Email Subject Line Tester
Free to download on every platform. Comes pre-installed on BotFone, BotPad and BotFlip — with extra free apps included.
About this app
WHAT IT DOES
The Email Subject Line Tester scans the current page for text input fields and textareas that are likely email subject line fields—based on name, ID, placeholder, or aria-label containing "subject" or "title". It displays a real-time overlay showing character count, word count, and remaining characters relative to common email platform limits: Gmail (70 chars), Outlook (60 chars), Apple Mail (70 chars), and a general best practice of 50 chars. The overlay is color-coded: green for within limits, yellow for approaching, red for exceeded. It also flags potential issues like all‑caps words and common spam trigger words (free, urgent, guaranteed, limited time, etc.)—helping copywriters craft subject lines that are both effective and deliverable.
WHERE IT RUNS
It runs as a draggable overlay panel inside the BotGentz extension on any website—email marketing platforms (Mailchimp, SendGrid, Klaviyo), CRM systems, newsletter builders, or any page with a subject line field. It works on any framework (React, Vue, Angular, vanilla HTML).
HOW TO USE
1. Install the free BotGentz extension.
2. Navigate to any page with an email subject line field.
3. Click the BotGentz icon and select "Email Subject Line Tester" from the tools menu.
4. Click "Start Watching" to begin monitoring subject line fields.
5. Type in a subject line field—an overlay appears showing character count, word count, and remaining characters.
6. Select your target platform from the settings to apply the correct limit.
7. Customize the limit with the custom option.
8. Toggle word count, remaining characters, and spam flagging in settings.
9. Click "Refresh" to update overlays if new fields appear.
10. Click "Stop" to remove overlays and stop monitoring.
11. Drag the panel to reposition it, resize it, collapse it, or press Escape to close.
THE ACTUAL MECHANISM — intelligent field detection with multi‑platform limit overlays and spam word detection
This tool scans the DOM for text inputs and textareas using a heuristic detection algorithm: it checks name, ID, placeholder, className, and aria‑label for keywords "subject" or "title". For each detected field, it creates a fixed‑position overlay above the field using the field's bounding client rect. The overlay displays: character count (with color coding), word count, remaining characters, and the current platform label. The tool also checks the subject text against a built‑in list of common spam trigger words and detects all‑caps words (words longer than 3 characters that are fully uppercase). Issues are flagged with a warning icon and tooltip. Event listeners are attached to each field so overlays update on every keystroke. A MutationObserver watches for new fields added dynamically. All limits and settings are stored via GM_setValue and applied globally.
THE PANEL
The panel is fully draggable by its title bar and snaps to the nearest edge of the viewport when released. You can resize it horizontally by dragging the left or right border; the height expands to fit content up to a maximum, with scrolling inside the settings area. A collapse button minimizes the panel to a small floating chip showing "⚙️ Subject Tester" — click it to expand back. Press Escape at any time to close the panel entirely. The panel remembers its last position, size, and expansion state per domain via localStorage.
PLEASE NOTE
- This tool requires the free BotGentz extension (available for Chromium‑based browsers and Firefox).
- The tool detects subject line fields heuristically—if a field is not detected, it may not be a standard subject line field.
- Character counting includes spaces and punctuation, matching most email platform counting methods.
- Spam word detection is based on a common list—it is not exhaustive and should be used as a guideline, not a definitive filter.
- No page content is ever sent to any server—all counting and detection happens locally in your browser. Only anonymized usage metrics (panel open/close, platform selections) are collected; you can disable this in the extension settings at any time.
Similar Apps
