ULID Decoder
Decode ULIDs into millisecond timestamps, creation dates in any timezone, and 80-bit randomness parts.
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What is ULID Decoder?
ULID Decoder unpacks Universally Unique Lexicographically Sortable Identifiers. The first 10 of the 26 Crockford Base32 characters hide a 48-bit millisecond timestamp, and the last 16 carry 80 bits of randomness. Paste any ULID to instantly see when it was created and what random value it holds — entirely in your browser.
Key Benefits
- Instant timestamp extraction from any ULID
- Creation dates in 18 timezones plus ISO 8601
- Batch validation with clear per-row errors
- Randomness shown as Base32 and hex
Common Use Cases
- •Debugging when records were actually created
- •Auditing ULID-based primary keys in databases
- •Verifying ULID generators during development
- •Sorting or deduplicating identifiers by creation time
- •Forensics on logs that only store ULIDs
How to Decode a ULID
- Paste your ULIDs: Enter one ULID per line (up to 200). Lowercase input is accepted and normalized automatically.
- Pick a display timezone: Choose from 18 common timezones so creation dates render in local time. UTC ISO 8601 is always shown alongside.
- Read the decoded table: Each row shows the ULID, its creation date, the ISO timestamp, and the 80-bit randomness in hex. Invalid rows are flagged in red.
- Inspect the breakdown: The detail panel unpacks the first valid ULID into its 48-bit timestamp, 10-char time part, and 16-char random part. Copy any row with one click.
Key Features
- Extract the exact millisecond timestamp hidden in any ULID
- Show creation dates in 18 timezones plus UTC ISO 8601
- Separate the 10-char time part and 16-char random part
- Display the 80-bit randomness as a hex value
- Batch-decode up to 200 ULIDs with per-row validation
- Full Crockford Base32 checks — flags illegal characters instantly
Frequently Asked Questions
How do I find out when a ULID was created?
Paste it into the decoder. The first 10 characters of a ULID encode a 48-bit Unix timestamp in milliseconds, which the tool converts into a human-readable creation date in your chosen timezone, plus an ISO 8601 string.
Why is my ULID marked invalid?
ULIDs must be exactly 26 characters of Crockford Base32, which excludes the letters I, L, O, and U to prevent ambiguity. The first character is also limited to 0-7 because timestamps fit in 48 bits. Any other character, a wrong length, or a timestamp outside the year range 1970-9999 marks the row invalid.
Can I decode several ULIDs at once?
Yes. Paste up to 200 ULIDs, one per line (commas and semicolons also work as separators). Each row is validated independently, and the summary bar shows the valid and invalid counts.
What is the randomness part of a ULID?
The last 16 characters encode 80 bits of random data generated when the ULID was created. The decoder shows this part both as the original Base32 characters and as a 20-character hex value, which is useful for comparing identifiers or debugging generators.