Slug
A schema type for slugs is typically used to create unique URLs.
A slug is a unique string (typically a normalized version of title or other representative string), often used as part of a URL. The input form will render an error message if the current slug field is not unique (see note on uniqueness below).
Properties
Requiredtype
Value must be set to
slug.
Requiredname
Required. The field name. This will be the key in the data record.
title
Human readable label for the field.
If set to
true, this field will be hidden in the studio. You can also return a callback function to use it as a conditional field.
readOnly
If set to
true, this field will not be editable in the content studio. You can also return a callback function to use it as a conditional field.
description
Short description to editors how the field is to be used.
initialValue
The initial value used when creating new values from this type. Can be either a literal value or a resolver function that returns either a literal value or a promise resolving to the initial value.
deprecated
Marks a field or document type as deprecated in the studio interface and displays a user-defined message defined by the single required
reasonproperty.If you deploy a GraphQL API schema, this property will translated into the
@deprecateddirective.
Options
source
The name of the field which the slug value is derived from. If a string is provided, it should match the name of the source field in your schema. If a function is provided, the source function is called with two parameters:
doc(object - the current document) andoptions(object - withparentandparentPathkeys for easy access to sibling fields).
maxLength
Maximum number of characters the slug may contain when generating it from a source (like a title field) with the default slugify function. Defaults to
200. If you include your own slugify function, or manually enter your slug this option will be ignored.
slugify
Supply a custom override function which handles string normalization.
slugifyis called with three parameters:input(string),type(object - schema type) andcontext(object). Ifslugifyis set, themaxLengthoption is ignored.
isUnique
Supply a custom function which checks whether or not the slug is unique. Receives the proposed slug as the first argument and an options object.
Validation
required()
Ensures that this field exists.
custom(fn)
Creates a custom validation rule.
By default, the slug input will check for uniqueness based on the document type and the path to the slug field. For instance, a document of type article and a document of type product can have the same slug. You can customize this behavior by defining an isUnique function in the field options.
The value of the slug field is stored on the current property.
Input
{
title: 'Slug',
name: 'slug',
type: 'slug',
options: {
source: 'title',
maxLength: 200, // will be ignored if slugify is set
slugify: input => input
.toLowerCase()
.replace(/\s+/g, '-')
.slice(0, 200)
}
}Response
{
"_type": "slug",
"current": "this-is-the-title"
}Custom slugify function
import slugify from 'some-off-the-shelf-slugifier'
async function myAsyncSlugifier(input, schemaType, context) {
const slug = slugify(input)
const {getClient} = context
const client = getClient({apiVersion: '2022-12-07'})
const query = 'count(*[_type=="movie" && slug.current == $slug]{_id})'
const params = {slug: slug}
return client.fetch(query, params).then((count) => {
console.log('Movies with identical slug', count)
return `${slug}-${count + 1}`
})
return slug
}
//…
// schema field
{
title: 'Slug',
name: 'slug',
type: 'slug',
options: {
source: 'title',
slugify: myAsyncSlugifier
}
}Custom isUnique function
By default the isUnique function checks for uniqueness across all documents of the same type. Here's an example of an isUnique function that checks for uniqueness across all documents in your dataset:
import { getPublishedId } from 'sanity';
export async function isUniqueAcrossAllDocuments(
slug,
context
) {
const { document, getClient } = context;
const client = getClient({ apiVersion: '2025-02-19' });
const id = document?._id;
if (!id || !slug?.current) {
return true;
}
const publishedId = getPublishedId(id);
const params = {
published: publishedId,
slug: slug.current,
};
const query = groq`!defined(*[
!sanity::versionOf($published) &&
slug.current == $slug
][0]._id)`;
const isUnique = await client.fetch(query, params);
return isUnique || false;
}import {isUniqueAcrossAllDocuments} from '../lib/isUniqueAcrossAllDocuments'
export default {
name: 'post',
type: 'document',
title: 'Post',
fields: [
{
name: 'title',
type: 'string',
title: 'Title'
},
{
name: 'slug',
type: 'slug',
title: 'Slug',
options: {
isUnique: isUniqueAcrossAllDocuments
}
}
]
}Keep in mind that unlike other validator functions that can pass a message, isUnique expects a boolean response.
Custom source function
It's also possible to provide the source as a function, that will be called with a first argument containing the whole document, and a second containing a context object.
{
title: 'Slug',
name: 'slug',
type: 'slug',
options: {
// include category if dataset is production
source: (doc, context) => context.dataset === 'production' ? `${doc.category}-${doc.title}` : doc.title
}
}The source function also receives an options object containing the parent object/array, if any. It can be useful if you want to derive the slug from a sibling field instead of a property on the document root:
{
title: 'Slug',
name: 'slug',
type: 'slug',
options: {
source: (doc, context) => context.parent.title
}
}To query for a document with a given slug, make sure you put the constraint on the current key:
*[_type == "your-document-type" && slugFieldName.current == "your-slug"]
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