# ULID Generator

- **URL:** https://codeasystem.com/calculators/developer/ulid-generator/
- **Category:** developer
- **Description:** Generate lexicographically sortable ULIDs; Crockford base32 timestamps plus 80 bits of monotonic randomness per the spec.
- **Primary output:** Generated ULIDs: 5 lexicographically sortable ULIDs

## Inputs
- How many (name: `count`, type: number, example: 5)

## Outputs
- Generated ULIDs: 5 lexicographically sortable ULIDs
- All ULIDs (newline-separated): 01M0Q1M9DP11RXANQMWHZF3FQF
01M0Q1M9DQZTXMZRR33B726TG8
01M0Q1M9DQZTXMZRR33B726TG9
01M0Q1M9DQZTXMZRR33B726TGA
01M0Q1M9DQZTXMZRR33B726TGB
- First ULID timestamp decodes to: 2026-08-23T10:11:00.662Z (1,787,479,860,662 ms)
- Structure: 10 chars timestamp (48-bit ms) + 16 chars randomness (80-bit), Crockford base32

## Formula / methodology
```
ULID = 10 chars (48-bit ms timestamp) + 16 chars (80-bit randomness), Crockford base32
```

Every identifier packs the current epoch millisecond into its leading ten characters using Crockford base32 (alphabet 0123456789ABCDEFGHJKMNPQRSTVWXYZ; no I, L, O or U, avoiding transcription mistakes), followed by sixteen characters of cryptographically-sourced randomness.

Within the same millisecond, randomness is forced monotonically increasing, so sorting strings sorts them by creation order exactly. The first ULID’s embedded timestamp is decoded back to a human-readable date so you can verify the structure.

## Assumptions & limitations
- 48-bit timestamps cover dates until year 10895 CE.
- Monotonicity is enforced within a generation batch, not across processes.
- Charset excludes I/L/O/U per the Crockford base32 convention.

## How to use
1. **Set the count**; Up to fifty per run for fixtures or seed data.
2. **Copy the newline-separated list**; They sort correctly as plain strings; no special comparison needed.
3. **Verify via the timestamp row**; The first ULID decodes back to its creation millisecond in UTC.

## Example
Five identifiers come out sharing a timestamp prefix (same generation burst) with distinct random tails; and string order equals creation order.

Result for these inputs:

```
Generated ULIDs: 5 lexicographically sortable ULIDs
```

## About this calculator
### ULID versus UUIDv4

Both give 128-bit uniqueness, but ULIDs embed creation time up front. Database indexes stay append-friendly, logs interleave chronologically under sort, and debugging gains a free “when was this created?”; advantages UUIDv7 pursues with a different layout.

### Why Crockford base32

Human transcription drops characters that look alike. Removing I, L, O and U (and accepting lowercase input) makes ULIDs safe to read aloud or retype; a small ergonomic win that compounds across on-call shifts.

## FAQs
### Are ULIDs URL-safe?

Yes; the entire alphabet is uppercase alphanumerics with no symbols, so they drop into URLs, filenames and CSVs without escaping.

### How do I extract the timestamp myself?

Decode the first ten characters as Crockford base32; the resulting integer is epoch milliseconds. This page shows that decoded value for the first ULID automatically.

### What if two services generate ULIDs in the same millisecond?

Cross-process monotonicity is not guaranteed. Collisions remain astronomically unlikely thanks to 80 random bits, but strict global ordering needs single-writer design.

### Can existing UUID columns migrate to ULIDs?

Commonly yes: both fit in binary(16) or fixed-width character columns; many stores keep both formats side by side during migration windows.

## Related calculators
- [UUID v4 Generator](https://codeasystem.com/calculators/developer/uuid-generator/)
- [Unix Timestamp Converter](https://codeasystem.com/calculators/developer/timestamp-converter/)
- [LLM Token Counter](https://codeasystem.com/calculators/developer/llm-token-counter/)

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Last updated: 2026-08-23 · Version: 1.0.0 · [HTML version](https://codeasystem.com/calculators/developer/ulid-generator/)