Free AI Email Subject Line Generator

Generate compelling email subject lines that get opened. Our AI crafts multiple subject line variations using proven copywriting techniques — urgency, curiosity, personalization, and power words — all for free.

47%

of emails opened based on subject line alone

10–15%

average open rate lift with optimized subject lines

unique variations generated per request

What is your email about?*

Industry*

Tone*

Email Type*

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サンプル結果

例 1

email_purpose: 48-hour flash sale with 30% off all products for existing customersindustry: ecommercetone: urgentemail_type: promotional

1. Subject: ⏰ 48 hrs left: 30% off everything
Preheader: Your exclusive sale ends tomorrow at midnight — don't miss it.
Why it works: The clock emoji creates immediate visual urgency, and the specific "48 hrs" is more credible than vague deadlines like "limited time."

2. Subject: We saved something for you (ends soon)
Preheader: 30% off — but only for our loyal customers this weekend.
Why it works: The curiosity gap ("something for you") combined with the exclusivity signal drives opens without sounding like a generic blast.

3. Subject: Your 30% off code expires in 2 days
Preheader: This deal is exclusive to customers who've shopped with us before.
Why it works: Personalization framing ("your code") makes it feel individually addressed, increasing perceived value and urgency.

4. Subject: Exclusive: 30% off your next order
Preheader: Flash sale — every product, every category, no exclusions.
Why it works: "Exclusive" is a proven power word that signals insider access and elevates perceived offer quality.

5. Subject: 3 reasons to shop this weekend
Preheader: 30% off sitewide, free shipping, and a surprise gift at checkout.
Why it works: Number-led subject lines set a clear expectation and curiosity about what the three reasons are.

6. Subject: Still thinking about that item you loved?
Preheader: Now's the time — it just got 30% cheaper for the next 48 hours.
Why it works: The question format addresses purchase hesitation directly, making the reader feel understood rather than sold to.

例 2

email_purpose: Monthly product update newsletter featuring three new features in our project management SaaSindustry: saastone: friendlyemail_type: newsletter

1. Subject: 3 new features dropped this month 🚀
Preheader: Here's what we shipped in January — and what's coming next.
Why it works: The specific number "3" sets a concrete expectation, and "dropped" uses product-world language that resonates with tech-savvy SaaS audiences.

2. Subject: Your workflow just got a lot smoother
Preheader: We listened to your feedback and built exactly what you asked for.
Why it works: The curiosity gap keeps readers wondering what changed, while speaking directly to their pain point (workflow friction).

3. Subject: What's new at [Product] this month
Preheader: Three features our most active teams are already loving.
Why it works: Simple and honest — no clickbait. Works well for established newsletter subscribers who trust the brand and open regularly.

4. Subject: Big update: your team will thank you
Preheader: Collaboration, automation, and reporting — all upgraded this month.
Why it works: "Your team will thank you" shifts the value proposition from features to outcomes and creates social proof via implied praise.

5. Subject: We shipped 3 things you've been asking for
Preheader: See what's live — takes less than 3 minutes to read.
Why it works: Directly acknowledges user feedback, building trust and making the reader feel heard. The time estimate removes friction.

6. Subject: Can your tool do this now? Ours can.
Preheader: Three new features live in your dashboard right now.
Why it works: The competitive question sparks curiosity and pride, nudging the reader to discover what capability they now have.

例 3

email_purpose: Inviting prospects to an open house for a new luxury condo development this Saturdayindustry: real_estatetone: personalizedemail_type: promotional

1. Subject: You're invited: Saturday open house 🏡
Preheader: Exclusive preview of our newest luxury condos — RSVP to save your spot.
Why it works: "You're invited" creates a personalized, exclusive feeling that distinguishes this from a mass announcement and increases open rate.

2. Subject: Something new is happening on Saturday
Preheader: We thought of you when this listing opened — come see it in person.
Why it works: The vague "something new" creates a curiosity gap, while the personal touch ("we thought of you") builds relationship equity.

