> ## Documentation Index
> Fetch the complete documentation index at: https://help.qrtub.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Item ID

> The identifier you control on each Item: unique within its Collection, optional, and the value ID-based Links are built from

Item ID is your own identifier for an Item — the plant number, asset number, or tag number your
business already uses. Unlike Name, it is unique within the Collection, which makes it the field
you use to tell two similar Items apart.

## Uniqueness and blank values

No two Items in the same Collection can hold the same Item ID. The constraint is per Collection,
so "EXC-203" in Heavy Equipment and "EXC-203" in Hire Fleet are fine — the same value twice in
one Collection is rejected.

Item ID is optional. Values are trimmed before they are stored, and a blank or whitespace-only
value is stored as no value at all, so any number of Items in a Collection can have no Item ID
without colliding with each other. Trimming also means `" EXC-203 "` and `"EXC-203"` are the
same Item ID, not two different ones.

## Where Item ID appears

* In the items table, and as the subtitle under an Item's name when another Item references it
  through a reference field.
* In the search box of the item picker inside the item form, alongside Name and Description.
* In bindings, as `{{item.item_id}}` — usable in a Destination URL such as
  `https://example.com/items/{{item.item_id}}`. Bindings are inserted exactly as stored with no
  URL encoding, so keep Item IDs free of spaces and `&` if you build URLs from them.

## Item ID and ID-based Links

If the Collection generates Links from Item IDs, the Item ID *is* the Link's slug. The
Collection defines a mask — a prefix, a digit count, and an optional suffix, such as
`CRA####TL` — and an Item with the Item ID `CRA0042TL` gets the Link `qrtub.com/CRA0042TL`.

That mode adds real rules to this field:

* The Item ID must match the mask. The check runs in the item form, in the API, and on CSV
  import, and a value like `CRA42TL` is rejected for having the wrong number of digits.
* An Item saved with no Item ID is created successfully but gets no Link, because there is
  nothing to build the slug from. You will see a message saying so.
* If that slug already exists as an unassigned Link — a code you pre-printed — the existing Link
  is adopted rather than duplicated. If it is already attached to a different Item, the save is
  rejected and you are told to pick an unused number.

None of this applies in the other link-generation modes, where Item ID is simply an identifier
you keep for your own reference.

## Two behaviors that surprise people

**Duplicating an Item never copies its Item ID**, because the copy would collide on the
uniqueness constraint. You are prompted for a new one instead.

**On CSV import, duplicate Item IDs are caught in the preview**, before anything is written —
both a value already used by another Item in the Collection and the same value appearing twice
in the file. Those rows are rejected individually; the rest of the file still imports.

## Related

* [What Is an Item?](/items/overview)
* [Name and Description](/items/name-and-description)
* [Duplicating an Item](/items/duplicating)
* [Importing Items from CSV](/import-export/importing-items)