What is a UUID and what does it look like?

UUID (Universally Unique Identifier) is a 128-bit ID formatted as 32 hex chars in 5 groups 8-4-4-4-12, e.g., 550e8400-e29b-41d4-a716-446655440000. Total 36 chars with hyphens. Version digit sits at position 14 (e.g., 4 for v4) and variant bits at position 19.

What is difference between UUID v4 and v1?

UUID v4 is random: 122 bits from crypto-secure random (crypto.randomUUID or crypto.getRandomValues) — unpredictable, best for security and distributed systems. UUID v1 is timestamp-based: 60-bit timestamp + clock sequence + node (MAC/random) — sortable by time, reveals creation time, useful for DB primary keys where you want time ordering.

How to generate UUID online with this tool?

Select version v4 or v1, set count 1-100, click orange Generate. UUIDs appear in Generated UUIDs textarea. Click Copy to copy all or Download to save as uuids.txt. Uses crypto.randomUUID() with fallback, and timestamp logic for v1 — 100% client-side.

Is this UUID generator secure and unique?

Yes. v4 uses Web Crypto API crypto.randomUUID() or crypto.getRandomValues which is cryptographically secure. Collision probability for v4 is ~1 in 2^122 — effectively zero. v1 adds timestamp + random clock/node. All generation is client-side, no server, no tracking.

Can I generate bulk UUIDs 1-100?

Yes, set count input 1-100 (clamped). Click Generate to create that many lines, each one UUID per line. Copy copies all with newline separator; Download saves as uuids.txt with one per line for import into DB, CSV, or code.

Is UUID same as GUID?

Essentially yes. GUID (Microsoft) is UUID variant — same 128-bit 8-4-4-4-12 format, same RFC 4122. Microsoft GUID historically used v4-like random. Our UUID v4 output is valid as GUID and accepted where GUID is required.

UUID Generator - Generate UUID Online Free

⚙️ Input Controls

Version: v4 • Count: 5

Count — number of UUIDs (1–100)

Version — UUID type

Format

Hyphens

v4 = crypto.randomUUID() fallback via crypto.getRandomValues • v1 = timestamp + random node/clock • RFC 4122 compliant

Orange = Generate • Ctrl+Enter to generate

📤 Generated UUIDs

Count: 0 • Chars: 0 • Size: 0 B

What is a UUID? Universally Unique Identifier Explained

A UUID (Universally Unique Identifier) — also called GUID in Microsoft ecosystems — is a 128-bit identifier formatted as 32 hexadecimal characters in five groups 8-4-4-4-12 with hyphens, totaling 36 characters, e.g., 550e8400-e29b-41d4-a716-446655440000 or uppercase 550E8400-E29B-41D4-A716-446655440000. Standardized as RFC 4122, a UUID guarantees uniqueness across space and time without a central registry — you can generate UUID online on any device and the collision chance is astronomically low. Each UUID encodes version (at character 14, the first nibble of time_hi_and_version: 1 for v1 timestamp , 4 for v4 random) and variant (at character 19, the high bits of clock_seq_hi: 8, 9, a, b for RFC 4122). Searches like uuid generator, generate uuid, uuid v4 generator, uuid v1, guid generator, random uuid, uuid maker all mean the same intent — create one or bulk unique IDs for databases, APIs, files, and distributed systems — and this single page satisfies them with both UUID v4 and UUID v1 in one click.

The idea dates to Apollo-era network computing: when systems needed to generate IDs without coordination, 128 bits (3.4×10³⁸ possibilities) provided enough entropy. UUID v4 devotes 122 bits to randomness (≈5.3×10³⁶ values), so even generating 1 billion UUIDs per second for 85 years gives ~50% chance of a single collision. UUID v1 instead combines a 60-bit timestamp (100-nanosecond intervals since 15 Oct 1582 Gregorian), a 14-bit clock sequence, and a 48-bit node (historically MAC, now random multicast with bit 1 set) — thus sortable by time and globally unique even on same machine. Our tool implements both: v4 via crypto.randomUUID() with crypto.getRandomValues() fallback for cryptographic quality, and v1 via timestamp + random node/clock to simulate time-based ordering without exposing real MAC.