3. Subject: The unit you've been waiting for is ready
Preheader: Join us Saturday for a private preview before it goes public.
Why it works: Speaks directly to buyer intent and urgency — "before it goes public" adds genuine scarcity that feels authentic rather than manufactured.

4. Subject: Inside look: Luxury condos opening Saturday
Preheader: Private tour, complimentary refreshments, and your questions answered live.
Why it works: "Inside look" implies privileged access. Listing the event details in the preheader converts readers who are on the fence about attending.

5. Subject: 48 hours to see it before anyone else
Preheader: Exclusive open house Saturday — only 12 tour slots available.
Why it works: Combining a countdown with a specific capacity limit ("12 slots") creates authentic scarcity far more effectively than generic urgency language.

6. Subject: Is this the home you've been searching for?
Preheader: Find out Saturday — open house 10am–4pm, refreshments included.
Why it works: The question invites self-reflection and speaks to the emotional aspiration behind property searching, not just the logistics.

使い方

Describe Your Email

Tell us what your email is about — the offer, announcement, or message you want to communicate to your subscribers.

Set Your Parameters

Select your industry, desired tone, and email type so the AI crafts subject lines tailored to your exact audience and goals.

Test & Send

Get 6 subject line variations with preheader suggestions. A/B test two variations in your email platform for best results.

Why Your Email Subject Line Is Your Most Important Copy

In 2026, the average office worker receives over 120 emails per day. Your subject line has approximately 2 seconds to compete with every other message in the inbox. According to Campaign Monitor data, 47% of email recipients open an email based on the subject line alone — making it the single highest-leverage piece of copy in your entire email marketing strategy.

A weak subject line means even the best email content never gets read. Our free AI email subject line generator solves this by producing multiple high-converting variations using proven copywriting frameworks, personalization techniques, and platform-tested language patterns.

What Makes an Email Subject Line Convert in 2026

The principles behind high-performing subject lines have stayed consistent even as inboxes have become more crowded. The best subject lines share five characteristics:

Specificity over vagueness — "Save 30% on running shoes this weekend" dramatically outperforms "Big sale happening now." Specific claims are more believable and create a clearer reason to open.
A single emotional trigger — Whether it is urgency, curiosity, exclusivity, or empathy, effective subject lines activate one primary emotion rather than trying to do everything at once.
Optimal character count — Subject lines between 30 and 50 characters perform best across devices. Most email clients truncate at around 60 characters on desktop and as few as 30 characters on mobile.
Preview text alignment — The preheader (the preview text that appears next to or below the subject line) should extend the subject line story, not repeat it. Together they form a two-part hook.
Spam filter compliance — Excessive capitalization, multiple exclamation marks, and phrases like "ACT NOW!!!" trigger spam filters before your email even reaches the inbox.

Email Open Rate Benchmarks by Industry (2026)

Understanding what constitutes a good open rate in your industry is the foundation of knowing whether your subject lines are working. According to Mailchimp's 2026 industry benchmarks:

Real estate — Average open rate of 19.7%, making personalized subject lines especially high-impact in this sector
E-commerce — Average open rate of 15.6%, where urgency and promotional language consistently outperform generic announcements
SaaS and technology — Average open rate of 21.9%, where educational subject lines and feature announcements drive strong engagement
Restaurants and food service — Average open rate of 19.8%, where sensory language and time-limited offers perform particularly well
Fitness and wellness — Average open rate of 20.4%, where transformation language and community-oriented subject lines lead

Power Words That Boost Email Open Rates

Certain words and phrases have been proven through large-scale A/B testing to increase open rates. Incorporating them naturally — without overpromising — is a reliable technique for improving performance.

