Email Subject Line Tester
Score your subject line for open rate, spam risk, and length
Type your subject line — see character count, mobile preview width, spam-trigger words, urgency score, and a 0–100 quality score. Optimised for Indian inboxes.
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What is an Email Subject Line Tester?
Subject lines decide whether your email gets opened. The average open rate across Indian B2B is 18-22%. Subject line is the single biggest lever — better than send time, better than from-name. Yet most teams spend 30 seconds writing it and move on.
This tester scores your subject line on the four signals that correlate with open rate: length (30-50 characters lands above the mobile clip line), spam trigger words (FREE, ACT NOW, GUARANTEED hurt deliverability), personalisation cues (first names lift open rate by 14%), and urgency (limited-time framing helps but only if it's real).
The output is a 0-100 score plus a per-signal breakdown so you know which knob to turn. Run 3-5 variants before sending — the best one usually wins by 3-8 percentage points on opens, which is real money on a 50,000-person list.
Why use this Email Subject Line Tester
Built for Indians, by Indians. Every number, every formula, every slab — tuned to FY 2026-27 reality.
Length and clip preview
See how your subject renders on mobile (Gmail clips at ~35 chars on iPhone). Avoid the dreaded "..."
Spam-word detection
Flags words and phrases known to trigger Gmail/Outlook spam filters.
Personalisation check
Detects merge tags ({first_name}) and the use of "you" — both correlate with higher open rates.
Urgency signal
Detects time-bound phrasing. Flags overuse — if every email is "last chance", subscribers stop believing.
Private
No subjects sent to a server. All scoring runs in-browser.
Using the Email Subject Line Tester in 4 steps
No onboarding, no signup. Answer three fields and the numbers update live.
Type your subject line
Or paste a draft from your ESP. Score updates live.
Read the score breakdown
See length, spam risk, personalisation, urgency — each scored 0-100.
Tune the weak signals
Long? Trim. Has "FREE"? Replace with "complimentary" or restructure. No personalisation? Add merge tag.
A/B-test the top 2 in your ESP
Don't pick a winner from the score alone. Send to 10% of your list as A/B, deploy the winner to the rest.
Tips to get the most out of it
Mobile preview clips at ~35 chars on iPhone Gmail. If your subject is 45 chars, the most important info should be in the first 35.
Avoid ALL CAPS — it reduces open rate by 30% on average and triggers some spam filters. Use sentence case for everything except acronyms.
Emoji sparingly. One well-placed emoji (📩, 💡) lifts open rate; two or more flags as promotional and gets filtered to the Promotions tab on Gmail.
Test from-name as well — it has even higher impact than subject. "Bizeract" beats generic noreply addresses by 12+ percentage points.
Real-world scenarios
How Indians actually use this tester — concrete inputs, concrete outcomes.
B2B nurture sequence
Marketer drafts "FREE GST Registration Guide - Limited Time Only!". Score: 38 (caps, spam triggers, no personalisation). Tweaks to "{first_name}, here's the GST guide we promised". Score: 86. Open rate jumps from 22% to 31%.
Founder broadcast
Founder writes a personal-style update. Tests 3 subject variants in this tool, picks the highest-scoring "Quick update on Q1 (3 things)". Hits 47% open rate vs. previous 28%.
Cart abandonment
E-commerce sends "You left items in your cart". Tester suggests adding personalisation: "{first_name}, your cart is waiting". Open rate climbs by 16%.
Frequently Asked Questions
Still have a question? Our team replies within a business day.
It correlates strongly with open rate but doesn't replace A/B testing. Use it to filter out weak variants before testing the top 2.
"FREE" in subject lines is one of the strongest spam-filter triggers. It also signals discount-bait to readers, lowering the conversion quality even when opened.
A single emoji can lift opens by 5-10% in B2C. In B2B (especially Indian B2B), too many emojis read as unprofessional. Test for your audience.
Yes. Click-through-rate-from-open drops sharply if the subject overpromises. Tester's "urgency" check helps catch overhype.
Gmail has stricter ML-based filters; Outlook uses keyword-based rules. The tester checks against both. If a word is on either list, it's flagged.
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