UUID v4 vs v1 — Which Version Should You Generate?

Version	How It Generates	Sortable?	Contains Time/MAC?	Best For
v4 Random	122 bits via `crypto.getRandomValues` → set bits `0100` at version & `10xx` at variant	No — random shuffle	No — fully opaque & private	APIs, tokens, primary keys where you want unpredictability & security
v1 Timestamp	60-bit timestamp (ms×10000 + rand 0-9999) + 14-bit clock + 48-bit random node (multicast=1)	Yes — lexicographically ~time-ordered	Time embedded, node random not real MAC	Databases (time-ordered PK), logs, debugging where you need to know creation order

Regulatory mapping: Both are RFC 4122 compliant; uuid -v4 in Linux, uuidgen on macOS, New-Guid in PowerShell, java.util.UUID.randomUUID() and Python uuid.uuid4() all produce v4 layout matching our output. JavaScript crypto.randomUUID() is the browser standard — our fallback byte logic produces bit-identical format when the API is unavailable. Choose v4 if you need privacy and unpredictability (session IDs, public URLs, idempotency keys). Choose v1 if you need database locality — time-ordered UUIDs cluster inserts and improve B-Tree index performance versus random v4 scatter, though modern alternatives like ULID/Snowflake optimize this further.

Why Generate UUIDs? Benefits for Databases, APIs & Distributed Systems

Benefit	How UUID Helps	Who Uses It
🌐 No Coordination	Any service, browser, edge worker can mint an ID without calling a counter/DB — eliminates single-point bottleneck	Microservices, offline-first apps, mobile
🔒 Unpredictable (v4)	122 random bits via Web Crypto — not guessable like auto-increment 1,2,3… prevents enumeration	Public APIs, share links, invite codes
🧩 Merge-Safe	Two databases that both generated UUIDs can merge without PK collision — unlike integer sequences	Multi-region replication, CouchDB, CRDT
⏱️ Time-Ordered (v1)	v1 encodes timestamp — you can sort by UUID to get creation order without extra `created_at` column	Event sourcing, logs, time-series
📦 Language Agnostic	Same 36-char string works in Postgres `uuid`, MySQL `CHAR(36)`, Mongo, JS, Python, Go, Java	Full-stack teams
🛡️ Privacy-Safe Local	Our generator runs 100% client-side — IDs never leave browser, no server log, GDPR-friendly	Healthcare, fintech prototypes

Common Use Cases — When to Generate UUID v4 vs v1

Database Primary Keys: Postgres id UUID PRIMARY KEY DEFAULT gen_random_uuid() vs MySQL BINARY(16). Use v4 for sharded clusters where you want no coordination; use v1 if you want chronological index locality (though UUIDv7/ULID is even better for ordering).
API Idempotency Keys: Header Idempotency-Key: <uuid v4> for Stripe-style POST deduplication — client generates random v4, server stores 24h.
Distributed Tracing: traceId and spanId as v4 for OpenTelemetry — each request gets a fresh random UUID that never collides across services.
Filenames & Storage Keys: S3 object key uploads/550e8400-e29b-41d4-a716-446655440000.jpg — prevents overwrite and enumeration vs sequential names.
Offline-First & Sync: PouchDB/CouchDB docs use UUID _id so phones can create records offline and sync later without conflict.
Testing & Mock Data: Seed 100 UUIDs via our Count 1–100 for CSV import, Postman collection, or Jest factory.build() — bulk textarea one per line pastes directly.
Session & Invite Tokens: v4 in URL /invite/7f9c… — random and URL-safe (hex + hyphen) unlike integers that can be scraped.

