SVG Optimization Techniques

SVG optimization is essential for web performance. Unoptimized SVGs often contain unnecessary metadata, redundant code, and verbose coordinates that inflate file sizes. This guide covers practical techniques to create lean, efficient SVG files.

Why Optimize SVGs?

Even though SVGs are typically smaller than raster images, they can still benefit significantly from optimization. Design software like Adobe Illustrator, Figma, and Sketch embeds metadata, uses verbose coordinate precision, and includes unnecessary attributes that browsers don't need.

Optimized SVGs load faster, reduce bandwidth usage, and can improve rendering performance. For icon libraries with hundreds of icons, these savings compound quickly.

Understanding SVG File Structure

An SVG file is XML-based markup. A typical icon SVG contains:

• Root SVG element – Defines the viewBox, dimensions, and namespace
• Metadata – Editor information, comments, and document properties
• Style definitions – CSS rules and presentation attributes
• Path elements – The actual vector shapes
• Groups – Organizational containers for related elements

For more background on SVG structure and capabilities, see the MDN SVG Tutorial.

Manual Optimization Techniques

Remove Metadata and Comments

Design tools add metadata about the application, version, and creation date. XML comments and editor-specific namespaces can be safely removed:

• Delete <!-- comments -->
• Remove xmlns:sketch, xmlns:sodipodi, and similar namespaces
• Strip <metadata> and <defs> if empty

Simplify the Coordinate System

Design tools often export coordinates with excessive decimal precision:

• Before: M12.34567890,45.67891234
• After: M12.35,45.68

For icons at typical display sizes, 1-2 decimal places are usually sufficient. Higher precision rarely produces visible differences but adds file size.

Use Relative Path Commands

Path data can use absolute (uppercase) or relative (lowercase) commands. Relative commands often produce shorter output when shapes are compact:

• Absolute: M10,10 L20,10 L20,20 L10,20 Z
• Relative: M10,10 l10,0 l0,10 l-10,0 z

Merge and Simplify Paths

Multiple separate paths can sometimes be combined into one. Compound paths reduce element count and often result in smaller files. In your design tool, use "Unite" or "Merge Paths" before export.

Automated Optimization with SVGO

SVGO (SVG Optimizer) is the industry-standard tool for automated SVG optimization. It applies a configurable set of plugins to clean and compress SVG files.

Key SVGO Plugins

• removeDoctype – Removes DOCTYPE declaration
• removeXMLProcInst – Removes XML declaration
• removeComments – Strips comments
• removeMetadata – Removes metadata elements
• removeEditorsNSData – Cleans editor namespaces
• cleanupAttrs – Removes unnecessary whitespace in attributes
• convertPathData – Optimizes path commands
• mergePaths – Combines adjacent paths when possible
• removeEmptyContainers – Deletes empty groups

Recommended SVGO Configuration

For icons, a moderately aggressive configuration works well. Be careful with plugins that remove IDs or classes if you reference them in CSS or JavaScript.

Design Tool Export Settings

Adobe Illustrator

When saving as SVG, choose "SVG Tiny" profile for icons. Disable "Preserve Illustrator Editing Capabilities" and set decimal places to 1 or 2. Use "Presentation Attributes" instead of "Style Elements" for simpler output.

Figma

Figma's SVG export is relatively clean by default. Use the "Outline Text" option for any text elements. Consider flattening complex boolean operations before export.

Sketch

Enable "SVGO Compressor" in Sketch preferences for automatic optimization on export. Flatten complex shapes and avoid excessive layer nesting.

Optimization Checklist

Follow this checklist when preparing SVG icons for production:

1. Remove all unnecessary layers and hidden elements in your design tool
2. Flatten complex boolean operations and expand strokes if needed
3. Convert text to outlines
4. Export with minimal decimal precision
5. Run through SVGO or equivalent optimizer
6. Verify the optimized file renders correctly
7. Check that any needed IDs and classes are preserved

Measuring Results

Track your optimization efforts by comparing:

• File size before and after (in bytes)
• Percentage reduction
• Visual comparison at target display sizes

For an icon library, aim for consistent optimization across all icons. Document your optimization settings so results are reproducible.