The Free UUID Generator Guide: v4, v7, ULID, GUIDs, Secrets and Passwords in Bulk
A migration needs a primary key, a test fixture needs two hundred IDs, and a new auth setup wants a signing secret. Most sites handle only one of those jobs. This page is a UUID generator, a GUID generator and a random password generator in one place: it makes version 4 and version 7 UUIDs, ULIDs, 256-bit secrets, prefixed API keys, passwords and PINs, one at a time or in batches. Below: which ID type to choose, how to get it, and what the tool does not do.
1. What a UUID Is, and the UUID vs GUID Difference
A UUID (universally unique identifier) is a 128-bit value written as 32 hexadecimal characters in five groups, 8-4-4-4-12. It lets any system create an ID on its own, with no central counter, and still be confident nobody else will create the same one. The format is defined in RFC 9562, which replaced the older RFC 4122 and added version 7.
The UUID vs GUID difference is only a name: GUID (globally unique identifier) is Microsoft’s name for the same 128-bit format, and a .NET Guid or SQL Server uniqueidentifier accepts a standard UUID string as is. Windows tools often show GUIDs uppercase inside braces; section 6 shows how to convert to that style.
Are UUIDs really unique? Not by guarantee, but by probability. A version 4 UUID carries 122 random bits (the other six mark the version and variant), so an accidental repeat is not a practical concern if the random source is good. Real collisions come from weak generators, not the format.
2. How to Generate a UUID, or a Thousand, in Four Steps
If you are wondering how to generate a UUID without opening a terminal, this is the quickest route: an online UUID generator free of sign-ups, with output ready the moment the page opens.
- Pick the type. The default is UUID v4 (random); switch to UUID v7 (time-ordered) or ULID for IDs that sort by creation time, or to a secret, key, password or PIN.
- Set how many. How many starts at five. As a bulk UUID generator, it lets you generate 1000 UUIDs for seed data: type 1000.
- Regenerate if needed. Each click draws a fresh batch.
- Copy or download. Copy all copies the list, one value per line; Download .txt saves a text file named after the type, such as
uuid4.txt.
For JSON or insert statements, pair the list with the CSV to JSON converter or the SQL formatter.
3. UUID v4 vs v7 vs ULID for Database Keys
The UUID v4 vs v7 question usually follows a problem: a table keyed on random UUIDs grows, and someone searches UUID primary key slow insert. The cause is the key itself. A B-tree index keeps keys in order, random values land all over it, and the index fragments.
UUID v4
Fully random, revealing nothing about when it was made. Use the UUID v4 generator for public IDs and anywhere order does not matter.
UUID v7
The first 48 bits are a millisecond timestamp and the rest is random, so new keys land at the end of the index. The UUID v7 generator fixes slow inserts in the standard format.
ULID
26 uppercase characters: a 10-character timestamp then 16 random ones. The ULID generator suits logs, file names and URLs.
ULID vs UUID comes down to where the ID will live. If the column is a native uuid type, choose v7: it stores in 16 bytes like any UUID. If the ID travels as text, ULID is shorter and sorts as a plain string. So when you need to generate UUID for Postgres primary key columns or seed SQL, v7 pastes straight into a uuid column.
Same-millisecond ordering is not guaranteed. v7 values and ULIDs made in the same millisecond share a timestamp and differ only in their random part, so a batch sorts across milliseconds but not strictly within one. Indexes do not mind; if you need strict creation order, keep a sequence column.
4. JWT Secrets, API Keys and 256-bit Keys
A UUID is an identifier, not a secret: part of it is fixed, and IDs end up in logs and URLs, so never sign tokens with one. For secrets, dedicated options produce raw random bytes with a Size of 16, 32 or 64 bytes (32 by default).
- How to generate a JWT secret key: RFC 7518 requires an HS256 key of at least 256 bits. As a JWT secret generator, choose Base64url secret at 32 bytes.
- 256-bit keys. A secret key generator 256 bit means 32 random bytes, here as Hex secret (64 characters) or Base64 secret. As a random hex string generator, the size sets the byte length.
- openssl rand -base64 32 online. That command prints 32 random bytes in Base64; Base64 secret at 32 bytes is the equivalent without a terminal. It is also the NextAuth secret generator you need for an
AUTH_SECRETvalue. - Base64url random string generator: Base64url swaps the two characters that clash with URLs, so the token goes in a link or cookie without escaping.
For how to generate a random API key, the API key (prefix_base62) option follows the familiar Stripe-style API key format, sk_ plus 32 letters and digits, with sk, pk, ctx or api as the prefix. A prefix makes a leaked key easy to spot in a log. Use this API key generator for test keys and seeding environments; in production, store a hash of each key rather than the key, which the hash generator can produce.
