Email Subject Line Length: Best Practices for 2026

Your email subject line is the first thing recipients see—and often the deciding factor in whether they open your email or ignore it. Getting the length right is crucial for visibility and engagement.

This guide covers optimal subject line lengths for different devices, email clients, and use cases, backed by data and real-world best practices.

Character Limit Overview

Ideal Subject Line Length

Based on extensive research and testing:

• Sweet spot: 30-50 characters (4-7 words)
• Mobile-first: Under 35 characters for full mobile visibility
• Maximum recommended: 60 characters (avoids truncation on most clients)

Why This Range Works

1. Mobile visibility: Over 60% of emails are opened on mobile devices
2. Curiosity gap: Short enough to be intriguing, long enough to convey value
3. Preheader space: Leaves room for supplementary preview text
4. Scan-friendly: Readers can process the entire subject at a glance

Open Rate by Length

Desktop vs Mobile Display

Mobile Considerations (Priority)

With mobile opens dominating email, optimize for smaller screens first:

• iPhone Mail: Shows ~35-38 characters
• Gmail App: Shows ~40 characters
• Android varies: 33-43 characters depending on device

Rule of thumb: Put your most important words in the first 30 characters.

Desktop Considerations

Desktop clients show more but still truncate:

• Gmail web: Up to 70 characters (varies by screen width)
• Outlook desktop: Up to 73 characters
• Apple Mail desktop: Up to 78 characters

By Industry & Email Type

E-commerce

• Promotional: 30-40 characters (urgency-focused)
• Cart abandonment: 25-35 characters (direct)
• Order confirmation: 40-50 characters (informative)

B2B / Professional

• Outreach: 40-50 characters (personalized)
• Newsletters: 40-60 characters (descriptive)
• Follow-ups: 30-40 characters (brief)

SaaS / Tech

• Onboarding: 35-45 characters
• Feature updates: 40-55 characters
• Re-engagement: 25-35 characters

Best Practices

Writing Effective Subject Lines

1. Front-load key words: Put the most important information first
2. Be specific: Vague subjects get ignored
3. Create urgency (sparingly): Use time-sensitive language when appropriate
4. Personalize: Include recipient's name or relevant details
5. Avoid spam triggers: ALL CAPS, excessive punctuation!!!, "FREE"
6. Test with preheader: Consider how subject + preheader work together

Preheader Text

The preheader (preview text) appears after your subject line:

• Optimal length: 85-100 characters
• Purpose: Extend or complement your subject line
• Don't repeat: Add new information, don't echo the subject

What to Avoid

• Generic subjects like "Newsletter #47"
• Misleading clickbait that doesn't match content
• Excessive emojis (1-2 max, test first)
• Repeating sender name in subject
• Overused phrases ("Don't miss out!", "Act now!")

High-Converting Examples

E-commerce (30-40 chars)

• "Your cart misses you" (19 chars)
• "24 hours left: 40% off everything" (35 chars)
• "New arrivals you'll love" (25 chars)

B2B (40-50 chars)

• "Quick question about your Q4 goals" (35 chars)
• "[Name], saw your recent post on LinkedIn" (41 chars)
• "3 ways to reduce customer churn" (32 chars)

Newsletters (40-55 chars)

• "This week: AI trends you need to know" (38 chars)
• "The one metric that predicts success" (37 chars)
• "5 lessons from our $1M launch" (30 chars)

Frequently Asked Questions

What is the ideal email subject line length?

The ideal email subject line length is 30-50 characters (or 4-7 words). This range ensures visibility across both desktop and mobile devices while leaving room for preheader text to display.

How many characters can an email subject line be?

Most email clients have no hard character limit for subject lines. However, Gmail cuts off subjects around 70 characters on desktop and 30-40 on mobile. For maximum visibility across all devices, aim for under 50 characters.

Does subject line length affect open rates?

Yes, subject line length significantly impacts open rates. Research consistently shows that subject lines with 6-10 words (roughly 30-50 characters) tend to have the highest open rates. Subject lines that are too short may lack context, while those that are too long get truncated on mobile.

What is the preheader text limit?

Preheader text (also called preview text) should be 40-130 characters. Most mobile clients display 35-90 characters depending on how long your subject line is. For optimal display across devices, aim for 85-100 characters of preheader text.

Should I use emojis in email subject lines?

Emojis can increase open rates when used appropriately, but results vary by audience and industry. Limit to 1-2 emojis, place them strategically, and always A/B test. Note that emojis may display differently across email clients.