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ULID Generator

Generate lexicographically sortable ULIDs with timestamp entropy.

ULID Generator

Runs entirely in your browser

This tool executes locally using standard browser APIs (for example window.crypto.getRandomValues or crypto.subtle where applicable). Your input is not transmitted to or stored on a ScriptPulse server. See How Calculations Work.

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What This Tool Does

  • The ULID Generator is a browser-first developer utility designed to generate Universally Unique Lexicographically Sortable Identifiers (ULID) locally. In database architecture, standard UUIDs are randomly generated (like v4), meaning they do not have chronological order. This random distribution can degrade database B-Tree index performance during high-volume inserts. ULID solves this by combining a 48-bit millisecond timestamp with 80 bits of random entropy, creating lexicographically sortable unique keys.
  • The generator operates entirely client-side. The timestamp calculations and random byte configurations are computed in browser memory using the Web Crypto API. No data is sent over the network, protecting database structures from leaks.

How It Works

  • The tool reads the current system time in milliseconds to generate the 48-bit timestamp part.
  • It generates 10 random bytes (80 bits) using browser-native `crypto.getRandomValues()`.
  • The engine encodes both the timestamp and random bytes into Crockford's Base32 alphabet.
  • It formats the value into a 26-character string, with the timestamp part positioned first.
  • The generated ULID strings are rendered in the result panel, with copy buttons enabled.

Usage

  1. Select the quantity of ULIDs you want to generate.
  2. Click the 'Generate ULIDs' button to run the local calculations.
  3. Review the generated list in the results panel.
  4. Copy the ULIDs to your clipboard for database or application integration.

Examples

  • Generating a single ULID: Outputting a 26-character sortable identifier.
  • Creating a batch of 5 ULIDs: Generating sortable keys for test inserts.
  • Verifying sort order: Comparing ULIDs generated seconds apart to check lexicographical sorting.
  • Building time-ordered transaction IDs: Creating logs parameters for staging tests.

Real-World Use Cases

  • Generating sortable database primary keys to optimize B-Tree indexing speeds.
  • Creating chronological transaction IDs to trace microservice requests by time.
  • Generating unique identifiers for log entries that need sorting by creation time.
  • Building mock objects for database staging tests.
  • Generating time-based keys for file storage directories.

Best Practices

  • Use ULIDs as primary keys for high-volume write databases to optimize insert performance.
  • Ensure different random entropy bytes are generated for every key to prevent collisions.
  • Document key formats in database schemas to maintain consistency.
  • Sync system clocks using Network Time Protocol (NTP) to maintain accurate timestamp ordering.

Common Mistakes

  • Using standard floating-point operations that lose precision, causing incorrect sorting.
  • Assuming ULIDs are completely random: the first 10 characters represent time, so they reveal when the key was created.
  • Exposing generated ULIDs in public files instead of secure configurations.
  • Ignoring clock drift: if client and server system clocks differ, sorting order may vary slightly.

Limitations

  • ULIDs are generated in transient state; reloading the page clears the workspace.
  • The generator relies on the browser's system clock; server times may differ.
  • Calculations run locally; the tool does not track database sync conflicts.

Technical Reference Guide

  • ULID Specifications: 128-bit identifiers consisting of a 48-bit timestamp and an 80-bit random entropy block.
  • Alphabet Specs: Uses Crockford's Base32 alphabet, excluding ambiguous characters (I, L, O, U) to prevent errors.
  • Sorting: Lexicographical sorting allows database indexes to allocate keys sequentially, reducing disk fragmentation.

Specifications & Standards

ULID Specification Github Repository ReferenceCrockford's Base32 Encoding Standard Reference
Browse the full Standards & References library →

FAQ

  • Is my ULID generation secure?

    Yes. All ULIDs are generated locally inside your browser memory using the Web Crypto API. No data is sent to external servers.

  • What is a ULID?

    ULID stands for Universally Unique Lexicographically Sortable Identifier. It is a 128-bit identifier that combines a millisecond timestamp with random entropy, making it sortable by creation time.

  • How random are the generated ULIDs?

    The generator uses `crypto.getRandomValues()` for the 80-bit entropy block, leveraging hardware-based entropy sources for cryptographic randomness.

  • What is Crockford's Base32 alphabet?

    It is an alphanumeric alphabet that excludes I, L, O, and U to prevent human reading errors. It is case-insensitive and safe for database configurations.

  • Why is ULID better than UUID for databases?

    Because UUID v4 is random, inserting keys fragments database indexes (like B-Trees). ULIDs are sortable, meaning database indexes allocate keys sequentially, improving write speeds.

  • What is the length of a ULID?

    A ULID is represented as a 26-character string, consisting of 10 characters for the timestamp and 16 characters for the random entropy.

  • Can I extract the timestamp from a ULID?

    Yes. The first 10 characters of the ULID represent the millisecond timestamp, allowing you to extract the exact creation time.

  • Are ULIDs case-sensitive?

    No. Crockford's Base32 is designed to be case-insensitive, though lowercase strings are standard for consistency.

  • Does the generator work offline?

    Yes. Once the page is loaded, the page assets are cached, allowing you to use all tools without an active internet connection.

  • How many bits are in a ULID?

    A ULID contains 128 bits of data: 48 bits for the timestamp and 80 bits for the random entropy.

  • Can ULIDs collide?

    The probability is virtually zero. Even if generated at the exact same millisecond, the 80 bits of random entropy provide secure collision resistance.

  • Is there a separator symbol in ULID?

    No. Unlike UUIDs, ULIDs do not contain hyphens, rendering as a single 26-character string.

Part of this Developer Hub

This utility is part of our comprehensive Authentication & Tokens Lab topic workspace.

Explore foundational guidelines, technical specifications, and other interactive utilities related to this workflow.

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