Exclusivity words: exclusive, private, members-only, insider, VIP, reserved for you
Urgency words: expires, deadline, last chance, today only, ending soon, hours left
Curiosity words: secret, revealed, what nobody tells you, the truth about, here is why
Personalization hooks: your, you, for you, based on your, we noticed you
Value signals: free, save, bonus, gift, complimentary, no cost

A/B Testing Email Subject Lines: A Practical Framework

Generating multiple subject line variations with our tool is only the first step. Systematic A/B testing turns those variations into a continuous improvement engine for your email program. Here is a simple framework:

Test one variable at a time — Compare two subject lines that differ in exactly one element: length, tone, the presence of an emoji, or the emotional trigger used. Testing multiple variables simultaneously makes it impossible to identify what actually drove performance change.
Use a sufficient sample size — A list of under 1,000 subscribers will not produce statistically significant results. Most email platforms require a minimum of 500 recipients per variant to generate meaningful data.
Measure beyond open rate — Open rate measures subject line effectiveness, but click-through rate measures content effectiveness. A subject line that generates high opens but low clicks may be misleading or mismatched with the email body.
Build a swipe file — Keep a running record of your winning subject lines along with the context (industry, list segment, send time, seasonal timing) so you can identify patterns over time.

Emoji Usage in Email Subject Lines

Emojis in subject lines can increase open rates by 10 to 15% when used appropriately. The key word is appropriately. Emojis work best when they replace or emphasize a word rather than decorate arbitrarily. A clock emoji before a countdown communicates urgency faster than the word "urgent" itself. A house emoji in a real estate subject line is contextually relevant and adds visual differentiation in a crowded inbox.

Avoid using multiple emojis in a single subject line, and never lead with an emoji unless you have tested it with your specific audience. B2B audiences, in particular, often respond negatively to heavy emoji use in professional contexts.

Personalization Techniques That Go Beyond First Names

First-name personalization was revolutionary in 2015. In 2026, subscribers are accustomed to it and its impact on open rates has diminished. Modern personalization in subject lines goes deeper:

Behavior-based triggers — "We noticed you browsed [category]" or "Picking up where you left off?" reference specific actions the subscriber has taken
Location references — "Open houses near [City] this weekend" creates geographic relevance that general subject lines cannot replicate
Purchase history signals — "It is time to restock your [previous product]" demonstrates that you understand individual customer patterns
Milestone acknowledgments — "Happy one year with us — here is something special" rewards loyalty and drives emotional connection

よくある質問

How many subject lines does the generator create?

The generator produces 6 subject line variations per request, each using a different proven copywriting technique — urgency, curiosity gap, personalization, power words, numbers, and question format. Each variation also includes a preheader text suggestion and an explanation of why it works.

What is the ideal email subject line length?

Research consistently shows that subject lines between 30 and 50 characters achieve the highest open rates. This length displays fully on most mobile devices (which account for over 60% of email opens in 2026) and on desktop clients. Our generator automatically targets this range while ensuring the subject line communicates the core message clearly.

Should I use emojis in my email subject lines?

Emojis can increase open rates by 10-15% when used contextually and sparingly. They work best for B2C audiences in industries like e-commerce, restaurants, fitness, and lifestyle brands. For B2B audiences, especially in professional sectors like finance, legal, or enterprise SaaS, emojis in subject lines can reduce credibility. Test with your specific list to see what resonates.

How do I avoid the spam folder?

Spam filters flag subject lines containing all-caps words, excessive punctuation (!!!), misleading clickbait phrases, and certain trigger words like "free money" or "act now." Our AI generator is trained to avoid these patterns. Beyond the subject line, deliverability depends on sender reputation, list hygiene, authentication records (SPF, DKIM, DMARC), and engagement history with your list.

How should I A/B test subject lines?

Send variant A to 25% of your list and variant B to another 25%, using open rate as the metric. After 2-4 hours, send the winning variant to the remaining 50%. This approach, supported by most major email platforms like Mailchimp, Klaviyo, and HubSpot, lets you optimize every send while still reaching your full list. Only change one element between variants — tone, length, or the presence of an emoji — to isolate the variable that drives results.

Does this tool work for cold email subject lines?

Yes, the generator works for cold outreach as well as permission-based email marketing. For cold email, select the "professional" tone and "follow-up" email type, then focus your email purpose description on the specific value proposition relevant to the prospect. Cold email subject lines generally perform best when they are highly specific, short (under 40 characters), and avoid the promotional language used in newsletter or sales campaigns.

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