ULID Generator

Tool Overview

This tool creates ULIDs. ULID means Universally Unique Lexicographically Sortable Identifier. It is a 128-bit identifier that combines time and randomness.

ULIDs solve a common database problem. Traditional IDs like auto-increment numbers do not sort by creation time. UUIDs are random and cannot be sorted. ULIDs combine both benefits. They are unique like UUIDs. They also sort by creation time naturally.

This matters for database performance. Sorting by creation time is common. With UUIDs, you need a separate timestamp column. With ULIDs, the ID itself contains the time. This reduces database work and improves query speed.

The tool is for developers, database administrators, and system architects. It helps anyone building applications that need sortable unique identifiers. Basic technical knowledge helps but the tool is easy to use.

Background & Concept Explanation

A ULID is a special type of identifier. It has two parts. The first part is a timestamp. The second part is random data. Together they create a unique string that sorts by time.

The timestamp uses 48 bits. This covers dates from 1970 to 10889. The random part uses 80 bits. This ensures uniqueness even when multiple ULIDs are created at the same millisecond.

ULIDs use Base32 encoding. This encoding uses only safe characters. It avoids letters that look similar like I and L, O and zero, U and V. This makes ULIDs safe for URLs, filenames, and manual entry.

Lexicographical sorting means alphabetical order. When you sort ULIDs as text, they automatically sort by creation time. This happens because the timestamp comes first. Later timestamps create larger strings in alphabetical order. A related operation involves generating random strings as part of a similar workflow.

People struggle with identifiers manually. Creating unique IDs by hand risks duplicates. Adding timestamps separately requires extra database columns. UUIDs solve uniqueness but break sorting. ULIDs solve both problems in one identifier.

ULIDs are commonly used in distributed systems. Multiple servers can create ULIDs independently. They will still sort correctly when combined. This is useful for microservices and cloud applications.

Database indexing benefits from ULIDs. Primary keys that sort naturally improve query performance. Range queries work better. Time-based filtering becomes simpler. No need for composite indexes on ID and timestamp.

Key Features

• One-click generation: Creates a new ULID instantly with a single button click. Uses the current time automatically. No configuration needed for basic use. Perfect for quick testing or immediate needs.
• Visual breakdown display: Shows the ULID split into timestamp and randomness parts. Color coding makes it easy to see the structure. The first 10 characters are the timestamp. The last 16 characters are random. This helps understand how ULIDs work.
• Timestamp decoding: Extracts the creation time from any ULID. Shows both the human-readable date and the Unix timestamp in milliseconds. Useful for debugging or verifying when something was created.
• Decode any ULID: Paste or type any ULID to decode it. The tool validates the format and extracts information. Works with ULIDs from any source. Helps verify ULIDs from other systems.
• Format validation: Checks if a string is a valid ULID. Verifies length is exactly 26 characters. Confirms all characters are from the Base32 alphabet. Shows clear error messages for invalid input.
• Copy to clipboard: One-click copying of the ULID string. Visual feedback confirms successful copy. Makes it easy to use the ULID in other applications or code.
• Download as file: Saves the ULID with decoded information to a text file. Includes the ULID, timestamp, date, and randomness component. Useful for documentation or sharing with team members.
• Generation history: Keeps track of the last 20 generated ULIDs. Click any history item to view its details again. Helps when you need to reference a previously created ULID.
• Cryptographically secure randomness: Uses the Web Crypto API for the random part. This provides true randomness suitable for security applications. Falls back to standard random functions when crypto is unavailable.
• URL-safe encoding: Uses Crockford's Base32 which excludes problematic characters. ULIDs work safely in URLs, filenames, and HTML attributes. No special encoding needed.
• AI insights feature: Optional analysis of ULID properties and use cases. Explains when and why to use ULIDs. Provides context about the specific ULID you generated.
• Input length validation: Shows warnings when input is incomplete. Displays character count as you type. Prevents confusion about why decoding fails.
• Case-insensitive input: Accepts ULIDs in uppercase or lowercase. Converts to uppercase automatically for processing. Makes manual entry easier.
• Clear and reset: Button to clear the current ULID and start fresh. Resets all decoded information. Useful when switching between different tasks.

