Generating UUIDs from the command line

Updated April 26, 2026 · 5 min read · by Samuel Yoo

You don’t need a website (or this one) to generate a UUID. Every modern OS ships with a tool. Here’s the cheatsheet for every common shell, plus how to bulk-generate, verify, and extract timestamps.

macOS / Linux

uuidgen (preinstalled on macOS, in util-linux on most distros)

uuidgen
# 0E6F1B8C-2C33-4F1F-9C0B-2A3D4E5F6A7B   (uppercase on macOS)

For lowercase:

uuidgen | tr 'A-Z' 'a-z'
# 0e6f1b8c-2c33-4f1f-9c0b-2a3d4e5f6a7b

Apple’s uuidgen does v4 only. GNU uuidgen (Linux) supports more:

uuidgen --random      # v4 (default)
uuidgen --time        # v1
uuidgen --md5  --namespace @url  --name "https://example.com"  # v3
uuidgen --sha1 --namespace @url  --name "https://example.com"  # v5

/proc/sys/kernel/random/uuid (Linux only)

cat /proc/sys/kernel/random/uuid

Always lowercase, always v4, no dependency on util-linux.

openssl (preinstalled almost everywhere)

openssl rand -hex 16 gives 32 random hex characters but not a valid UUID, because the version and variant bits aren’t set. Use uuidgen, /proc/sys/kernel/random/uuid or the Python one-liner instead.

python3 -c

python3 -c 'import uuid; print(uuid.uuid4())'
python3 -c 'import uuid; print(uuid.uuid7())'        # Python 3.14+
python3 -c 'import uuid; print(uuid.uuid5(uuid.NAMESPACE_URL, "https://example.com"))'

Python 3.14’s uuid7() is the easiest way to get a v7 UUID at the shell.

node -e

node -e 'console.log(crypto.randomUUID())'

Works in Node 14.17+. The crypto module is global — no require needed.

Use a UUID in a bash script

Capture it in a variable with command substitution:

id=$(uuidgen | tr 'A-Z' 'a-z')
echo "Created job $id"

For a script that has to run on both macOS and Linux, fall back to the kernel file when uuidgen is missing:

new_uuid() {
  if command -v uuidgen >/dev/null; then
    uuidgen | tr 'A-Z' 'a-z'
  else
    cat /proc/sys/kernel/random/uuid
  fi
}
id=$(new_uuid)

Windows

PowerShell

[guid]::NewGuid()
# Guid
# ----
# 0e6f1b8c-2c33-4f1f-9c0b-2a3d4e5f6a7b

To get just the string:

[guid]::NewGuid().ToString()

For uppercase / formatted:

[guid]::NewGuid().ToString("N")    # no hyphens
[guid]::NewGuid().ToString("B")    # {braces}

CMD

CMD has no built-in UUID. Use PowerShell:

powershell -Command "[guid]::NewGuid().ToString()"

Or use uuidgen.exe, see below.

uuidgen.exe (Windows SDK)

Windows has its own uuidgen.exe, but it isn’t on a standard install. It comes with the Windows SDK and Visual Studio’s C++ tools. Open a Developer Command Prompt and run:

uuidgen        :: one lowercase UUID
uuidgen -n5    :: five UUIDs

If you don’t have the SDK, PowerShell’s [guid]::NewGuid() does the same job with nothing to install.

Windows Subsystem for Linux

Same commands as Linux above. WSL ships with uuidgen in Ubuntu and most other distros.

Bulk generation

Generate N UUIDs

# 100 UUIDs, one per line
for i in $(seq 1 100); do uuidgen; done | tr 'A-Z' 'a-z'

# Faster on Linux — read from /proc directly
for i in $(seq 1 100); do cat /proc/sys/kernel/random/uuid; done

# Python — fastest for large batches
python3 -c 'import uuid; [print(uuid.uuid4()) for _ in range(10000)]'

# Node
node -e 'for(let i=0;i<10000;i++) console.log(crypto.randomUUID())'

For tens of thousands of UUIDs, the Python and Node one-liners are 10–100× faster than looping uuidgen in shell.

