Optical Kerning vs Metric Kerning: A Complete Guide for Designers
If you have ever opened InDesign, Illustrator, or Figma and wondered whether to choose optical kerning or metric kerning, you are not alone. This is one of the most common typographic decisions designers face, and the wrong choice can make beautifully crafted layouts look subtly off.
In this guide, we break down exactly how optical kerning and metric kerning work, when each option produces better results, and how to decide which one to use for headlines, body text, and logo projects.
What Is Kerning, and Why Does It Matter?
Kerning is the adjustment of space between individual letter pairs. Unlike tracking, which adjusts spacing uniformly across a range of characters, kerning targets specific pairs like AV, To, or WA where the default spacing can look uneven to the human eye.
Good kerning makes text feel balanced and readable. Poor kerning creates awkward gaps or collisions that distract readers, even if they cannot consciously identify the problem.
Most professional design applications give you two automatic kerning methods to choose from: metric and optical. Understanding the difference between them is essential for any serious design work.
What Is Metric Kerning?
Metric kerning (sometimes called “metrics” in software menus) uses the kerning tables built into the font file by the typeface designer. When a font is created, the designer carefully defines spacing values for hundreds or even thousands of specific letter pairs. These values are stored inside the font as metadata.
When you select metric kerning in your design software, the application reads those built-in pair values and applies them automatically.
Strengths of Metric Kerning
- Reflects the original intent of the type designer, who spent considerable time fine-tuning letter pair relationships.
- Produces highly consistent results across long blocks of text.
- Works exceptionally well with professional, well-crafted fonts that include extensive kerning tables.
- Generally the default setting in most design applications for good reason.
Weaknesses of Metric Kerning
- Only as good as the kerning data in the font. Budget or free fonts often have incomplete or missing kerning tables.
- Cannot adapt when you mix different typefaces in the same line of text.
- May produce looser spacing than desired at large display sizes.
What Is Optical Kerning?
Optical kerning ignores the font’s built-in kerning tables entirely. Instead, the design software analyzes the actual shapes of adjacent characters and calculates spacing on the fly based on their outlines. The algorithm tries to create visually even spacing by looking at the geometry of each letter pair.
Strengths of Optical Kerning
- Works well with fonts that have poor or missing kerning tables.
- Produces good results when mixing two or more different typefaces on the same line.
- Can deliver tighter, more visually balanced spacing at large display sizes.
- Useful as a starting point before manual kerning adjustments.
Weaknesses of Optical Kerning
- Ignores the carefully crafted decisions of the original type designer.
- May produce inconsistent results in long passages of body text.
- The algorithm is not perfect and can sometimes over-correct or under-correct specific pairs.
- Can slow down performance in very long documents because spacing is calculated in real time.
Optical Kerning vs Metric Kerning: Side-by-Side Comparison
| Feature | Metric Kerning | Optical Kerning |
|---|---|---|
| Data source | Built-in font kerning tables | Algorithm analyzes character shapes |
| Best for body text | Yes (with quality fonts) | Only if font has poor kerning data |
| Best for headlines | Sometimes too loose | Often tighter and more balanced |
| Mixed typefaces | Poor (tables don’t cover cross-font pairs) | Good (shape-based calculation adapts) |
| Logo and display work | Starting point, then manual adjustments | Better starting point for manual refinement |
| Free/budget fonts | Often produces poor results | Usually better than metrics in this case |
| Performance | Fast (reads stored values) | Slightly slower (real-time calculation) |
When to Use Metric Kerning
Metric kerning should be your default choice for body text when you are working with professional, well-made typefaces. Foundries like Adobe, Monotype, and independent type designers invest significant effort into their kerning tables, and using metrics honors that work.
Ideal scenarios for metric kerning:
- Long-form body text in books, magazines, reports, and websites where consistency across thousands of words is critical.
- Professional fonts from reputable foundries that you know include thorough kerning data.
- Tabular data and numbers where consistent spacing ensures columns align properly.
- Templates and brand guidelines where reproducibility matters across different team members and machines.
When to Use Optical Kerning
Optical kerning shines in situations where the built-in font data either does not exist, is incomplete, or simply does not apply.
Ideal scenarios for optical kerning:
- Headlines and display text set at large sizes where even minor spacing inconsistencies become very visible.
- Free or budget fonts that lack comprehensive kerning tables.
- Mixing typefaces on the same line, such as pairing a serif with a sans-serif in a headline.
- Decorative or script fonts where the built-in metrics may not account for all stylistic variations.
- Logo design as a starting point before you apply manual kerning adjustments.
Practical Workflow: Headlines, Body Text, and Logos
Body Text
For paragraphs and running text, start with metric kerning. If you notice uneven spacing (which can happen with lower-quality fonts), switch to optical and compare. In most cases with a professional typeface, metrics will look better because the type designer optimized pair values for reading sizes.