Common Use Cases

Database primary keys: Use ULIDs as primary keys in database tables. They provide uniqueness and natural sorting. Queries that order by ID automatically order by creation time. This eliminates the need for separate timestamp columns for basic sorting.

Distributed system identifiers: Multiple servers can generate ULIDs independently. They will sort correctly when combined. This is essential for microservices architectures. Each service can create IDs without coordination.

Time-series data: Applications that track events over time benefit from ULIDs. Log entries, sensor readings, and transaction records sort naturally. Range queries become simpler. No need to join with timestamp tables.

API resource identifiers: REST APIs can use ULIDs for resource IDs. They are URL-safe and sortable. Clients can paginate through resources in creation order. The ID itself reveals when the resource was created. For adjacent tasks, generating GUIDs addresses a complementary step.

File naming: Use ULIDs to name uploaded files or generated documents. They avoid conflicts and maintain chronological order. The timestamp helps identify when files were created without reading metadata.

Event sourcing: Event-driven systems use ULIDs for event IDs. Events sort by creation time automatically. This simplifies replay and audit trails. The event log maintains natural ordering.

Message queue identifiers: Message brokers can use ULIDs for message IDs. Messages sort by creation time in queues. This helps with debugging and monitoring. You can see message order without additional fields.

Session management: Web applications can use ULIDs for session IDs. They are secure, unique, and sortable. Session lists show newest sessions first naturally. Helps with session administration and debugging.

Audit logs: Systems that track changes can use ULIDs for log entries. Entries sort chronologically without extra indexes. Makes it easy to find events from specific time periods.

Cross-system integration: When multiple systems need to share identifiers, ULIDs work well. They are standard format and sortable. Different systems can generate ULIDs independently. They combine correctly when merged.

How to Use This Tool (Step-by-Step)

1. Generate a new ULID: Click the "Regenerate" button. The tool creates a ULID using the current time. The ULID appears in the input field. Decoded information shows automatically in the breakdown panel.
2. View the visual breakdown: Look at the color-coded display. The first 10 characters are highlighted in one color. These represent the timestamp. The last 16 characters are in another color. These represent the random component.
3. Check the decoded information: Review the creation date and Unix timestamp. The date shows when the ULID was created. The timestamp shows milliseconds since January 1, 1970. This helps verify the time encoding.
4. Copy the ULID: Click the "Copy ULID" button or the copy icon next to the input. The ULID copies to your clipboard. A confirmation message appears. Paste it where you need it.
5. Decode an existing ULID: Paste or type a ULID into the input field. The tool validates the format automatically. If valid, decoded information appears. If invalid, an error message explains the problem.
6. Use generation history: Look at the Recent Generations panel. Click any ULID from history to view it again. The breakdown updates automatically. Useful when you need to reference a previous ULID.
7. Download ULID information: Click the "Download" button. A text file saves with the ULID and decoded data. Includes timestamp, date, and randomness component. Useful for documentation or records.
8. Get AI insights: Click "Get AI Insights" button below the breakdown. The tool analyzes the ULID and provides context. Explains use cases and properties. Helps understand when ULIDs are appropriate.
9. Clear and start fresh: Click the "Clear" button to reset everything. Removes the current ULID and decoded data. Prepares for a new generation or decode operation.

Calculations & Logic

ULID generation starts with the current time in milliseconds. This is the Unix timestamp. The tool converts this number to Base32. Base32 uses 32 different characters. Each character represents a value from 0 to 31. When working with related formats, generating UUIDs can be a useful part of the process.

The timestamp conversion works like this. The tool divides the timestamp by 32 repeatedly. Each division gives a remainder. The remainder maps to a Base32 character. The process repeats 10 times to create 10 characters. This encodes 48 bits of time information.

The random part uses 16 bytes from a secure random source. Each byte is a number from 0 to 255. The tool takes each byte modulo 32. This gives a value from 0 to 31. This value maps to a Base32 character. Sixteen bytes create sixteen characters. This provides 80 bits of randomness.

Decoding reverses the process. The tool reads the first 10 characters. Each character maps back to a value from 0 to 31. The tool multiplies and adds these values. This reconstructs the original timestamp. The timestamp converts to a human-readable date.

