SnapKit: A Swift DSL for Auto Layout on iOS and macOS

What SnapKit replaces in a UIKit or AppKit project

Plain Auto Layout means creating NSLayoutConstraint objects, activating them, and keeping references when a constraint needs to change later. SnapKit turns that into a closure. The README's Quick Start shows the shape: a view is added to its superview, then `box.snp.makeConstraints` receives a closure where `make.width.height.equalTo(50)` and `make.center.equalTo(self.view)` describe the layout. The DSL covers width, height, center and edges, and the same package targets both iOS and macOS, so an AppKit view controller can use the same style of constraint code. The intended reader is a Swift developer maintaining a UIKit or AppKit interface who finds the native constraint API noisy. It does not replace Auto Layout itself; it is a syntax layer over it.

How the snp.makeConstraints closure maps onto Auto Layout

The mechanism is a builder object. Calling `makeConstraints` on a view through the `snp` namespace starts a constraint-making session, and the `make` parameter inside the closure is that builder. Each call such as `make.width.equalTo(50)` or `make.center.equalTo(self.view)` records one relationship, and the builder turns the recorded relationships into NSLayoutConstraint instances that are installed on the view hierarchy. Because the output is ordinary Auto Layout constraints, the runtime behaviour is the same as hand-written constraints, including priority handling and the usual conflict logging when constraints cannot be satisfied. The DSL also gives you a place to hold references to constraints you will change later, which is the part of Auto Layout that is most awkward to write by hand. The repository keeps the implementation under Sources and the tests under Tests, with an Example-iOS target in the same workspace, so the DSL and its examples ship together.

Installing SnapKit with Swift Package Manager

The README documents Swift Package Manager as the integration path, and it states that Xcode 26 or later is required to build SnapKit this way. Add the package to the dependencies array of your Package.swift, pinned to the 6.x line with `.upToNextMajor(from: "6.0.0")`.

dependencies: [
    .package(url: "https://github.com/SnapKit/SnapKit.git", .upToNextMajor(from: "6.0.0"))
]

After the package resolves, `import SnapKit` in a file and call `snp.makeConstraints` on a view. A first real use is the README's example: add a green box to the view controller's view, then constrain its width and height to 50 points and center it in the parent.

import SnapKit

class MyViewController: UIViewController {

    lazy var box = UIView()

    override func viewDidLoad() {
        super.viewDidLoad()

        self.view.addSubview(box)
        box.backgroundColor = .green
        box.snp.makeConstraints { (make) -> Void in
           make.width.height.equalTo(50)
           make.center.equalTo(self.view)
        }
    }
}

With that in place the box should appear centered and 50 by 50 points. The README also says SnapKit can be integrated manually if you do not want a dependency manager, though it does not spell out the manual steps in the text shown here.

Version 6.0.0 raises the floor on Xcode and Swift

The requirements section is the constraint that decides adoption. SnapKit needs iOS 14.0 or later, macOS 12.0 or later, tvOS 14.0 or later, Xcode 26.0 or later, and a Swift 6.0 or later toolchain. The README is explicit that this is the toolchain, not the syntax, so a project can stay on older language patterns and still build. The README also warns that projects using Swift 5.x must use SnapKit 5.0.0 or later, which separates the 5.x line from the 6.x line. For teams that cannot move their build machines to Xcode 26, the practical answer is to stay on the 5.x releases, and the release list shows 5.7.1 as the last of that line. The jump from 5.7.1 to 6.0.0 is the kind of change that shows up in CI before it shows up in code: if the build image is older than the requirement, nothing compiles, regardless of how the constraint code is written.

Where SnapKit is the wrong tool

SnapKit solves constraint authoring for UIKit and AppKit. If the interface is built in SwiftUI, this package does not apply, because SwiftUI views do not expose the NSLayoutConstraint model the DSL writes into; the README does not claim SwiftUI support and the usage example is a UIViewController. The same applies to AppKit views that use layout systems other than Auto Layout. There is also a maintenance cost inside the DSL itself: constraint code written in a closure is harder to inspect at a glance than a list of activated constraints, because the relationships are implied by chained property names rather than declared one per line. When a layout breaks, the conflict log still speaks in terms of the underlying constraints, not the SnapKit calls that produced them, so debugging means mapping back from Auto Layout output to the closure that generated it. Finally, the repository is a layout library, not a UI framework: it does not provide views, styling, or a state system, and adopting it will not reduce the amount of view code outside constraints.

SnapKit compared with writing Auto Layout directly

The honest alternative is Apple's own Auto Layout API, used without a wrapper. The difference is where the verbosity lives. With NSLayoutConstraint you create each constraint, set its `isActive` flag or pass it to `NSLayoutConstraint.activate`, and store any constraint you plan to modify. With SnapKit you write the same relationships inside `makeConstraints`, and the library creates and activates the constraints for you. The trade-off is transparency against brevity. Direct constraints are explicit objects you can breakpoint and print; SnapKit calls are shorter and easier to scan once the reader knows the DSL. If your project has only a handful of constraints, the wrapper adds a dependency for little gain. If constraints are dense and change often, the closure form is the reason people reach for it. The README does not argue this case; the Quick Start simply demonstrates the shorter form.

Maintenance, licence and upgrade cost

SnapKit is MIT licensed, so the licence permits use, modification and redistribution with the copyright notice and permission notice preserved; the LICENSE file in the repository root carries the terms, and this is a summary rather than legal advice. The repository is not archived, and the last push was on 2026-07-13, which places it within the last six months of the date used here. The 6.0.0 release landed on 2026-05-31, following 5.7.1 on 2024-02-18 and 5.7.0 on 2023-12-31. That release spacing matters for planning: the gap between 5.7.1 and 6.0.0 was more than two years, so a team adopting 6.0.0 should expect to sit on that major line for a while rather than receive frequent minor updates. The upgrade cost is concentrated in the platform requirements, since the 6.x line demands Xcode 26 and a Swift 6.0 toolchain. The README links to migration guides from its contents list, so the upgrade path is documented there rather than in the README body.

Editorial conclusion

Adopt SnapKit in UIKit or AppKit codebases that already use Auto Layout and want constraint code that reads in fewer lines. Skip it for SwiftUI views, which use their own layout system, and skip it if your project cannot move to Xcode 26 and a Swift 6.0 toolchain. Before committing, verify that your deployment targets meet iOS 14.0, macOS 12.0 or tvOS 14.0, and check your constraint code against the 6.0.0 migration notes.

Frequently asked questions

Official sources

1. License: MIT
2. Project website
3. README
4. Releases
5. SnapKit/SnapKit on GitHub