UUID Generator (v4, v7, v1)
Generate UUIDs: random v4, time-ordered v7, time-based v1, plus nil and max. GUID, no-hyphen, braces and URN formats, with a decoder for version and timestamp.
A UUID is a 128-bit identifier written as 32 hex digits in five hyphen-separated groups. This tool generates the versions people actually use — random v4, time-ordered v7 and time-based v1 — and can decode any UUID to show its version, variant and embedded timestamp.
How to use this tool
- Choose Generate or Decode.
- Pick a version: v4 for pure randomness, v7 when you want database-friendly sortable IDs, v1 for legacy systems.
- Set how many to make and the output format.
- To decode, paste a UUID and read its version and time.
Formula
v4 fills all bits randomly except the version (4) and variant (10) markers. v7 puts a 48-bit Unix-millisecond timestamp first, then a monotonic counter and random bits, so IDs sort by creation time.
Randomness comes from crypto.getRandomValues, the browser's cryptographically secure generator. v1 here uses a random node identifier, not your network card, so it leaks no hardware address.
Example
Decoding the RFC 9562 sample 017F22E2-79B0-7CC3-98C4-DC0C0C07398F reports version 7 and a timestamp of 2022-02-22T19:22:22Z, read straight from its first 48 bits.
Frequently asked questions
v4 or v7?
Use v7 for primary keys: it sorts by time, which keeps database indexes tidy, while still being practically unique. Use v4 when you want no time information at all.
Are these unique?
v4 draws 122 random bits, so a collision is astronomically unlikely. v7 adds a timestamp and a per-millisecond counter to avoid duplicates generated in the same instant.
What are nil and max UUIDs?
The nil UUID is all zeros and the max UUID is all ones (f’s). They are special constants used as placeholders or sentinels.
Sources
Last updated:
Page address with these inputs: https://kakao.mobile/tools/uuid-generator/
Cite or embed this tool
kakaoCalc. (2026, November 8). UUID Generator (v4, v7, v1). https://kakao.mobile/tools/uuid-generator/
“UUID Generator (v4, v7, v1).” kakaoCalc, 8 Nov. 2026, kakao.mobile/tools/uuid-generator/.
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