Validation checks several things. The ULID must be exactly 26 characters long. Each character must be from the Base32 alphabet. The decoded timestamp must be reasonable. It cannot be too far in the past or future. This prevents invalid ULIDs from being accepted.

Base32 encoding uses these characters: 0-9 and A-Z excluding I, L, O, U. This avoids confusing characters. Zero and O look similar. One and I look similar. U and V can be confused. Removing these makes ULIDs safer for manual entry.

Lexicographical sorting works because timestamps increase over time. A later timestamp creates a larger number. In Base32, larger numbers use characters later in the alphabet. So later ULIDs sort after earlier ones alphabetically. This creates natural time-based ordering.

The randomness component ensures uniqueness. Even if two ULIDs are created in the same millisecond, the random parts differ. With 80 bits of randomness, collisions are extremely unlikely. The probability is negligible for practical purposes. In some workflows, generating barcode formats is a relevant follow-up operation.

Reference Tables or Scales

Component	Length	Bits	Purpose
Timestamp	10 characters	48 bits	Encodes creation time in milliseconds
Randomness	16 characters	80 bits	Ensures uniqueness and security
Total ULID	26 characters	128 bits	Complete identifier

Character Set	Characters	Count	Notes
Base32 Alphabet	0-9, A-H, J-K, M-N, P-T, V-W, X-Z	32	Excludes I, L, O, U for clarity
Timestamp Range	1970 to 10889	Milliseconds	Covers practical date range

Feature	ULID	UUID	Auto-increment
Uniqueness	Yes	Yes	Within database only
Sortable by time	Yes	No	Yes
Distributed generation	Yes	Yes	No
URL-safe	Yes	Yes	Yes
Contains timestamp	Yes	No	No

Tips, Limitations & Best Practices

Use ULIDs for sortable needs: Choose ULIDs when you need identifiers that sort by creation time. If sorting does not matter, UUIDs work fine. If you only need sequential numbers, auto-increment is simpler.

Understand the timestamp: The timestamp in a ULID is when it was generated, not when a record was created. If you generate a ULID in advance, the timestamp reflects generation time. Use immediately after generation for accurate timestamps.

Database indexing: ULIDs work well as primary keys. They sort naturally which helps with range queries. However, they are longer than integers. Consider storage and performance trade-offs for very large tables.

Distributed systems: ULIDs excel in distributed environments. Multiple servers can generate them independently. They combine correctly when merged. No coordination needed between servers.

URL usage: ULIDs are URL-safe by design. Use them directly in URLs without encoding. They work in REST API endpoints and query parameters. No special handling needed.

Case sensitivity: ULIDs are case-insensitive in practice. The tool accepts both uppercase and lowercase. However, standardize on uppercase for consistency. Some systems may be case-sensitive.

Validation before use: Always validate ULIDs from external sources. Check length is 26 characters. Verify all characters are from Base32 alphabet. Decode timestamp to ensure it is reasonable. For related processing needs, generating tokens handles a complementary task.

History limitations: The tool keeps only the last 20 generated ULIDs. Copy or download important ULIDs before generating many new ones. History clears when you refresh the page.

Timestamp precision: ULID timestamps have millisecond precision. Two ULIDs created in the same millisecond may not sort correctly by sub-millisecond time. This is rarely an issue in practice.

Storage considerations: ULIDs are 26 characters as strings. This is larger than 64-bit integers. Consider storage costs for very high-volume applications. The benefits may outweigh the cost.

Migration from other IDs: When migrating from UUIDs or integers, plan carefully. ULIDs cannot be converted from existing IDs. You need to generate new ULIDs and map old IDs. This requires data migration.

Display in user interfaces: ULIDs are long strings. They may not be user-friendly for display. Consider showing only part of the ULID in UIs. Use the full ULID in APIs and databases.

Collision probability: ULID collisions are extremely unlikely. With 80 bits of randomness, you can generate millions per millisecond safely. The probability of collision is negligible for practical purposes.

Time zone handling: ULID timestamps are in UTC milliseconds. Convert to local time zones when displaying dates. The tool shows dates in your local time zone automatically.

Future compatibility: ULIDs have a defined format that will not change. They are safe for long-term storage. Systems using ULIDs today will work with future systems. No migration needed.