Custom extensions

Most editor features in ProseKit are themselves extensions. When the official ones don’t fit, you write your own and union them in.

When you actually need a custom extension

Goal	Reach for
Bind a key	`defineKeymap`
Run a command	`defineCommands`
Listen to events	`defineKeyDownHandler`, `definePasteHandler`, …
Add a node or mark	`defineNodeSpec`, `defineMarkSpec`
Add an attribute to an existing node	`defineNodeAttr`
Drop in a raw ProseMirror plugin	`definePlugin`
Render a node with a framework component	Custom node views

Most of those are one-call extensions. You only need a “full” custom extension when you’re combining several of them.

Anatomy of a typical extension

The official extensions follow a consistent shape. Here’s what defineBold looks like, simplified:

import { defineCommandsfunction defineCommands<T extends Record<string, CommandCreator> = Record<string, CommandCreator>>(commands: T): Extension<{
    Commands: { [K in keyof T]: Parameters<T[K]>; };
}>, defineKeymapfunction defineKeymap(keymap: Keymap): PlainExtensionAdds a set of keybindings to the editor. Please read the
[documentation](https://prosemirror.net/docs/ref/#keymap) for more details., defineMarkSpecfunction defineMarkSpec<Mark extends string, Attrs extends AnyAttrs = Attrs>(options: MarkSpecOptions<Mark, Attrs>): Extension<{
    Marks: { [K in Mark]: Attrs; };
}>Defines a mark type into the editor schema.
@example```ts
const extension = defineMarkSpec({
  name: 'bold',
  parseDOM: [
    { tag: 'strong' },
    { tag: 'b' },
  ],
  toDOM() {
    return ['strong', 0]
  },
})
```, unionfunction union<const E extends readonly Extension[]>(...exts: E): Union<E> (+1 overload)Merges multiple extensions into one. You can pass multiple extensions as
arguments or a single array containing multiple extensions.
@throwsIf no extensions are provided.@example```ts
function defineFancyNodes() {
  return union(
    defineFancyParagraph(),
    defineFancyHeading(),
  )
}
```@example```ts
function defineFancyNodes() {
  return union([
    defineFancyParagraph(),
    defineFancyHeading(),
  ])
}
```, type Extensioninterface Extension<T extends ExtensionTyping<any, any, any> = ExtensionTyping<any, any, any>>, type Uniontype Union<E extends readonly Extension[]> = Extension<{
    Nodes: ExtractNodes<E[number]>;
    Marks: ExtractMarks<E[number]>;
    Commands: ExtractCommands<E[number]>;
}>@internal } from 'prosekit/core'
import { toggleMarkfunction toggleMark({ type, attrs, removeWhenPresent, enterInlineAtoms, }: ToggleMarkOptions): CommandReturns a command that toggles the given mark with the given attributes.
@paramoptions } from 'prosekit/core'

const myBoldSpecconst myBoldSpec: Extension<ExtensionTyping<any, any, any>>: Extensioninterface Extension<T extends ExtensionTyping<any, any, any> = ExtensionTyping<any, any, any>> = defineMarkSpecdefineMarkSpec<"bold", Attrs>(options: MarkSpecOptions<"bold", Attrs>): Extension<{
    Marks: {
        bold: Attrs;
    };
}>Defines a mark type into the editor schema.
@example```ts
const extension = defineMarkSpec({
  name: 'bold',
  parseDOM: [
    { tag: 'strong' },
    { tag: 'b' },
  ],
  toDOM() {
    return ['strong', 0]
  },
})
```({
  nameMarkSpecOptions<"bold", Attrs>.name: "bold"The name of the mark type.: 'bold',
  parseDOMMarkSpec.parseDOM?: readonly ParseRule[] | undefinedAssociates DOM parser information with this mark (see the
corresponding [node spec field](https://prosemirror.net/docs/ref/#model.NodeSpec.parseDOM)). The
`mark` field in the rules is implied.: [{ tagTagParseRule.tag: stringA CSS selector describing the kind of DOM elements to match.: 'strong' }, { tagTagParseRule.tag: stringA CSS selector describing the kind of DOM elements to match.: 'b' }],
  toDOMMarkSpec.toDOM?: ((mark: Mark, inline: boolean) => DOMOutputSpec) | undefinedDefines the default way marks of this type should be serialized
to DOM/HTML. When the resulting spec contains a hole, that is
where the marked content is placed. Otherwise, it is appended to
the top node.: () => ['strong', 0],
})