Generate as CSV

echo "uuid"                                  # header
python3 -c 'import uuid; [print(uuid.uuid4()) for _ in range(10000)]'

Or one line:

{ echo uuid; for i in $(seq 1 10000); do cat /proc/sys/kernel/random/uuid; done; } > uuids.csv

Generate v7 in bulk (cross-platform)

python3 -c '
import uuid
for _ in range(10000):
    print(uuid.uuid7())
'

Requires Python 3.14 or later. For older Python, install uuid-utils:

pip install uuid-utils
python3 -c 'import uuid_utils; [print(uuid_utils.uuid7()) for _ in range(10000)]'

Validation from the shell

# Test a value
echo "0e6f1b8c-2c33-4f1f-9c0b-2a3d4e5f6a7b" | grep -qE '^[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}$' && echo valid || echo invalid

# As a function
is_uuid() {
  echo "$1" | grep -qE '^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{12}$'
}
is_uuid "0e6f1b8c-..." && echo "✓"

Extracting a v7 timestamp from the shell

v7_to_time() {
  local id="$1"
  local hex="${id//-/}"            # strip hyphens
  local ts_hex="${hex:0:12}"       # first 12 hex = 48 bits = ms
  local ms=$((16#$ts_hex))
  date -u -d "@$((ms / 1000))" "+%Y-%m-%d %H:%M:%S UTC" 2>/dev/null \
    || date -u -r "$((ms / 1000))" "+%Y-%m-%d %H:%M:%S UTC"
}

v7_to_time "01928a47-3b30-7c5e-9d1a-f0b8c4a7e923"
# 2024-10-09 21:32:30 UTC

The first date form is GNU (Linux); the second (-r) is BSD (macOS). The function tries one then the other.

Aliases worth setting

In ~/.zshrc or ~/.bashrc:

alias uuid="uuidgen | tr 'A-Z' 'a-z' | tee >(pbcopy)"      # macOS — also copies to clipboard
alias uuid="cat /proc/sys/kernel/random/uuid"              # Linux

Then uuid produces a fresh UUID and (on macOS) copies it to the clipboard. Saves a remarkable amount of context-switching.

Common pitfalls

• macOS uuidgen is uppercase. Pipe through tr 'A-Z' 'a-z' if you need lowercase for cross-platform consistency.
• echo adds a newline. When piping a UUID into another tool that doesn’t tolerate trailing whitespace, use printf '%s' "$uuid".
• Don’t use $RANDOM in shell. It’s 15 bits, not cryptographically random, and trivially collidable. Use /dev/urandom or one of the methods above.

FAQ

How do I generate a UUID in bash?

Run uuidgen, which ships with macOS and comes with util-linux on most Linux desktops and servers, though minimal containers often leave it out. To save it, use id=$(uuidgen). On Linux, cat /proc/sys/kernel/random/uuid works even without uuidgen.

Why is uuidgen output uppercase on a Mac?

Apple’s uuidgen prints capital letters, while Linux versions print lowercase. Both are the same UUID. Pipe through tr 'A-Z' 'a-z' if you want lowercase everywhere.

How do I get uuidgen on Windows?

uuidgen.exe comes with the Windows SDK and runs from a Developer Command Prompt. Without the SDK, use PowerShell: [guid]::NewGuid().ToString(). In WSL, the Linux uuidgen works as usual.

Is a UUID from the command line safe to use as an ID?

Yes. uuidgen, /proc/sys/kernel/random/uuid, PowerShell, Python and Node all produce random v4 UUIDs from the system’s secure random source. Avoid building one from $RANDOM.

Cheat sheet

Try the tools

• UUID generator — instant in-browser, all versions, copy with one click
• Bulk UUID generator — generate up to 10,000 with CSV/JSON download
• UUID validator — paste, get version + timestamp