# ULID

Hacker Approved page: https://hackerapproved.com/p/ulid/

11 people recommended ULID in Hacker News comments, 5 had mixed feelings and 5 criticized it, November 2025 to October 2026. It was recommended in 4 of 12 months, in 5 threads. It meets the Hacker Approved badge rule.

**Verdict:** Free spec for sortable IDs with a short string form that helps indexing and diagnostics. Critics say its monotonic mode can collide across threads.

Summary written by Claude from 31 comments. It was written before the November 2026 recount, and 30 of those comments still count.

## Why people recommend it

- Short, easy-to-select string form (3 comments in the sample): "These IDs are very important for diagnostics, and making them easily selectable is a good goal in my book." ([source](https://news.ycombinator.com/item?id=46213366)) "I can easily select them as one word, instead of various implementations of browsers, terminals, DB guis" ([source](https://news.ycombinator.com/item?id=46211515)) "I also like ULID's shorter representation." ([source](https://news.ycombinator.com/item?id=50221016))
- Low collision risk versus UUIDv7 (3 comments in the sample): "id's created within the same millisecond would be differentiated by the 80 bits of randomness (more than UUID v7" ([source](https://news.ycombinator.com/item?id=46212144)) "It's very near impossibly for there to be a conflict since the timestamp resolves at the microsecond level" ([source](https://news.ycombinator.com/item?id=46213609)) "the extra random bits (over UUID7) reduce conflict possibilities by orders of magnitude" ([source](https://news.ycombinator.com/item?id=46212879))
- Time-sortable, reduces index fragmentation (2 comments in the sample): "If you are looking for a monotonously increasing, sortable ID, you might then want to consider ULID" ([source](https://news.ycombinator.com/item?id=50218016)) "ULIDs solve database index fragmentation caused when using UUIDv4" ([source](https://news.ycombinator.com/item?id=46212737))
- Used in production for years (1 comment in the sample): "This is why ULID exists and why I use them in my ext_id columns." ([source](https://news.ycombinator.com/item?id=46276695))

## What people warn about

- Monotonic mode collides across threads (3 comments in the sample): "It's easy to shoot yourself in the foot by blindly trusting ULID will always generate a unique ID across threads without blocking your thread." ([source](https://news.ycombinator.com/item?id=46212830)) "it has a sequential ID generation mode in its spec which is prone to conflicts on multi-threads, processes or hosts" ([source](https://news.ycombinator.com/item?id=46211578)) "it must lock the sequence as it still uses a single random value" ([source](https://news.ycombinator.com/item?id=46212222))
- Randomness source left unspecified (2 comments in the sample): "I love the aesthetics. The cryptographic strength tradeoffs (against UUIDv7) seem rough for a lot of applications, though." ([source](https://news.ycombinator.com/item?id=46210871)) "the ULID spec suggests you use a CSPRNG, but doesn't mandate that or provide specific advice on appropriate algorithms" ([source](https://news.ycombinator.com/item?id=46212980))
- Backdated records break ID guarantees (2 comments in the sample): "one day records had to be backdated, meaning that either the IDs for those records had to be counterfeited" ([source](https://news.ycombinator.com/item?id=46277369)) "I only ever been an issue for me when I've chosen ULID as an ID for an event log" ([source](https://news.ycombinator.com/item?id=46246298))
- Easy to misuse as invariant (2 comments in the sample): "It tempts you to treat it like an invariant when it isn't." ([source](https://news.ycombinator.com/item?id=46212294)) "It's quite easy to shoot themsleves in the foot" ([source](https://news.ycombinator.com/item?id=46212989))

## The badge

A product earns the Hacker Approved badge when at least 10 people recommend it, recommenders outnumber critics at least 2 to 1 (mixed feelings count toward neither side), it was recommended in at least 4 of the 12 months and in at least 5 different threads, and no single thread supplies more than half of the people who recommend it. Health and money products are never badged.

## Cite as

Hacker Approved, "ULID", https://hackerapproved.com/p/ulid/ (11 recommend, 5 mixed, 5 criticize; Hacker News comments, November 2025 to October 2026).

Counts updated 2 Nov 2026, with data through October 31, 2026.