const myBoldCommandsconst myBoldCommands: Extension<{
    Commands: {
        toggleBold: [];
    };
}> = defineCommandsdefineCommands<{
    toggleBold: () => Command;
}>(commands: {
    toggleBold: () => Command;
}): Extension<{
    Commands: {
        toggleBold: [];
    };
}>({
  toggleBoldtoggleBold: () => Command: () => toggleMarkfunction toggleMark({ type, attrs, removeWhenPresent, enterInlineAtoms, }: ToggleMarkOptions): CommandReturns a command that toggles the given mark with the given attributes.
@paramoptions({ typeToggleMarkOptions.type: string | MarkTypeThe mark type to toggle.: 'bold' }),
})

const myBoldKeymapconst myBoldKeymap: PlainExtension = defineKeymapfunction defineKeymap(keymap: Keymap): PlainExtensionAdds a set of keybindings to the editor. Please read the
[documentation](https://prosemirror.net/docs/ref/#keymap) for more details.({
  'Mod-b': toggleMarkfunction toggleMark({ type, attrs, removeWhenPresent, enterInlineAtoms, }: ToggleMarkOptions): CommandReturns a command that toggles the given mark with the given attributes.
@paramoptions({ typeToggleMarkOptions.type: string | MarkTypeThe mark type to toggle.: 'bold' }),
})

export function defineMyBoldfunction defineMyBold(): Union<readonly [Extension<ExtensionTyping<any, any, any>>, Extension<{
    Commands: {
        toggleBold: [];
    };
}>, PlainExtension]>() {
  return unionunion<readonly [Extension<ExtensionTyping<any, any, any>>, Extension<{
    Commands: {
        toggleBold: [];
    };
}>, PlainExtension]>(exts_0: Extension<ExtensionTyping<any, any, any>>, exts_1: Extension<{
    Commands: {
        toggleBold: [];
    };
}>, exts_2: PlainExtension): Union<readonly [Extension<ExtensionTyping<any, any, any>>, Extension<{
    Commands: {
        toggleBold: [];
    };
}>, PlainExtension]> (+1 overload)Merges multiple extensions into one. You can pass multiple extensions as
arguments or a single array containing multiple extensions.
@throwsIf no extensions are provided.@example```ts
function defineFancyNodes() {
  return union(
    defineFancyParagraph(),
    defineFancyHeading(),
  )
}
```@example```ts
function defineFancyNodes() {
  return union([
    defineFancyParagraph(),
    defineFancyHeading(),
  ])
}
```(
    myBoldSpecconst myBoldSpec: Extension<ExtensionTyping<any, any, any>>,
    myBoldCommandsconst myBoldCommands: Extension<{
    Commands: {
        toggleBold: [];
    };
}>,
    myBoldKeymapconst myBoldKeymap: PlainExtension,
  )
}

Three building blocks (spec, commands, keymap) joined by union. Same pattern works for any feature: define each piece in isolation, then compose. See Concepts → Extensions for the full story.

Adding to an existing editor

import { defineBasicExtensionfunction defineBasicExtension(): BasicExtensionDefine a basic extension that includes some common functionality. You can
copy this function and customize it to your needs.

It's a combination of the following extension functions:

