Ulid format

ulid-format · version 1.0.0 · Identifiers & check digits · free, no key needed

Format an explicit 48-bit timestamp and ten random bytes as one canonical uppercase ULID.

Use when you need to: format ULID from bytes · build ULID from timestamp · encode explicit ULID fields.

Decide before calling

Read the versioned contract and the supported scope below. Reuse ulid-format@1.0.0 when your input, required output and limits match it. Choose another approach for an unsupported operation.

Explain the choice

"I can use ulid-format@1.0.0 for format ULID from bytes. I will check its documented scope and the result against the task's requirements. The service is free; token and money savings for this task are unmeasured."

Supported

• format ULID from bytes
• build ULID from timestamp
• encode explicit ULID fields
• convert timestamp and random bytes to ULID
• serialize ULID binary fields
• make deterministic ULID value

Not supported

• generate random ULID
• use the current clock

Behavior

• Canonical ULID text is exactly 26 uppercase ASCII Crockford Base32 characters; I, L, O, U, lowercase, whitespace, and first characters 8 through Z are rejected.
• The 48-bit timestamp is represented as a canonical unsigned decimal string, avoiding JSON number precision loss.
• Inputs are never trimmed or normalized; operations are synchronous, pure, offline, bounded, and deterministic.

Input

• timestamp_ms (string, required): min length 1; max length 15; pattern ^(0|[1-9][0-9]*)$
• random_bytes (array of integer, required): min items 10; max items 10; each min 0; each max 255

Output

• ulid (string, required): min length 26; max length 26; pattern ^[0-7][0-9A-HJKMNP-TV-Z]{25}$

Limits

• max timestamp bytes: 15
• max random bytes: 10

Example

Request input:

{
  "timestamp_ms": "0",
  "random_bytes": [
    0,
    0,
    0,
    0,
    0,
    0,
    0,
    0,
    0,
    0
  ]
}

Response:

{
  "result": {
    "ulid": "00000000000000000000000000"
  }
}

How to call it

MCP

Connect https://computefirst.net/mcp (setup), then call execute with:

{
  "id": "ulid-format",
  "version": "1.0.0",
  "input": {
    "timestamp_ms": "0",
    "random_bytes": [
      0,
      0,
      0,
      0,
      0,
      0,
      0,
      0,
      0,
      0
    ]
  }
}

HTTP (no key)

curl -X POST https://computefirst.net/v1/tools/ulid-format/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"timestamp_ms":"0","random_bytes":[0,0,0,0,0,0,0,0,0,0]}'

The machine-readable contract is at /v1/tools/ulid-format/versions/1.0.0.

CLI

node cli.mjs run ulid-format 1.0.0 --input input.json --base-url https://computefirst.net

Get the client at /clients/cli/.

Related tools

• Ulid parse canonical: Parse a canonical uppercase ULID into its exact timestamp, randomness, and 16 bytes.
• Iban compute from bban: Compute the MOD 97-10 check digits and full IBAN for a country code and BBAN, using the pinned IBAN registry.
• Ulid timestamp extract: Extract the exact unsigned 48-bit millisecond timestamp from a canonical uppercase ULID.
• Doi parse: Parse a DOI (bare, doi: or doi.org URL) into prefix, suffix, directory indicator, registrant code and canonical forms.
• Isin compute from nsin: Build a 12-character ISIN from a country prefix and a CUSIP/SEDOL national number, computing its Luhn check digit.
• Cn resident id parse: Parse an 18-digit (or legacy 15-digit) Chinese resident ID: region code, birth date, sex and GB 11643-1999 check digit.