18:15.597Z
// decoded - 2025-07-13T08:18:15.597Z

// Second precision
msid({ resolution: "second" })
// encoded - 1uaruZ ~ 6 chars
// current - 2025-07-13T08:18:15.597Z
// decoded - 2025-07-13T08:18:15.000Z

// Day precision
msid({ resolution: "day" })
// encoded - 05H8 ~ 4 chars
// current - 2025-07-13T08:18:15.597Z
// decoded - 2025-07-13T00:00:00.000Z

✨ Features

• 🔢 Variable‑length Base‑N (no padding)
• 📆 Multi‑resolution: ms | second | day
• ⏳ Custom epoch: any start date (default 1970-01-01T00:00:00Z)
• 🔤 Custom alphabet: URL‑safe (0-9A-Za-z)
• 🔄 Reversible: msid(id) restores the exact instant
• 🔒 Monotonic: guarantees strictly increasing IDs when called in rapid succession, with optimized fast-path for default epoch/alphabet and fallback for custom settings

🚀 Quick Start

bun add msid
# npm install msid

Based on the input type, it will either encode a Date to a string or decode a string back to a Date.

import msid from "msid"

// Encode current time
msid() // → UqofYU9

// Encode in resolution: "ms" default
msid({ resolution: "ms" }) // → UqofYU9

// Encode in resolution: "second"
msid({ resolution: "second" }) // → 1uaruZ

// Encode in resolution: "day"
msid({ resolution: "day" }) // → 05H8

// Decode in resolution: "ms" default
msid("UqofYU9") // → 2025-07-13T08:18:15.597Z

// Decode in resolution: "second"
msid("1uaruZ") // → 2025-07-13T08:18:15.000Z

// Decode in resolution: "day"
msid("05H8") // → 2025-07-13T00:00:00.000Z

// Custom epoch
msid({ epoch: "2000-01-01T00:00:00.000Z" }) // → EBT2bwj

// Custom alphabet
msid({ alphabet: "0123456789abcdef" }) // → 19802dd03ad

🛠️ Benchmarks

Platform:      darwin
Architecture:  arm64
CPU Model:     Apple M2 Pro
CPU Cores:     12
Total Memory:  16.00 GB

Using hyperfine for benchmarking!

📝 Encode comparison (Node.js vs. Bun):

Benchmark 1: node ./test/bench.js msid
  Time (mean ± σ):     352.0 ms ±   3.7 ms    [User: 333.6 ms, System: 10.2 ms]
  Range (min … max):   347.0 ms … 366.1 ms    100 runs

Benchmark 2: bun ./test/bench.js msid
  Time (mean ± σ):     319.0 ms ±   3.8 ms    [User: 313.5 ms, System: 14.3 ms]
  Range (min … max):   312.0 ms … 329.7 ms    100 runs

Summary
  bun ./test/bench.js msid ran
    1.10 ± 0.02 times faster than node ./test/bench.js msid

📝 Decode comparison (Node.js vs. Bun):

Benchmark 1: node ./test/bench.js decode
  Time (mean ± σ):      92.7 ms ±   2.0 ms    [User: 80.4 ms, System: 6.3 ms]
  Range (min … max):    90.7 ms … 108.2 ms    100 runs

Benchmark 2: bun ./test/bench.js decode
  Time (mean ± σ):      53.4 ms ±   1.9 ms    [User: 54.1 ms, System: 9.5 ms]
  Range (min … max):    50.9 ms …  65.4 ms    100 runs

Summary
  bun ./test/bench.js decode ran
    1.74 ± 0.07 times faster than node ./test/bench.js decode

📝 MSID vs ULID encode time comparison:

Benchmark 1: node ./test/bench.js msid
  Time (mean ± σ):     352.7 ms ±   4.0 ms    [User: 334.1 ms, System: 10.4 ms]
  Range (min … max):   347.8 ms … 375.2 ms    100 runs

Benchmark 2: node ./test/bench.js ulid
  Time (mean ± σ):     358.3 ms ±   7.3 ms    [User: 342.9 ms, System: 10.0 ms]
  Range (min … max):   329.8 ms … 385.4 ms    100 runs

Summary
  node ./test/bench.js msid ran
    1.02 ± 0.02 times faster than node ./test/bench.js ulid

🔗 Related

• ULID – Universally Unique Lexicographically Sortable Identifiers
• KSUID – K-Sortable Globally Unique IDs

📄 License

MIT – LICENSE