Plain lines
Put one identifier on each line for fixtures, command input, spreadsheet pasting, or easy diffs. Download the same content as a text file.
Random identifiers, ready to export
Generate UUID v4 values in bulk
Choose a count from 1 to 10,000, select standard, compact, braced, or URN presentation, then copy or download lines, comma-separated text, a JSON array, or SQL VALUES rows.
Loading the UUID v4 generator…
Enable JavaScript to generate secure random UUIDs, format batches, and inspect their structure.
Random bytes with two required fields
How UUID v4 generation works
A UUID is 128 bits, or 16 octets. For version 4, RFC 9562 assigns 122 bits to random or pseudorandom data. Four bits in octet 6 are set to binary 0100 for the version, and the two highest bits in octet 8 are set to 10 for the RFC variant. Those six fixed bits explain why the random space is 122 bits rather than 128.
LiveParse obtains all sixteen starting octets from crypto.getRandomValues(), the browser Web Cryptography API, and then masks only the version and variant positions. It never substitutes Math.random(). If a secure browser random source is unavailable, generation fails visibly instead of silently weakening the output.
The standard text form has 32 hexadecimal digits in groups of 8-4-4-4-12. A generated v4 value has 4 as the first digit of group three. For the RFC variant, group four begins with 8, 9, a, or b. These visible fields identify the layout; they do not certify who generated the value.
- Total size
- 128 bits across 16 octets.
- Random payload
- 122 bits after reserving version and variant.
- Version field
- Four bits set to
0100. - RFC variant
- Two leading bits set to
10. - Standard text
xxxxxxxx-xxxx-4xxx-[89ab]xxx-xxxxxxxxxxxx
Three quick decisions
How to generate UUID v4 online
- 1
Set the batch count
Generate one UUID for a form or up to 10,000 for fixtures, seed data, test cases, and migrations. Split larger jobs so the browser and downstream tools remain responsive.
- 2
Choose presentation
Standard lowercase hyphenated text is the safest default. Compact, uppercase, braced GUID, and
urn:uuid:output represent the same underlying 128-bit values. - 3
Copy or download
Choose one value per line, comma-separated output, a valid JSON string array, or SQL row fragments. Validate the receiving schema and use parameterized queries for untrusted data.
Very low probability is not an absolute promise
UUID v4 collisions and practical uniqueness
A sound UUID v4 generator selects from a space of 2^122 possible random payloads. That enormous space makes accidental collisions extraordinarily unlikely at ordinary application volumes, but independent random choices never create a mathematical proof that two values cannot match.
Collision risk depends on total generation volume and the quality of every random source involved. Broken entropy, copied virtual-machine state, implementation bugs, deterministic test stubs, and accidental reuse can matter more than the ideal probability model. Use mature platform facilities rather than inventing a smaller or predictable random scheme.
If a duplicate could overwrite data, cross tenant boundaries, or corrupt a workflow, enforce a database unique constraint and treat a conflict as a normal error path. A UUID reduces the need for centralized allocation; it does not replace integrity constraints or operational monitoring.
What the generator guarantees
Every successful output has the UUID v4 and RFC variant bits and draws its 122-bit payload from the browser cryptography source. It does not claim knowledge of every UUID generated elsewhere.
Validate an existing UUID →One secure source, several useful shapes
Bulk UUID v4 formats for development work
JSON array
Create a syntactically valid array of quoted strings for a test fixture or request body. The surrounding API schema and business rules still need separate validation.
SQL rows
Produce parenthesized string rows as a starting point for seed data. Prefer native UUID columns and parameterized statements rather than concatenating untrusted SQL.
GUID presentation
Use uppercase or braces when a Microsoft-oriented interface asks for them. Formatting changes the string, not the version, variant, bytes, or collision properties.
Random identifier does not mean credential
Why a UUID v4 is not a secret
Secure randomness is important, but UUID v4 defines an identifier format, not an authentication protocol. It has no built-in issuer, signature, audience, scope, expiration, rotation, revocation, or proof of possession. A user who presents a record UUID must still be authenticated and authorized for that record.
Do not use a UUID as a password reset secret, API key, session credential, cryptographic nonce with protocol-specific requirements, or substitute for a signed token merely because it is difficult to guess. Choose a dedicated security design with enough entropy for its threat model and safe server-side storage and comparison.
Identifiers can also leak through URLs, logs, analytics, referrer headers, screenshots, browser history, and support messages. Treat the resource behind an ID according to its sensitivity even when the ID itself was securely generated.
- UUID v4 provides
- A standardized 128-bit identifier with 122 random payload bits.
- UUID v4 does not provide
- Authentication, authorization, integrity, expiration, or proof of origin.
- Application must provide
- Unique constraints, access control, lifecycle rules, and conflict handling.
Opacity or chronological order
UUID v4 vs UUID v7
PropertyUUID v4UUID v7
Primary payload122 random bits after version and variant.A 48-bit Unix millisecond timestamp plus 74 remaining payload bits.
Natural orderingNo creation order is encoded.Leading time supports chronological byte and standard-text ordering across milliseconds.
Time disclosureNo timestamp is intentionally stored.Anyone holding the UUID can decode its millisecond field.
Typical reason to chooseEstablished interoperability and an opaque random layout.Index locality or time-ordered event and record identifiers.
Local processing boundary
Where generated UUIDs are processed
Generated in this tab
The browser obtains random bytes and formats UUIDs locally. Generated identifiers are not posted to a LiveParse generator endpoint.
Batch work stays local
Changing case, wrappers, layout, validation, and download content is performed on the current device.
Device boundaries remain
Clipboard history, browser extensions, screen sharing, downloads, backups, and other local software are outside the page’s control.
Still validate usage
Local generation does not determine whether an identifier is safe to publish or whether the associated resource is properly protected.
Questions answered
UUID v4 generator FAQ
How many random bits are in a UUID v4?
A UUID v4 carries 122 random bits. The other six bits identify version 4 and the RFC 9562 variant, so the full identifier remains 128 bits.
Does Web Crypto guarantee that every UUID is unique?
No. Web Crypto provides the cryptographically secure random source used here, which makes accidental collisions extraordinarily unlikely when it works correctly, but no independent random generator can promise absolute uniqueness. Enforce a unique constraint and handle conflicts when duplication would matter.
How many UUID v4 values can I generate at once?
This page generates from 1 through 10,000 UUID v4 values per batch. The limit keeps browser memory, rendering, clipboard, and download work bounded.
Is a UUID v4 safe to use as a secret token?
No. A UUID is an identifier, not a password, API key, session credential, signature, or authorization check. Use a purpose-built secret-token design with suitable entropy, storage, rotation, expiration, and server-side validation.
Can a UUID v4 reveal when it was generated?
No timestamp is defined in the UUID v4 layout. Its 122 payload bits are random or pseudorandom, so a generic decoder cannot recover a creation time from the value.
Do uppercase, braces, or removed hyphens create a different UUID?
No. Those options change the text presentation of the same 128 bits. Use standard lowercase 8-4-4-4-12 text for broad interoperability unless a receiving interface explicitly requests another format.
Should I choose UUID v4 or UUID v7?
Choose v4 for an opaque random identifier without an intentional timestamp. Consider v7 when chronological ordering and database index locality are useful and exposing generation time is acceptable.
Are generated UUID v4 values uploaded?
No. Generation, formatting, validation, and export preparation happen in the current browser tab. Clipboard managers, downloaded files, extensions, and other software on your device remain separate privacy boundaries.