Features of html-compiler.com UUID Generator (Free, Fast, Private)

Built with the same light-card language as htmlbeautifier.org, our UUID generator is minimal yet production-grade for both devs and QA:

Light Cards Input & Output: ⚙️ Input Controls card with 1–100 count and v4/v1 select, orange ✨ Generate primary button (#f97316, shadow 0 4px 12px rgba(249,115,22,.25)), and 📤 Generated UUIDs card showing 280px monospace textarea (#fbfdff → white on focus, break-all) — matches QR/Lorem generator familiarity.
UUID v4 via crypto.randomUUID() + Secure Fallback: Code path is if (crypto.randomUUID) try return crypto.randomUUID(); else crypto.getRandomValues(new Uint8Array(16)) → set bytes[6]=(bytes[6]&0x0f)|0x40 and bytes[8]=(bytes[8]&0x3f)|0x80 then format 8-4-4-4-12 hex. Cryptographically secure per Web Crypto, unlike Math.random().
UUID v1 via Timestamp: Implements BigInt(Date.now())*10000n + rand 60-bit timestamp → split into time_low, time_mid, time_hi_and_version with version 1 prefix, plus random clock_seq variant 10xx and 48-bit multicast node (|0x01) — true RFC 4122 v1 layout without exposing MAC.
Bulk 1–100 with Validation & Stats: Count input type=number min=1 max=100 clamped on Generate; empty/invalid defaults to 1. Live Input stats show Version • Count, Output stats show Count • Chars • Size via new Blob([text]).size for import sizing.
Format Controls: Toggle lowercase vs UPPERCASE and hyphens vs 32-char compact (no hyphens) for systems like compact keys or .NET Guid.ToString("N").
One-Click Copy, Download & Fullscreen: Copy via async navigator.clipboard.writeText with execCommand fallback, Download as uuids.txt (one per line, text/plain) via Blob+Object URL, ⛶ Full Screen via Fullscreen API on output card — identical to Base64/QR toolbar.
Keyboard & Error Resilient: Ctrl+Enter generates, clamped count prevents DoS (max 100), no external library, no fetch — under 10KB local JS. Clear/Randomize helpers mirror Lorem generator ergonomics.
100% Client-Side & Private: No backend, no cookie, no signup. Works offline after first load; UUIDs never leave device — safe for PII-adjacent prototypes.

How to Use — Generate UUID in 3 Steps

Step 1: Choose Count & Version

Set Count 1–100 in Input Controls — e.g., 1 for a single PK, 20 for a test CSV, 100 for bulk seeding. Pick Version: keep v4 — Random (122-bit crypto) as default for most uses (APIs, URLs), or switch to v1 — Timestamp + node if you need time-ordered debugging. Optionally set Format to UPPERCASE or strip hyphens for compact DB keys.

Step 2: Click Generate

Click orange ✨ Generate (or press Ctrl+Enter). The script validates count (clamps 1→100, rounds nan→1), loops for i < count: push(version==='v4'?uuidv4():uuidv1()) applying case/hyphen options, joins with \n, writes to 📤 Generated UUIDs, and updates stats like Count: 5 • Chars: 184 • Size: 184 B. The loop for v4 prefers native crypto.randomUUID() per iteration for speed; fallback path uses per-UUID getRandomValues(16) so each ID is independent.

Step 3: Copy or Download

Click 📋 Copy — we do navigator.clipboard.writeText(text) and show green Copied ✓ (5 UUIDs). Paste into Postgres, Mongo shell, Postman, or echo pipeline — each line is standalone. Or click orange ⬇ Download to save uuids.txt (or uuids-v1.txt/-v4) via new Blob([text],{type:'text/plain'}) + URL.createObjectURL — one UUID per line, LF terminated, ready for psql \copy or Excel import. Use ⛶ Full Screen to present 100 rows without scrolling.

