How I Built a Privacy-First Word Counter Chrome Extension (with CJK Support)

Boris Korolev — Mon, 18 May 2026 15:12:59 +0000

I’ve always been frustrated with online word counters.

You copy text, paste it into a random website, and hope it doesn’t store your content or track you. For writers, editors, and students who work with sensitive drafts, that’s a real problem.

So I built Instant Word Counter — a Chrome extension that counts words, characters, and reading time instantly, offline, and 100% locally. No text ever leaves your device.

Why another word counter?

Most existing extensions either:

require copy-pasting,
use clunky right-click menus,
or send your text to external servers for processing.

I wanted something faster and truly private.

How it works

Select any text on a webpage.
Click the extension icon (or press Alt+W).
See word count, character count (with/without spaces), and estimated reading time in a clean popup.

If no text is selected, the extension gently guides you. No clutter, no confusion.

CJK character counting

One feature I’m especially proud of: the extension correctly handles Chinese, Japanese, and Korean (CJK) characters. When CJK characters are detected, it automatically switches from "Words" to "CJK Characters" — something most word counters get completely wrong.

It uses the Intl.Segmenter API for word segmentation and falls back to a regex-based counter for older browsers.

Tech stack

Vanilla JavaScript (no frameworks)
Chrome Manifest V3
Intl.Segmenter for accurate word counting
chrome.i18n for localization (10 languages so far)
All processing happens locally — no backend, no analytics, no tracking

Privacy by design

No data collection
No network requests
No cookies
The extension only requests activeTab and scripting permissions — nothing else

What I learned

Intl.Segmenter is powerful but still limited for mixed-language texts
Chrome Web Store localization is surprisingly tricky (detailed descriptions must be added manually per language)
Users genuinely care about privacy — several early reviews mentioned it as the main reason for installing

Try it out

Instant Word Counter is free and available on the Chrome Web Store.

Happy to answer questions or hear your feedback in the comments!

DEV Community: Boris Korolev

How I Built a Privacy-First Word Counter Chrome Extension (with CJK Support)