5. Random Passwords and PINs
Password offers a length of 4 to 128 characters (default 20) and lowercase, uppercase, digit and symbol sets, each character picked without bias. A line under the list estimates the bits of entropy and labels it weak, good or strong.
The fifth checkbox makes this a password generator without ambiguous characters. It removes 0 O 1 l I |, which look alike in many fonts and trip people up when a password is read aloud. It is on by default, and the strength estimate ignores it, so read that figure as slightly generous.
As a random PIN generator, Numeric PIN uses the same length slider and produces evenly distributed digits.
Is it safe to generate passwords online? It depends on what the site does with them. Here, generated values are never stored on our servers, never logged, never retained and never used for training. Put each one straight into a password manager.
6. What This UUID Generator Does Not Do
The honest gaps, and where to go instead:
- No v1, v3, v5 or NIL UUIDs. Only v4, v7 and ULID are offered; name-based v5 IDs need a UUID library in your code.
- No uppercase, braced or hyphen-free formatting. Output is always lowercase 8-4-4-4-12. For a Microsoft-style GUID, run the list through the case converter to uppercase it, then use the prefix and suffix option in line tools to wrap each line in
{and}. To strip the hyphens, paste the list into the regex tester, match-with the global flag and replace it with nothing. - No validation or decoding. It cannot check a UUID or read the timestamp in a v7 UUID or ULID; once you have the millisecond value, the timestamp converter turns it into a readable date.
- No NanoID, CUID or Snowflake IDs, and no custom alphabets or custom API key prefixes beyond the four listed.
- No hashing, signing or key pairs. It creates random values. Hash with the hash generator, and inspect tokens with the JWT decoder. RS256 or ES256 key pairs are outside this tool.
- No vault or breach check, and no rating of a password you type in.
7. Why Cortexis Is the Best Free UUID Generator
Most UUID pages do only UUIDs. Here is what is different.
Every random value in one place
UUIDs, ULIDs, secrets, API keys, passwords and PINs share one page and one set of buttons.
Large batches, no cap to fight
Ask for five or a thousand, then copy the list or download it as a text file.
Cryptographically secure randomness
Every value comes from a cryptographically secure source, with characters picked without bias.
Honest about v7 and ULID
Both sort by creation time, and we say plainly that order within one millisecond is not guaranteed.
Nothing is kept
Generated IDs, secrets and passwords are never stored on our servers, never logged, never retained and never used for training.
Free, with no account
No sign-up, no email and no daily limit.
It sits among a wider set of free developer and file tools built on the same terms: free, no account, and nothing you make is kept.
8. Frequently Asked Questions (FAQ)
How do I generate a UUID for free?
Open the tool at the top of this page and a batch of version 4 UUIDs is already waiting. Change the type or the How many box, then press Copy all or Download .txt.
Is a GUID the same as a UUID?
Yes. GUID is Microsoft's name for the same 128-bit identifier, and a standard UUID string works in a .NET Guid or SQL Server uniqueidentifier column. For the uppercase braced style, use the case converter and line tools.
Should I use UUID v4 or v7 for a primary key?
For a database primary key, v7 is usually better, because its leading timestamp keeps new rows near the end of the index. Use v4 when the ID is public and should reveal nothing about when it was created. Both fit the same column type.
Can two UUIDs ever be the same?
In theory yes, in practice no, as long as the random source is secure. Real collisions come from weak random number generators, not from the format, and every value here uses a cryptographically secure source.
Are v7 UUIDs and ULIDs generated here strictly in order?
They sort correctly across milliseconds, but values made within the same millisecond are ordered by their random part. That keeps indexes healthy but is not a strict sequence, so keep a separate sequence column if exact order matters.
How long should a JWT HS256 secret be?
At least 256 bits, which is 32 random bytes, as the JWA specification requires. Choose Base64url secret or Base64 secret at 32 bytes. Do not use a UUID as a signing secret.
Can it make uppercase or braced GUIDs, or v5 UUIDs?
Not directly. Output is always lowercase with hyphens, so uppercase it with the case converter, add braces with the prefix and suffix option in line tools, and remove hyphens with a replace in the regex tester. Version 1, 3 and 5 UUIDs are not offered.
Do you keep the passwords and secrets I generate?
No. Generated values are never stored on our servers, never logged, never retained and never used for training. Copy what you need into a password manager before you leave, because it cannot be recovered later.
Building the rest of the stack? Tidy a response with the JSON formatter, encode a payload with the Base64 encoder and decoder, test a validation pattern with the regex tester, or share a Wi-Fi password as a scannable code with the QR code generator. To learn how IDs, secrets and auth fit together, our free full-stack web development course covers it from the ground up.