SVGift

Swift native implementation of SVGO — the popular Node.js SVG optimizer.

SVGift provides the same optimization capabilities as SVGO, with 49 built-in plugins (34 enabled by default). It is available as both a CLI tool and a Swift library.

Installation

Homebrew

brew install okooo5km/tap/svgift

Or manually:

brew tap okooo5km/tap
brew install svgift

Build from source

git clone https://github.com/okooo5km/SVGift.git
cd svgo-swift
swift build -c release
# Binary at .build/release/svgift

SwiftPM (as a library dependency)

.package(url: "https://github.com/okooo5km/SVGift.git", from: "0.3.0")

Then add "SVGift" to your target's dependencies.

Usage

CLI

# Optimize a single file (output to stdout)
svgift input.svg

# Optimize and write to a file
svgift input.svg -o output.svg

# Read from stdin
cat input.svg | svgift -

# Recursively optimize a directory (in-place)
svgift -r icons/

# Recursively optimize to a different directory
svgift -r icons/ -o optimized/

# Use a built-in preset (0-6 or name)
svgift input.svg --preset recommended
svgift input.svg --preset 4

# Enable multipass optimization
svgift input.svg --multipass -o output.svg

# Pretty-print output
svgift input.svg --pretty

# Custom indentation (default: 4, use -1 for tabs)
svgift input.svg --pretty --indent 2

# Set global float precision for numeric values
svgift input.svg --float-precision 2

# Use a config file
svgift input.svg --config svgo.config.json -o output.svg

# List available plugins / presets
svgift --show-plugins
svgift --show-presets

CLI flags (--multipass, --pretty, --indent, --float-precision) override the corresponding values in the preset or config file when provided.

Library API

import SVGift

// Basic usage with default plugins
let input = "<svg>...</svg>"
let result = try optimize(input)
print(result.data)

// Use a built-in preset
let result = try optimize(input, preset: .recommended)  // L2
let result = try optimize(input, preset: .aggressive)    // L4

// Preset with customization
var options = OptimizeOptions.preset(.compact)
options.js2svg.pretty = true  // override a single field
let result = try optimize(input, options: options)

// Fully custom options
var options = OptimizeOptions(
    plugins: presetDefaultPlugins,
    pluginRegistry: builtinPluginRegistry
)
options.multipass = true
options.js2svg.pretty = true
let result = try optimize(input, options: options)

Configuration

Create a JSON config file to customize optimization behavior:

{
  "multipass": true,
  "floatPrecision": 3,
  "js2svg": {
    "pretty": true,
    "indent": 2
  },
  "plugins": [
    "removeDoctype",
    "removeComments",
    {
      "name": "removeAttrs",
      "params": {
        "attrs": ["fill", "stroke"]
      }
    }
  ]
}

Top-level options

Field	Type	Default	Description
multipass	bool	false	Run multiple optimization passes (up to 10) until output converges
floatPrecision	int	plugin default (3)	Global float precision injected into all plugins that support it
js2svg.pretty	bool	false	Pretty-print output with indentation
js2svg.indent	int	4	Indentation width (use -1 for tabs)
js2svg.useShortTags	bool	true	Use self-closing tags (e.g. <path/>)
js2svg.finalNewline	bool	false	Add a final newline at end of file

Plugin formats

Plugins can be specified as strings, objects, or a mix of both:

{
  "plugins": [
    "removeDoctype",
    { "name": "removeComments" },
    { "name": "cleanupIds", "params": { "minify": false } },
    { "name": "removeDesc", "enabled": false }
  ]
}

When no plugins key is provided, the 34 default plugins are used.

Optimization Presets

SVGift provides 7 built-in optimization levels (L0-L6) that balance fidelity vs compression:

Level	Name	Multipass	Precision	Key Features
L0	safe	No	6	Pretty output, IDs preserved, debug-friendly
L1	conservative	Yes	4	Compact output, IDs preserved
L2	recommended	Yes	3	Balanced, removeDimensions, prefixIds
L3	compact	Yes	2	Size-oriented, ID minification
L4	aggressive	Yes	2	Strips styles/scripts/raster images
L5	extreme	Yes	1	Removes viewBox (fixed-size only)
L6	maximum	Yes	0	Removes title, needs visual verification

