UUIDs, Unix Timestamps and Number Bases: A Practical Guide

Updated 19 October 2026 · 6 min read

Generate unique IDs safely, read and create Unix timestamps in seconds or milliseconds, and convert between binary, octal, decimal and hex.

Three kinds of value turn up constantly in databases, APIs and logs: unique identifiers, timestamps and numbers written in other bases. Each is simple once you know the conventions, and getting them wrong causes some of the most confusing bugs.

UUIDs: IDs that never clash

A UUID, also called a GUID, is a 128-bit value written as 32 hex digits in five groups, for example 3fa85f64-5717-4562-b3fc-2c963f66afa6. Separate systems can create them independently and still be practically certain they will never collide.

The UUID Generator makes version 4 UUIDs from your browser's cryptographically secure generator. You can make up to 100 at once and use Copy all to paste them into a spreadsheet or seed file.

  • Good for database keys, idempotency keys on payment and API requests, correlation IDs in logs, and upload file names.
  • Random UUIDs do not sort by creation time, which can slow inserts in some database indexes. Time-ordered formats such as UUID v7 address that.
  • They are hard to guess but are not secrets. Do not use one as a password or access token on its own.

Unix timestamps: seconds since 1970

A Unix timestamp counts seconds since 00:00:00 UTC on 1 January 1970. It is the same number everywhere in the world, which makes it easy to store, sort and compare.

TimestampDate (UTC)
01 January 1970, 00:00:00
10000000009 September 2001, 01:46:40
17356896001 January 2025, 00:00:00
214748364719 January 2038, 03:14:07
  • Seconds or milliseconds? Most APIs use seconds (10 digits), while JavaScript and Java use milliseconds (13 digits). The Timestamp Converter detects which you pasted.
  • Results show your local time with its zone, UTC, and ISO 8601 such as 2025-01-01T00:00:00.000Z, where Z means UTC.
  • Pick a date and time to get its timestamp for API queries, database filters or expiry times.
  • Systems that store timestamps as signed 32-bit integers overflow on 19 January 2038, so check older software.

Binary, octal, decimal and hex

The Number Base Converter shows a number in all four bases at once.

DecimalBinaryOctalHex
10101012A
15111117F
25511111111377FF
1024100000000002000400
  • Hex appears in web colours, memory addresses, Unicode code points and hashes. #1E90FF is red 30, green 144, blue 255.
  • Binary appears in bit flags and subnet masks: 255.255.255.0 is 24 ones followed by 8 zeros.
  • Octal appears in Unix permissions: chmod 755 means rwx for the owner and r-x for everyone else.
  • Leave out prefixes like 0x, 0b and 0o and choose the base from the menu instead.

Converting a meeting time between cities rather than a timestamp? Use the Time Zone Converter, which handles daylight saving for the date you pick.