UUID Format Anatomy & Comparison with Other IDs

Position	Field	Length	v4 Example	v1 Meaning
0–7	time_low	8 hex	`550e8400`	low 32 bits of timestamp
9–12	time_mid	4 hex	`e29b`	middle 16 bits of timestamp
14–17	time_hi_and_version	4 hex	`41d4` (4=version)	high 12 bits + version 1
19–22	clock_seq_hi+low	4 hex	`a716` (a=10xx variant)	clock sequence + variant
24–35	node	12 hex	`446655440000`	48-bit node (random multicast)

ID Type	Bits	Format	Sortable	Collision Risk	When to Prefer
UUID v4	122 random	36 hex + hyphens	No	negligible (2^-122)	Default for uniqueness & privacy
UUID v1	60 time + 62 rand	36 hex	Yes (by time)	Very low	When you need chronology
GUID (MS)	= UUID	Same (often braces)	No	Same as v4	.NET/Windows COM interop
ULID	128 (48 time +80 rand)	26 Crockford Base32	Yes	Very low	Shorter, sortable, URL-safe modern alt
Auto-Increment	32/64 sequential	1,2,3…	Yes	Requires coordination	Single DB, human-readable

Pro Tips, Pitfalls & Best Practices

Never use Math.random() for UUID: It has ~52 bits of entropy and is predictable — use Web Crypto crypto.randomUUID() / getRandomValues as we do. Our fallback is secure; a Math.random() UUID would fail audit.
Don’t expose v1 timestamp if privacy matters: v1 reveals generation time and pseudo node — for public URLs prefer v4 so adversaries can’t infer order or rate.
DB index trade-off: Random v4 scatters B-Tree inserts (write amplification). If you insert millions of rows with v4 PK, consider UUIDv7 or ULID, or use v1/time-ordered to keep locality — we provide v1 as lightweight alternative.
Case consistency: Postgres uuid type normalizes to lowercase; .NET prints uppercase with braces {GUID}. Our lower/upper toggle lets you match your stack before import to avoid case-sensitive string comparison bugs.
Hyphens matter in regex validation: Strict RFC regex is /^[0-9a-f]{8}-[0-9a-f]{4}-[1-5][0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/i — note version [1-5] and variant [89ab]. Compact 32-char without hyphens needs Guid.ToString("N") handling — our no-hyphen mode strips hyphens only after valid generation.
Bulk import: For 100 UUIDs into Postgres use psql -c "COPY my_table(id) FROM 'uuids.txt'" or JS ids.split('\n'); into Excel paste with Text-to-Columns disabled — each line is one cell. Use Download rather than Copy for 100 to avoid clipboard truncation.
Validate count: We clamp 1–100 to prevent accidental 10k loops that freeze tab. For >100, generate twice and concat, or use Node for(i<1e6) crypto.randomUUID() locally.

Target Keywords & Search Intent Map (SEO Authority)

We built this page to rank for the full UUID cluster — one URL, every intent, without stuffing. Copy and structure mirror the high-ranking htmlbeautifier.org pattern:

Primary Keyword	Intent	Where We Cover It
uuid generator	Tool	Title, H1, hero, Generate button, canonical /uuid-generator/
generate uuid / create uuid	Tool	Hero CTA, How-To steps, JSON-LD featureList
uuid v4 generator / random uuid	Tool	Version select v4, JS crypto.randomUUID section, FAQ
uuid v1 / guid generator	Tool	Version v1 timestamp logic, GUID equivalence table
bulk uuid generator / generate multiple uuids	Tool	Count 1–100 control, Download txt, Pro tips
online uuid generator free	Tool	Title, badges (no signup, client-side), conclusion
uuid vs guid / uuid format	Info	Anatomy table, comparison ULID/GUID

Frequently Asked Questions (FAQ)

What is a UUID and what does a UUID look like?

A UUID is a 128-bit ID displayed as 32 hex digits in five groups 8-4-4-4-12 like 550e8400-e29b-41d4-a716-446655440000 (36 chars with hyphens). Version digit is at position 14 (4 for v4, 1 for v1) and variant bits at 19 (8/9/a/b). Compact form without hyphens is 32 hex chars. UUIDs are standardized as RFC 4122 and interoperate with Microsoft GUID.

What is the difference between UUID v4 and v1? When should I use each?

v4 = 122 cryptographically random bits — unpredictable, private, not sortable. Use for public IDs, tokens, sharded PKs. Implementation: crypto.randomUUID() fallback to crypto.getRandomValues(16) with version nibble 0x40 and variant 0x80. v1 = 60-bit timestamp (100ns since 1582) + clock + node — time-ordered, reveals creation time. Use when you want chronological sorting or debugging. Our v1 uses BigInt(Date.now())*10000n + random multicast node so you get ordering without leaking MAC.

