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RakuyoKit/JSONPreview 2.0.0
🎨 A view that previews JSON in highlighted form, it also provides the ability to format and collapse nodes.
⭐️ 44
πŸ•“ 37 weeks ago
.package(url: "https://github.com/RakuyoKit/JSONPreview.git", from: "2.0.0")



JSONPreview inherits from UIView and implements functionality based on UITextView. You can use it to format your JSON data and highlight it for display.

Also JSONPreview provides fold and expand functionality, so you can collapse nodes that you are not interested in at the moment and re-display them at any time.

All of JSONPreview's features are written using native methods, which means you get a great experience on the Apple platform.


Here is a gif of about 25 seconds (about 2.5M) that shows the effect when using this library to preview JSON.



  • iOS 10 or later.
  • Xcode 10.0 or later required.
  • Swift 5.0 or later required.



pod 'JSONPreview'

Swift Package Manager

Or add the following to your Package.swift file:

dependencies: [
  .package(url: "https://github.com/rakuyoMo/JSONPreview.git", from: "2.0.0")


In 1.3.0 version, we removed the ability to slide diagonally. Now if a JSON row is not displayed, it will be displayed folded instead of going beyond the screen. If you wish to use this feature, please use the 1.2.3 version

  • β˜‘ Support for formatted display of JSON data.

  • β˜‘ Support for highlighting JSON data, with various color and font configuration options.

  • β˜‘ Provide fold and expand for Array and Object.

  • β˜‘ Based on UITextView, meaning you can copy any content in JSONPreview.

  • JSONPreview provides limited, incomplete format checking functionality, so this feature is not provided as a main feature. For more details, please refer to: Format check


After downloading the project, ViewController.swift file contains part of the test code, just run the project Check the corresponding effect.

  1. Create the JSONPreview object and add it to the interface.
let previewView = JSONPreview()

  1. Call the preview(_:style:) method to preview the data in the default style:
let json = "{\"key\":\"value\"}"

  1. If you want to customize the highlight style, you can set it through the HighlightStyle and HighlightColor types:

Among them, ConvertibleToColor is a protocol for providing colors. Through this protocol, you can directly use the UIColor object, or easily convert such objects as 0xffffff, #FF7F20 and [0.72, 0.18, 0.13] to UIColor objects.

let highlightColor = HighlightColor(
    keyWord: ConvertibleToColor,
    key: ConvertibleToColor,
    link: ConvertibleToColor,
    string: ConvertibleToColor,
    number: ConvertibleToColor,
    boolean: ConvertibleToColor,
    null: ConvertibleToColor,
    unknownText: ConvertibleToColor,
    unknownBackground: ConvertibleToColor,
    jsonBackground: ConvertibleToColor,
    lineBackground: ConvertibleToColor,
    lineText: ConvertibleToColor

let style = HighlightStyle(
    expandIcon: UIImage?,
    foldIcon: UIImage?,
    color: highlightColor,
    lineFont: UIFont?,
    jsonFont: UIFont?,
    lineHeight: CGFloat

previewView.preview(json, style: style)

Format Check


For rendering, JSONPreview only performs limited formatting checks.

The conditions that are known to trigger Error Rendering include

  • Value Unconventional JSON types. Supported types include object, array, number, bool, string, and null.
  • Checks for the number format, such as scientific notation and decimals.
  • Spell checking for true, false and null.
  • For scientific notation, the next node of {E/e} must be +, - or a number.
  • array elements are not separated by ,.
  • object elements are not separated by ,.
  • No : after the key of object.
  • object has : after the key but is missing the value.
  • The key of object is not a string.

In addition to the conditions explicitly mentioned above, other errors may also trigger an "error rendering". There may also be errors outside the scope of the formatting check that do not trigger "error rendering". However, they may lead to missing json content.

It is recommended that you do not rely too much on JSONPreview format checking, and use it to preview correctly formatted json whenever possible.


The 1.2.0 version adds rendering of links. While rendering, JSONPreview performs a limited de-escaping operation.

The de-escaping operations supported by different versions are as follows:

If not otherwise specified, the following functions are cumulative.

  • 1.2.0: Support replacing "\\/" with "/".

Data Flow Diagram



  • ☐ Support Carthage.
  • ☐ Support for intel macOS.


Thanks to Awhisper for his valuable input during the development of JSONPreview.


JSONPreview is available under the MIT license. For more information, see LICENSE.


Stars: 44
Last commit: 11 hours ago
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Release Notes

2.0.0 - Performance Enhancement
37 weeks ago

Break Change

  • The git repository was migrated. Resulting in a url change.
  • Refers to the Swift Core Foundation framework, refactoring the entirety of parsing and rendering, with significant performance improvements.

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