UUID Generating Full Guide: v4, v7, Collisions and Misuse
When you need an ID for orders, files, microservices, etc., you often generate UUID. Choose v4 or v7, do you repeat, do you think you can be an API key, but you're always confused. This guidance removes random, orderly and safe boundaries by the use of identifiers and works against the real options of the KiloCell local generator.
The core sentence.
UUID addresses "who is the only person" and not "who is the secret" . v4 is pure random, v7/ULID is time-bound and is indexed in an orderly manner, but neither should replace a password or signature token.
Yes. UUID/ULID Generators Selective type, case/decree hyphenation and mass (from 1 to 1000).
1. What are the three types appropriate for each of them?
Tools provide three types of tools (achievement of use) crypto.getRandomValues Waiting for browser capacity:
| Type | Structure elements | Advantages | Cost / Note |
|---|---|---|---|
| UUID v4 | 128 bits, version fixed with variant, remaining random | Do not disclose the generation time, make it easy | Random insertion of primary key may exacerbate the B-Tree page split |
| UUID v7 | Prefix millisecond time, left random, version number 7 | It's roughly time-sequenced, it's good for writing and time-scrambling. | Generate a timescale from an ID |
| ULID | 128 Bit semantic, Crockford Base32, constant 26 characters | Short, Sortable, URL friendly | Encoding differs from UUID text form; Case Policy by Options |
don't wantThe string "Looks like UUID" is used as the same version: 13 hexadecimal semi-bytes (remove hyphenated version) to distinguish v4/v7 etc. An explicit agreed version of the business validation should be made.
Collisions: theory and engineering
v4 is a valid random biting of about 122 bits. Under the birthday paradox, the probability of collision becomes anxiety only when the amount of the astronomical magnitude generated. For the vast majority of Internet operations:
- Application level still recommendedThe only constraint on ID rows in the database - defense is for bugs, error imports, multiple generator sets that are inconsistent, not just mathematical collisions.
- Same msw mass v7 (b) Still based on random segments; The only index that is not to be removed is "because it probably won't hit."
- Distributive MultimachineIt is possible to use each of the random sources of passwords; No central call, unless you have business serial number requirements.
Very rare collisions can be used as keys. The attackers guessedWhether predictability and entropy are enough secretsNot waiting for birthday crashes.
3. Non-security tokens: most common misuse
| Misuse | Why is it dangerous? | More appropriate approaches |
|---|---|---|
| Use v4 as the only factor to reset the password link and remain valid for long periods | If links can be listed or posted, additional keys and short expiry are missing | High entropy token + Hash storage + Short TTL + One-time use |
| Put UUID as API Secret in the query string | Enter Referer, proxy log, browser history | Header, use a special key, rotate. |
| Use UUID instead of signing login sessions | Only the only source not proven | Sign Cookie / JWT, etc. |
| Considers "time hidden in UUID" as permission | v7/ULID Time Readable | Authorize service-end policy, not ID encoding |
| Client built-in UUID when payment order was not verified | Fake quotes | Service-end + status machine |
Yes.Secret Random StringTime, use password generator or the service CSPRNG generates a sufficiently long token and only has Hash. UUID generator resolves the identifier and does not resolve the authentication.
4. Output format options
| Options | Effects | Application |
|---|---|---|
| Standard lowercase | hyphen hexadecimal (ULID lowercase Base32) | Most codes and document defaults |
| Standard uppercase | Uppercase | Force uppercase legacy system |
| No hyphen | Get rid of it. - Lowercase (for UUID) |
Some filenames, compact storage; Noted interlocking with standard text |
ULID without hyphenation is a continuous character per se; Case by lower/upper processing. batch is a single ID for each row, which can be "copyed"
5. Phased operation
- Open /tools/generator/uuid-generator。
- Select in the "Identifier Type" UUID v4、UUID v7(default) or ULID。
- Select the output format (lower / upper case / no hyphen).
- Set the amount of generation 1 to 1000; Displays a large-word single bar for 1 and enters a volume text box for more than 1.
- Points Generate identifiers immediately； When needed CopyResult / AllCopy。
- ClearResult Avoids the remaining screen sharing.
Capacity boundaries
- Support: v4, v7, URID, format, batch, local generation.
- Not supported: The time stamp field with the UUID is deciphered, the V1 MAC address mode, the service end-point guarantee global monotonic (multi-square-square sequence depends on the details of the realization).
- ULID achieves page scripts; The production environment is to be aligned with the norms of the language library used and sampled separately.
