UUID / ULID Generator
Bulk generate cryptographically secure UUID v4 (Universally Unique Identifier) or ULID (Universally Unique Lexicographically Sortable Identifier) strings in your browser.
UUID v4 vs. ULID: Identifying the Best Unique Keys for Databases
Modern microservices, distributed architectures, and relational databases require unique identifiers to tag transactions, records, and events. Historically, databases relied on auto-incrementing integer IDs. However, in distributed systems, multiple nodes writing to separate nodes simultaneously cannot coordinate auto-increment states without severe bottleneck delays. To address this, developers use client-side identifier generators like UUID and ULID.
A UUID (Universally Unique Identifier) version 4 is a 128-bit value containing 32 hexadecimal digits separated by hyphens (such as 3f57e897-8d26-419d-989a-7a1e48474edd). With over 3.4 x 1038 possible variations, the collision risk is mathematically negligible, allowing safe local generation without cross-server synchronization.
What is a ULID and how does it solve UUID limitations?
While UUID v4 is incredibly robust, it has a major indexing flaw. Because UUID v4 values are completely random, they lack sorting order. When used as primary keys in clustered databases (like PostgreSQL B-Tree indexes or MySQL InnoDB tables), inserting random UUID values forces the database to regularly rewrite and rearrange index pages on disk. This causes severe index fragmentation and degrades write performance over time.
A ULID (Universally Unique Lexicographically Sortable Identifier) addresses this issue. A ULID is also a 128-bit value but splits its structure into:
- Timestamp Component (48 bits): A UNIX millisecond epoch timestamp that ensures newer ULIDs are always sorted after older ones.
- Randomness Component (80 bits): Cryptographically secure random entropy to guarantee uniqueness within that millisecond.
- Crockford's Base32 Encoding: Encodes the binary payload into a compact, URL-safe, 26-character alphanumeric string (excluding I, L, O, and U to avoid reading errors).
Comparison Table: UUID v4 vs. ULID
| Attribute | UUID v4 | ULID |
|---|---|---|
| Bit Length | 128 Bits | 128 Bits |
| Character Length | 36 Characters (with hyphens) | 26 Characters |
| Sortability | Random (Non-sortable) | Chronological (Sortable) |
| Encoding | Hexadecimal (Base 16) | Crockford's Base32 |
Frequently Asked Questions
Everything you need to know about UUID and ULID identifier generation.
→ How unique are the generated UUID v4 keys?
UUID v4 utilizes 122 bits of cryptographically secure random entropy. The total number of possible combinations is 2122 (approx 5.3 x 1036), rendering the probability of duplication mathematically negligible.
→ Why should I use a ULID instead of a standard UUID v4?
ULID houses a 48-bit timestamp prefix followed by 80 bits of random data, meaning they sort chronologically. UUID v4 is completely random, causing significant index page splitting and database write slows in high-write transactional systems.
→ Does the generation use local browser randomness?
Yes. It leverages standard secure API calls (window.crypto.getRandomValues) inside your local browser memory, ensuring your keys are never logged or cached on our servers.
→ Can I generate UUIDs without hyphens?
Yes. We support custom formatting options to strip hyphens, compressing the standard 36-character representation into a 32-character hexadecimal string.
Build High-Performance Uptime Infrastructure
Generate unique keys and monitor database operations seamlessly. Receive immediate alerts when transaction response times spike.