Headlines and Titles
Large text magnifies every spacing flaw. Try optical kerning first for headlines, then compare with metrics. Optical kerning tends to produce tighter, more visually appealing spacing at display sizes. After selecting your preferred automatic method, manually adjust any pairs that still look off. Common trouble pairs include AV, To, LT, Yo, and WA.
Logo and Wordmark Design
Neither automatic method is sufficient on its own for logo work. Use optical kerning as your starting point because it adapts to the specific letterforms, then manually kern every single pair. Logo typography demands pixel-perfect spacing, and no algorithm can replace a trained eye at this level of detail.
Mixed Typeface Settings
Whenever you combine two different fonts on the same line, metric kerning cannot help you. The kerning tables in Font A know nothing about the characters in Font B. Switch to optical kerning for these situations, and add manual corrections as needed.
How to Change Kerning Settings in Popular Design Tools
Adobe InDesign
Select your text, then open the Character panel (Window > Type & Tables > Character). You will find a kerning dropdown that lets you choose between Metrics, Optical, or a manual numeric value. InDesign defaults to Metrics.
Adobe Illustrator
The process is nearly identical. Select your text, open the Character panel, and use the kerning dropdown. Illustrator also supports Metrics, Optical, and manual values.
Adobe Photoshop
In the Character panel, you will see the same kerning options. For most Photoshop text work (which tends to be headlines and display text), optical kerning is often the better starting point.
Figma
Figma does not expose a metric vs optical toggle in the same way Adobe tools do. It generally applies the font’s built-in kerning by default. For finer control, you will need to adjust letter spacing manually or use plugins designed for advanced typography.
Canva
Canva offers limited kerning control through its letter spacing slider. It does not provide a direct metric vs optical toggle. If precise kerning matters for your project, consider using a more advanced tool.
Common Kerning Mistakes to Avoid
- Leaving kerning set to “0” or “None” instead of choosing Metrics or Optical. This means no automatic kerning is applied at all, and your text will look unevenly spaced.
- Using metric kerning with low-quality free fonts. If the font has no kerning tables, the Metrics setting will do nothing, and your spacing will look random.
- Relying entirely on automatic kerning for logo work. Always finish logos with manual kerning adjustments.
- Confusing kerning with tracking. Tracking adjusts spacing uniformly across all characters. Kerning targets individual pairs. They serve different purposes and should be used independently.
- Not zooming in. Kerning issues are easy to miss at 100% zoom. Always check headlines and display text at a larger view before finalizing your design.
A Quick Decision Framework
When you are unsure which kerning method to use, run through these questions:
- Is the font from a professional foundry with good kerning tables? If yes, start with Metrics.
- Is the text set at a large display size (headlines, posters, banners)? Try Optical first.
- Are you mixing two different typefaces on the same line? Use Optical.
- Is this a logo or wordmark? Use Optical as a base, then kern manually.
- Is this body text in a long document? Use Metrics with a quality font.
Frequently Asked Questions
When should I use optical kerning vs metric kerning?
Use metric kerning for body text set in professional fonts with strong built-in kerning data. Use optical kerning for headlines, display text, mixed-font settings, or when working with fonts that have poor or missing kerning tables.
What does optical kerning actually do?
Optical kerning ignores the font’s internal spacing data and instead uses an algorithm to analyze the shapes of adjacent characters. It then calculates spacing values in real time to create visually even gaps between letters.
Is metric kerning always better than optical kerning?
No. Metric kerning is only as good as the kerning data embedded in the font file. If a font has incomplete or missing kerning tables, optical kerning will usually produce better results. Both methods have specific strengths depending on the context.
What are common kerning mistakes to avoid?
The most common mistakes include leaving kerning set to none, relying on metric kerning with poorly made fonts, skipping manual kerning on logos and headlines, and confusing kerning with tracking. Always visually inspect your text at multiple zoom levels.
Does kerning matter for web design?
Yes. While CSS does not offer a direct metric vs optical toggle, browsers apply the font’s built-in kerning by default through the font-kerning property. For web headlines where you need finer control, you may need to adjust letter-spacing on specific elements or use JavaScript-based solutions.
Can I combine optical kerning with manual adjustments?
Absolutely. In fact, this is the recommended workflow for display text and logos. Set the kerning method to Optical to get a solid baseline, then manually adjust individual letter pairs that still look unbalanced.
What is the difference between kerning and tracking?
Kerning adjusts the space between two specific characters. Tracking adjusts spacing uniformly across an entire range of selected text. You might use tighter tracking on a headline while still applying optical or metric kerning to fine-tune individual pairs within that headline.
Final Thoughts
The choice between optical kerning and metric kerning is not about one being universally better than the other. It is about understanding the strengths of each method and matching them to your specific design context. For body text with quality fonts, trust the type designer and use metrics. For headlines, mixed-font layouts, budget fonts, and logo work, optical kerning gives you a stronger starting point.
And no matter which automatic method you choose, remember that the best kerning is always finished by hand. Train your eye, zoom in, and take the time to adjust the pairs that matter most. Your readers may never consciously notice great kerning, but they will absolutely feel it.
