1Pick a scenario
Cold email, sales, follow-up, meeting request or formal business — each has its own proven patterns.
Free business email subject line generator
Business email subject lines
Business email subject lines
that get opened
Generate clear, professional business email subject lines and score your own for length and deliverability — instantly. Free, no sign-up.
No sign-up required
Spam-word check
Instant scoring
A great subject line is wasted on the wrong list.
Flow AI finds your ideal buyers and runs personalised email and LinkedIn outreach on autopilot — with built-in daily limits and human-like pacing that protect your domain and reputation.
Start free in Flow AIBusiness subject lines that respect everyone's time
Internal and professional business emails are read by colleagues, managers and clients who scan dozens of threads a day. Clarity beats cleverness: the subject line is a label that tells the reader what the email is and what, if anything, they need to do with it.
State the topic plainly and front-load any action. Lines like "Q3 budget review — your sign-off needed by Friday", "Agenda: Thursday client kickoff" or "Updated contract attached for signature" let busy people triage at a glance and find the thread again later. Use a tag such as "FYI", "Action required" or "Decision needed" when it genuinely helps, and keep tone professional rather than promotional.
- Lead with the subject of the email, then the specific ask or deadline.
- Use clear status tags so threads stay easy to search and triage.
- Skip vague lines like "Update" or "Touching base" that say nothing at all.
Better subject lines in seconds
The subject line decides whether your email gets opened or ignored. Get it right.
2Generate & tweak
Add what it's about and get a set of options, each scored for length and deliverability. Copy your favourite.
3Test your own
Paste any subject line to grade it instantly — length, word count, spam triggers, caps and punctuation.
What makes a subject line work
Short & mobile-first
Most inboxes cut off around 50–60 characters. Lead with the part that earns the open.
Specific, not salesy
Spam-trigger words and ALL-CAPS hurt both opens and deliverability. The tester flags them for you.
Curiosity + relevance
The best lines hint at something useful and specific to the reader, without giving everything away.
Frequently asked questions
Win the open. Then let Flow AI win the reply.
No credit card required