6. Main key and index: why people turn to v7
When random v4 is used as the main cluster key, the new insertion is spread across the index, which may result in more split pages and cache failure - differences can be detected on the high-writing table. v7/ULID places the time in front of the sorting key and inserts it closer to the addition.
| scene | A more secure choice. | Notes |
|---|---|---|
| Open resources ID, wish not to expose level | v4 or random token | Ordered IDs may leak the business rhythm |
| High Write to Order Key | v7 or ULID, or Snowflake, etc. | Complement with the only constraint |
| Only associated, non-coalition | V4 Often enough | See storage and ORM |
| Short chains, displays to users | ULID or ordered short-coded | Watch out for sorted messages. |
(a) 16 byte UUID binary in space, with longer text; Modern hardware is often more flexible than the self-inflicted coordination costs in the branch libraries, but not the brainless replacement of all integer primary keys.
7. Real work landscape
Scene A: Microservices to the top
Generate v4 or v7 messages for each stop message_id, the only index of the consumer table. It's only for traceable, not confidential.
scene B: Upload File Temporary Name
{uuid}.pdf Avoiding conflict; The permission is still based on object storage strategy and signature URL, not on "no filename" as the only security measure (the file name can be disclosed).
Scenario C: Migration from auto-growth to UUID
Double-written or map stages generate a mass of v7, keeping the time roughly sorted and reducing the trajectories. Moves the script to a batch of 1000 to generate re-import.
Scenario D: Misplace UUID as an invitation
The invitation code requires brushing, frequency control and entropy. The site is used for the production of the video and for storage of the video. UUID can be the main internal key, with a separate external invitation code.
scene E: Log Link
Back and back, same gateway. request_id(v4 is fine) A single call. Watch out for log desensitivity, ID itself is usually left.
Scenario F: The Order of the Teaching Ratio
20 v7 and 20 v4 continuously to see if the dictionary is increasing more or less over time; The first of these is the "Big One-Clock" that explains index behaviour rather than proving "absolutely one-way clock."
9. Inventory: After generation
- Whether the only constraint on the database is added
- Whether the exposed ID accepts time-series information (v7/ULID)
- Whether to use as password or not wrongly
- Whether text format (hyphenation, case) is consistent with the correction rule
- Whether bulk import is heavy, isolated from the environment (detection/production)
- Whether the client generated ID service still verifies the attribution and status
FAQ
UUID v4 will never repeat?
The probability of collision is negligible with the correct use of CSPRNG, but the only constraint on the project is still attached. Once the re-emerge is up, priority is given to whether the code writes dead seeds and whether it uses non-encrypted seeds Math.random The blog is a video of the "fake UUD" in the blog.
Why is the tool default v7?
Many modern library keyboards want time to be orderly; Page default v7 is the product selection. If you need to hide time information, please recheck v4 on your own initiative.
ULID and UUID v7?
In order to be orderly: standard UUID form, eco-compatibility v7; Shorter Base32, API path →ULID. Teams choose only one main format to avoid mixing.
Unhyphen or UUID?
is another text for the same 128 bit. Regularity and database functions should be careful whether or not to expect a hyphen; Intense is avoided when saving binary type.
Can you generate a payment order locally?
Candidates for ID may be made, but payment status, amount, authority must be handled by the service end authority and be protected from redundancies. IID is the only one that does not amount to payment completion.
Is the browser safe?
Use this tool crypto.getRandomValues Fills a random segment (achievement is based on a page script). The ID generated on public screens is still leaking when the secret is still on the shoulder -- the secret is not on the projection.
A mass of 1,000. Can it get stuck?
Modern browsers are usually completed in a instant; A larger volume should be generated at the service end or in a dedicated script.
V1 UUID?
Not available at this page. v1 contains time and nodal information, privacy and Internet expansion are more concerned; V4/v7.
ID Design and data governance
Select the UUID version to specify its use. Database primary keys are usually concerned with collision probability, indexing order and cross-system generation; Log connection ID is also to consider whether it needs to be sorted in time; The open link is to consider whether the creation time or the scale of the business will be exposed. UUID v4 is random but unordered, v7 is more suitable for writing and searching over time, and the actual selection should be combined with database indexing, segmenting strategy and privacy requirements. In any version, UUID is not used as a certificate of entitlement, and the service needs to check the attribution of resources.
The team should also harmonize case, hyphenation, storage type and API sequence format. Writing a database can be done using a primary 16 byte or a regularized string, but the same field cannot be used to hyphenate and remove the field from the service. (a) Relocation of old systems by counting duplication, empty values and case differences before batch conversion; Use replay data to verify query, page break and log association before going online. The generator is responsible for providing candidate markings, and life cycle, withdrawal and access controls remain operational systems.
Continue reading
Generate 5 v4 and 5 v7, observe ranking differences; If you want to enter the password next, use the password generator instead of UUID.