Use cases

• L0 safe — Debugging and development. Pretty-printed output with high precision makes it easy to inspect optimized SVGs. IDs stay intact for readability.
• L1 conservative — Production use where IDs must remain stable (e.g., CSS/JS referencing specific IDs). Multipass enabled for thorough optimization.
• L2 recommended — General production use. Adds prefixIds to prevent ID collisions when multiple SVGs are inlined on the same page, and removeDimensions so the SVG scales via CSS.
• L3 compact — Size-critical delivery (e.g., email templates, bandwidth-constrained environments). Enables ID minification for shorter output.
• L4 aggressive — Icon systems and controlled rendering environments. Strips <style>, <script>, and raster <image> elements that are unnecessary in icon pipelines.
• L5 extreme — Fixed-size rendering only (e.g., <img> tags with explicit width/height, or native renderers). Removes viewBox, so the SVG cannot scale responsively.
• L6 maximum — Maximum compression with visual verification required. Also removes <title> (impacts accessibility). Use only when every byte counts and you can manually verify the output.

Incremental differences

Each level builds on the previous one. Here is what changes at each step:

Transition	Changes
L0 → L1	Enable multipass; reduce precision 6→4; disable pretty output
L1 → L2	Reduce precision 4→3; enable removeDesc, removeDimensions, prefixIds
L2 → L3	Reduce precision 3→2; enable cleanupIds minification; remove prefixIds
L3 → L4	Add removeStyleElement, removeScripts, removeRasterImages
L4 → L5	Reduce precision 2→1; add removeViewBox
L5 → L6	Reduce precision 1→0; add removeTitle

Combining presets with CLI flags

CLI flags override the corresponding preset values, so you can fine-tune without writing a config file:

# Use recommended preset but keep pretty output for review
svgift input.svg --preset recommended --pretty

# Use compact preset with custom precision
svgift input.svg --preset compact --float-precision 3

# Use aggressive preset without multipass (single-pass only)
svgift input.svg --preset aggressive --no-multipass

# Recursively optimize a directory with a preset
svgift -r icons/ --preset aggressive -o optimized/

In the library API, modify the returned options object:

var options = OptimizeOptions.preset(.compact)
options.js2svg.pretty = true           // override output format
options.js2svg.indent = 2              // custom indent width
options.floatPrecision = 4             // override precision
let result = try optimize(svg, options: options)

Risk warnings

L5/L6: removeViewBox — Without viewBox, the SVG cannot scale responsively. Only use when the SVG is rendered at a fixed size (e.g., <img width="24" height="24">). If you later need the SVG to be responsive, you will need to re-optimize from the original source.

L6: removeTitle — The <title> element provides an accessible name for screen readers. Removing it degrades accessibility. Ensure alternative accessible labels are provided in the surrounding HTML (e.g., aria-label on the container).

L4+: removeStyleElement / removeScripts — These levels strip all <style> and <script> content. SVGs that rely on CSS animations, hover effects, or JavaScript interactivity will break. Verify the SVG does not depend on these features before using L4+.

Plugins

49 built-in plugins are available. See docs/plugins.md for the complete list with descriptions and parameters.

Default plugins (34): removeDoctype, removeXMLProcInst, removeComments, removeDeprecatedAttrs, removeMetadata, removeEditorsNSData, cleanupAttrs, mergeStyles, inlineStyles, minifyStyles, cleanupIds, removeUselessDefs, cleanupNumericValues, convertColors, removeUnknownsAndDefaults, removeNonInheritableGroupAttrs, removeUselessStrokeAndFill, cleanupEnableBackground, removeHiddenElems, removeEmptyText, convertShapeToPath, convertEllipseToCircle, moveElemsAttrsToGroup, moveGroupAttrsToElems, collapseGroups, convertPathData, convertTransform, removeEmptyAttrs, removeEmptyContainers, mergePaths, removeUnusedNS, sortAttrs, sortDefsChildren, removeDesc

Compatibility

SVGift aims for full compatibility with SVGO's optimization output. The test suite validates against 363 SVGO test fixtures with 100% pass rate (L1 byte-exact and L2 normalized matching).

Contributing

1. Fork the repository
2. Create your feature branch (git checkout -b feature/amazing-feature)
3. Run tests (swift test)
4. Commit your changes
5. Push to the branch and open a Pull Request

License

MIT License. See LICENSE for details.

Credits

• SVGO — the original Node.js SVG optimizer
• Built by okooo5km (十里)