---
title: "Read between the strokes with PencilKit"
description: "Use PencilKit in iOS 27 and related platforms to recognize handwriting, index and search drawings, convert paths, track strokes, and slice strokes."
shoutout: "Unofficial, made with love by Superwall - the best way to monetize your apps."
category: "App Services"
---

# Read between the strokes with PencilKit


[Watch on Apple Developer](https://developer.apple.com/videos/play/wwdc2026/203/)

Use PencilKit in iOS 27 and related platforms to recognize handwriting, index and search drawings, convert paths, track strokes, and slice strokes.

## TL;DR

- PKStrokeRecognizer brings on-device handwriting recognition to PencilKit on iOS, iPadOS, macOS, and visionOS 27, with recognized text, indexable content, and search results.
- Recognition can use device languages or explicit preferredLanguages, supports subsets of strokes by stroke ID, and exposes supportedLanguages and recognizerVersion for language handling and re-indexing.
- PKStrokePath can convert to and from Bézier paths, making handwriting recognition usable with custom canvases that do not use PKCanvasView.
- New model APIs add stable stroke identity, selection change access, controllable wet-ink render groups, programmatic erasing, and parametric substroke extraction.

## Handwriting recognition with PKStrokeRecognizer

PKStrokeRecognizer is a Swift actor, so recognition work is asynchronous and thread-safe by design. It can recognize an entire PKDrawing or a subset of strokes identified by stroke IDs.

By default, the recognizer uses the device's languages to interpret handwriting. Apps can set preferredLanguages when the app has stronger context, such as a flashcard or language-learning workflow. The supportedLanguages property exposes the available recognition languages; the session notes 29 supported languages as of iOS 27. In Simulator, handwriting recognition is limited to languages that use Latin characters.

Recognition runs entirely on device using an offline model included with the operating system, and is available on iOS, iPadOS, macOS, and visionOS 27.

- Use recognizedText() when the app needs the single most likely transcription.
- Use updateDrawing(_:) before requesting recognition results.
- Use stroke IDs to scope recognition to part of a drawing when needed.
- Consider preferredLanguages for multilingual or language-specific app contexts.

### Recognize the most likely text

Updates the recognizer with a drawing and displays the best recognized text result.

```swift
import PencilKit

let recognizer = PKStrokeRecognizer()
await recognizer.updateDrawing(drawing)
myLabel.text = await recognizer.recognizedText()
```

## Indexing, search, and accessibility

Indexable content returns a single string representing the contents of the full drawing. Unlike recognized text, it can include multiple candidate interpretations, which is useful when handwriting is ambiguous or when multiple languages are active.

For persisted indexes, store recognizerVersion alongside indexedContent. When loading previously indexed content, compare the stored version with the current recognizer version and re-index when the recognition model has changed. Avoid calling recognition on every stroke unless the feature needs that immediacy; throttling can reduce power use.

The search API takes a target string and returns results with bounds for likely matches in the drawing. Those bounds can drive highlights, navigation, and assistive features. The session specifically calls out pairing search() with UIFindInteraction and UIFindInteractionDelegate to provide the system find UI over a drawing canvas.

- Use indexableContent for Spotlight-style indexing.
- Use search(_:) for interactive handwritten text search and match highlighting.
- Connect recognition results to VoiceOver so handwritten content can be spoken aloud.
- Use search result locations to help assistive features navigate to words in a drawing.

### Create indexable handwriting content

Gets a searchable text representation of the full drawing for app indexing.

```swift
import PencilKit

let recognizer = PKStrokeRecognizer()
await recognizer.updateDrawing(drawing)
if let indexedContent = await recognizer.indexableContent {
    index(text: indexedContent)
}
```

### Find and highlight handwritten text

Searches handwritten content and uses result bounds to highlight matches.

```swift
import PencilKit

let recognizer = PKStrokeRecognizer()
await recognizer.updateDrawing(drawing)
let results = await recognizer.search("apple")
for result in results {
    highlight(bounds: result.bounds)
}
```

## Path conversion for custom canvases

PencilKit stores stroke paths as cubic uniform B-splines, while many custom drawing systems store strokes as Bézier paths. In iOS 27, PKStrokePath supports conversion between PencilKit stroke paths and Bézier paths.

