Email Subject Line Character Limits
Your email subject line is the first thing recipients see — and it determines whether they open your message or scroll past it. Different email clients and devices display varying numbers of characters before truncation with "..." This reference table shows exactly how many characters display across Gmail, Outlook, Apple Mail, Yahoo, mobile apps, and wearables.
When You Need This Table
- Crafting email marketing campaigns with high open rates
- Writing subject lines for newsletters that display fully on mobile
- Optimizing transactional emails for readability
- A/B testing subject line lengths across different audiences
- Ensuring important information isn't cut off on small screens
| Email Client | Desktop | Mobile App | Mobile Web |
|---|---|---|---|
| Gmail | 70+ | 40-45 | 30-35 |
| Outlook Desktop | 60 | 35-40 | 35 |
| Apple Mail (macOS) | 78 | 35 | 35 |
| Yahoo Mail | 47 | 35 | 35 |
| AOL Mail | 45 | 35 | 35 |
| iPhone Mail App | N/A | 30-35 | 30 |
| Android Gmail | N/A | 40-45 | 30 |
| Samsung Email | N/A | 35 | 35 |
| Apple Watch | N/A | 18-20 | N/A |
Key Takeaways
- Mobile shows 30-45 characters — front-load important words
- Apple Watch shows only 18-20 characters
- Desktop clients show 60-78 characters on average
- The safest length is under 40 characters for universal visibility
Subject Line Best Practices
- Put the action or benefit first
- Avoid all caps and excessive punctuation (spam triggers)
- Personalization increases open rates by 26%
- Test emojis carefully — they can boost or hurt engagement
Optimizing Email Subject Lines for Mobile
Over 60% of emails are now opened on mobile devices, making mobile optimization critical for email marketing success. The biggest challenge? Mobile email apps typically show only 30-45 characters of your subject line, compared to 60-78 on desktop.
The solution is front-loading: put your most important words — the action, benefit, or hook — in the first 30 characters. Think of it as writing a headline within a headline. "50% Off Ends Tonight" works better than "Don't Miss Our Amazing Sale — 50% Off Everything!"
Preview text (preheader) is equally important. Most mobile clients show 40-90 characters of preview text after the subject line, effectively doubling your real estate. Use it strategically to complement your subject rather than repeat it.
Why Character Limits Matter for Email Marketing
Email clients truncate subject lines differently based on screen size and platform, which can lead to critical information being cut off. For example, while Gmail displays 70+ characters on desktop, it only shows 30-35 characters on mobile web. This discrepancy means a subject line that looks complete on your computer might appear truncated on a smartphone. Recipients are more likely to open emails when the full message is visible, making character limits a crucial consideration for open rates. Shorter subject lines also perform better on wearables like the Apple Watch, which only displays 18-20 characters. Understanding these limits helps marketers craft subject lines that remain effective across all platforms, ensuring key messages like discounts, deadlines, or event details aren't lost in truncation.
Best Practices for Writing Within Character Limits
To maximize visibility across email clients, aim for subject lines under 35-40 characters. This ensures full display on most mobile apps, where the majority of emails are opened. Prioritize clarity and urgency in the first 25 characters, as this is typically the threshold before truncation on smaller screens. Use abbreviations sparingly—while they save space, overuse can reduce readability. Avoid unnecessary words like 'the' or 'and' to stay within limits. For time-sensitive campaigns, place deadlines or countdowns near the beginning. Test subject line lengths using tools like Litmus or Email on Acid to preview how they appear across clients. Finally, consider using emojis strategically; they count as multiple characters but can increase open rates when used appropriately. These practices ensure your subject lines remain both compliant with platform limits and compelling to recipients.
Mobile vs. Desktop: Key Differences in Display
Mobile and desktop clients often handle subject line display differently. Desktop clients like Apple Mail (macOS) show up to 78 characters, allowing more flexibility for detailed messaging. However, mobile apps such as the iPhone Mail App only display 30-35 characters, significantly limiting what recipients see. This disparity is particularly important for transactional emails, where critical information like order confirmations or delivery dates must remain visible. Wearables like the Apple Watch further constrain display to just 18-20 characters, requiring ultra-compact subject lines for alerts and notifications. Marketers should prioritize mobile-first subject line design, as over 60% of emails are opened on mobile devices. Testing across platforms using real-world scenarios can reveal how truncation impacts readability, helping you optimize for both length and clarity across all devices.