How do I generate a UUID online with this tool?

Pick Count 1–100, choose v4 or v1, optionally toggle case/hyphens, then click orange ✨ Generate. UUIDs appear line-separated in 📤 Generated UUIDs with stats Count • Chars • Size. Click 📋 Copy to copy all, or ⬇ Download for uuids.txt (RFC 4122 compliant, one per line). Shortcut Ctrl+Enter generates instantly. 100% client-side via Web Crypto.

Is the generated UUID secure and guaranteed unique?

v4 is cryptographically secure via crypto.randomUUID() / getRandomValues (not Math.random). With 122 random bits, even 1 billion UUIDs per second for decades gives <50% collision chance — practically unique. v1 adds timestamp + random clock/node, so same-millisecond collisions are avoided. No server is involved — private and GDPR-safe.

Can I generate 100 UUIDs at once for bulk import?

Yes. Set Count to 100 (max) and Generate — you get 100 lines (3,700 chars with hyphens). Copy preserves newlines for Postgres COPY, Mongo insertMany, or Excel. Download saves as UTF-8 uuids-v4.txt or uuids-v1.txt so you can cat uuids.txt | xargs or import via Python [line.strip() for line in open('uuids.txt')]. For more than 100, run Generate twice.

Is UUID the same as GUID?

Yes for practical purposes. GUID is Microsoft’s name for UUID — same 128-bit, same 8-4-4-4-12 format, same RFC 4122 variant bits. Windows Guid.NewGuid() produces UUID v4; you can paste our uuid v4 output wherever a GUID is required (C#, SQL Server UNIQUEIDENTIFIER), and vice versa — just adjust braces/case if your parser is strict.

Why are there hyphens and what is the UUID regex?

Hyphens are visual separators per RFC 4122 8-4-4-4-12 — 36 chars. Some systems store compact 32 chars (N format). Validation regex for hyphenated RFC 4122: /^[0-9a-f]{8}-[0-9a-f]{4}-[1-5][0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/i — checks version and variant. Our Format control lets you emit either form after generating valid UUID then stripping hyphens.

Does this tool use crypto.randomUUID() and work offline?

Yes. Primary path: crypto.randomUUID() native. Fallback: crypto.getRandomValues(new Uint8Array(16)) with correct version/variant bits — still secure, works in all modern browsers plus Safari. v1 computes timestamp locally. No network after first load, no signup, no watermark — offline-ready for labs and air-gapped demos.

Best UUID Generator Online Free in 2026 — Start Generating Now

Whether you are a backend engineer sharding Postgres across regions, a frontend dev minting idempotency keys for Stripe APIs, or a QA seeding 100 rows of mock data for a demo, a fast, secure UUID generator saves minutes every day. Stop wrestling with terminal uuidgen or Math.random() snippets — set Count 1–100 above, pick v4 random for privacy or v1 timestamp for ordering, hit orange ✨ Generate to fill 📤 Generated UUIDs, and hit 📋 Copy or ⬇ Download for a clean uuids.txt you can drop into psql, Postman, or insertMany. The same page ranks for uuid generator, generate uuid, uuid v4, uuid v1, guid generator, bulk uuid because it serves every intent with correct Web Crypto randomness and timestamp v1.

Bookmark html-compiler.com/uuid-generator/ — the lightweight, evergreen uuid generator, generate uuid online, random uuid, guid generator tool for 2026 and beyond. Loved for its htmlbeautifier.org-style light cards, 280px editor, bulk 1–100 and one-click Copy/Download. Explore our ecosystem: HTML Beautifier • CSS Beautifier • JS Beautifier • HTML Minifier • JSON Beautifier • Base64 Encoder • URL Encoder • HTML Compiler — all free, all client-side, no signup ever.

UUID Generator — Generate UUID Online Free