PencilKit handles the geometry during conversion, but Bézier paths do not carry PencilKit-specific values such as size, opacity, or force. Apps converting from Bézier data must provide those properties for the resulting control points.

Converting from PKStrokePath to a Bézier path and back preserves control point locations, enabling apps to store PencilKit strokes in a Bézier-based format and reconstruct them without losing path fidelity. Apps with their own canvas can convert existing Bézier strokes into PKStrokePaths, build a PKDrawing, and pass it to PKStrokeRecognizer without adopting PKCanvasView.

- Use path conversion to bring handwriting recognition to non-PKCanvasView canvases.
- Preserve or synthesize PencilKit stroke properties when importing Bézier paths.
- Refer to the WWDC20 PencilKit drawing model session for background on PKStrokePath storage.

## Deeper drawing model access

iOS 27 adds model-level access that supports more customized drawing experiences. PKStroke and PKStrokePath conform to Identifiable, with a stable UUID that survives transforms, edits, and undo operations.

With stable stroke identity, apps can track individual strokes over time and control selection state on PKCanvasView. A new canvasViewSelectionDidChange delegate callback lets apps respond when the user changes the canvas selection.

PencilKit also exposes control over wet-ink render grouping. When certain inks are drawn together quickly, PencilKit can composite strokes as if the ink is still wet by using the same renderGroupID; in iOS 27 that grouping is controllable.

- Track strokes across edits using stable Identifiable IDs.
- Control PKCanvasView selection state programmatically.
- Observe user selection changes with canvasViewSelectionDidChange.
- Adjust renderGroupID behavior for wet-ink compositing use cases.

## Stroke slicing, erasing, and substrokes

The new slicing APIs cover two related workflows: programmatic erasing and substroke extraction. PencilKit already represents partial erasure with stroke masks; iOS 27 lets apps apply that operation programmatically by providing a PKStrokePath as the eraser.

Programmatic erasing cuts through the drawing and can split a single stroke into multiple independent strokes with their own masks, matching what would happen if the user erased on the canvas. This can be expensive for complex drawings, so apps with many strokes should consider doing erasing work off the main UI path.

Substroke extraction lets apps obtain a section of a PKStroke or PKStrokePath using parametric ranges along the path. PencilKit maintains consistency for ink features such as pencil texture particles that are positioned relative to the full stroke. The session demonstrates using substrokes to replay handwriting order for Chinese character practice, with PencilKit rendering implemented in Metal for smooth animation.

- Use programmatic erasing to cut strokes using an eraser path.
- Use parametric range subscripting on PKStroke or PKStrokePath to extract precise substrokes.
- Consider performance carefully when slicing drawings with many strokes.
- Use substrokes for animations, editing tools, and stroke-order visualizations.

## Resources

- [Controlling stroke rendering for animation and editing](https://developer.apple.com/documentation/PencilKit/controlling-stroke-rendering-for-animation-and-editing)
- [Recognizing handwriting and converting it to text](https://developer.apple.com/documentation/PencilKit/recognizing-handwriting-and-converting-to-text)
- [Building a handwriting recognition experience with PencilKit](https://developer.apple.com/documentation/PencilKit/building-a-handwriting-recognition-experience-with-pencilkit)
- [PencilKit](https://developer.apple.com/documentation/PencilKit)

## Related Sessions

- [Unwrap PaperKit](https://wwdc.ai/2026/372)
- [Meet PaperKit](https://developer.apple.com/videos/play/wwdc2025/285)
- [Inspect, modify, and construct PencilKit drawings](https://developer.apple.com/videos/play/wwdc2020/10148)

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