Fields
What a field can and cannot enforce: links, uniqueness, selects, formulas, types and validation.
A field stores a value. It does not enforce a rule. Every rule below is a fact of the platform.
Links
A linked record field points at exactly one table. There is no polymorphic link, a link that targets a person or an organization depending on the row.
A linked record field can prefer one record. The setting is not enforced. It only restricts the record picker. A duplicate, a paste or the inverse side can still store two links. Turning the setting off does not alter existing links.
Creating a link field always creates its inverse in the other table. The inverse takes the name of the table.
Uniqueness
Nothing enforces uniqueness. There is no unique constraint and no composite key. Autonumber is the only field type that generates unique values. The dedupe tool finds duplicates after the fact. Airtable says it “won’t prevent duplicates”.
Selects
Select options belong to one field. No enumeration is shared across tables or bases. The API does not set a default option.
A linked record or a select cannot be the primary field. The primary field has no default value.
Structure
There is no table inheritance and no subtype.
A field has no validity period. A field has no history beyond the revision retention.
Formulas
A formula reads only its own row. A value from another table arrives by lookup through a link. Formula, lookup and rollup fields are read only.
Types
There is no JSON field type.
Currency is a number with the symbol set on the field. One column holds one currency.
Duration is a number of seconds.
Long text holds 100,000 characters.
Validation
A field has no validation in the grid, in the API or in automations. Rules for required, length, range and format exist only in forms and record detail pages.
API
A field created through the API cannot be deleted through the API.
The revision history of a record lists users, automations, syncs and API calls as authors. The API cannot read it.
Sources
- Linking records in Airtable: one table per link; the single-record preference and what it does not enforce. Verified 2026-11-05.
- Supported field types: the full list of types; no JSON; autonumber as the only unique generator. Verified 2026-09-14.
- Dedupe extension: “won’t prevent duplicates”. Verified 2026-09-14.
- Long text fields: 100,000 characters. Verified 2026-09-14.
- Getting started with Airtable sync: formulas and lookups sync as their result type. Verified 2026-11-05.