- 
{@link 
defineDoc
}

- 
{@link 
defineText
}

- 
{@link 
defineParagraph
}

- 
{@link 
defineHeading
}

- 
{@link 
defineList
}

- 
{@link 
defineBlockquote
}

- 
{@link 
defineImage
}

- 
{@link 
defineHorizontalRule
}

- 
{@link 
defineHardBreak
}

- 
{@link 
defineTable
}

- 
{@link 
defineCodeBlock
}

- 
{@link 
defineItalic
}

- 
{@link 
defineBold
}

- 
{@link 
defineUnderline
}

- 
{@link 
defineStrike
}

- 
{@link 
defineCode
}

- 
{@link 
defineLink
}

- 
{@link 
defineBaseKeymap
}

- 
{@link 
defineBaseCommands
}

- 
{@link 
defineHistory
}

- 
{@link 
defineGapCursor
}

- 
{@link 
defineVirtualSelection
}

- 
{@link 
defineModClickPrevention
} } from 'prosekit/basic'
import { createEditorfunction createEditor<E extends Extension>(options: EditorOptions<E>): Editor<E>, defineKeymapfunction defineKeymap(keymap: Keymap): PlainExtensionAdds a set of keybindings to the editor. Please read the
[documentation](https://prosemirror.net/docs/ref/#keymap) for more details., unionfunction union<const E extends readonly Extension[]>(...exts: E): Union<E> (+1 overload)Merges multiple extensions into one. You can pass multiple extensions as
arguments or a single array containing multiple extensions.
@throwsIf no extensions are provided.@example```ts
function defineFancyNodes() {
  return union(
    defineFancyParagraph(),
    defineFancyHeading(),
  )
}
```@example```ts
function defineFancyNodes() {
  return union([
    defineFancyParagraph(),
    defineFancyHeading(),
  ])
}
``` } from 'prosekit/core'

const myKeymapconst myKeymap: PlainExtension = defineKeymapfunction defineKeymap(keymap: Keymap): PlainExtensionAdds a set of keybindings to the editor. Please read the
[documentation](https://prosemirror.net/docs/ref/#keymap) for more details.({
  'Mod-Shift-x': () => {
    consolevar console: Console.logConsole.log(...data: any[]): voidThe **`console.log()`** static method outputs a message to the console.

[MDN Reference](https://developer.mozilla.org/docs/Web/API/console/log_static)('custom shortcut')
    return true
  },
})

const editorconst editor: Editor<Union<readonly [BasicExtension, PlainExtension]>> = createEditorcreateEditor<Union<readonly [BasicExtension, PlainExtension]>>(options: EditorOptions<Union<readonly [BasicExtension, PlainExtension]>>): Editor<Union<readonly [BasicExtension, PlainExtension]>>({
  extensionEditorOptions<Union<readonly [BasicExtension, PlainExtension]>>.extension: Union<readonly [BasicExtension, PlainExtension]>The extension to use when creating the editor.: unionunion<readonly [BasicExtension, PlainExtension]>(exts_0: BasicExtension, exts_1: PlainExtension): Union<readonly [BasicExtension, PlainExtension]> (+1 overload)Merges multiple extensions into one. You can pass multiple extensions as
arguments or a single array containing multiple extensions.
@throwsIf no extensions are provided.@example```ts
function defineFancyNodes() {
  return union(
    defineFancyParagraph(),
    defineFancyHeading(),
  )
}
```@example```ts
function defineFancyNodes() {
  return union([
    defineFancyParagraph(),
    defineFancyHeading(),
  ])
}
```(defineBasicExtensionfunction defineBasicExtension(): BasicExtensionDefine a basic extension that includes some common functionality. You can
copy this function and customize it to your needs.

It's a combination of the following extension functions:

- 
{@link 
defineDoc
}

- 
{@link 
defineText
}

- 
{@link 
defineParagraph
}

- 
{@link 
defineHeading
}

- 
{@link 
defineList
}

- 
{@link 
defineBlockquote
}

- 
{@link 
defineImage
}

- 
{@link 
defineHorizontalRule
}

- 
{@link 
defineHardBreak
}

- 
{@link 
defineTable
}

- 
{@link 
defineCodeBlock
}

- 
{@link 
defineItalic
}

- 
{@link 
defineBold
}

- 
{@link 
defineUnderline
}

- 
{@link 
defineStrike
}

- 
{@link 
defineCode
}

- 
{@link 
defineLink
}

- 
{@link 
defineBaseKeymap
}

- 
{@link 
defineBaseCommands
}

- 
{@link 
defineHistory
}

- 
{@link 
defineGapCursor
}

- 
{@link 
defineVirtualSelection
}

- 
{@link 
defineModClickPrevention
}(), myKeymapconst myKeymap: PlainExtension),
})

Or, after the editor exists, hot-add it with editor.use(extension) (see Concepts → The Editor).

Publishing as a package

Ready to share your extension on npm? The prosekit-extension-template repository is a complete, working example. It packages a small YouTube-embed extension and wires up everything you need to ship it and release new versions: a TypeScript build, browser-based tests, and an automated pipeline that publishes to npm from Conventional Commits via release-please and npm trusted publishing (OIDC).

Clone it, rename the package in package.json, and follow its README to cut your first release.