Cycling through all six. Tap any point to stop.

Measured on six things

Security

Local-only processing is a real privacy win, but the probe found HTTPS not enforced and zero of the standard security headers (no HSTS, CSP, frame protection, or Referrer-Policy). No security page or audit.

Screenshots

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LinesDeduplicate

About this app

LinesDeduplicate is a free online tool that removes duplicate lines from any list — emails, keywords, logs, or CSV exports. Paste on the left, get unique lines on the right. Everything runs in your browser with JavaScript; nothing is uploaded. No account, no watermarks; optional ignore-case and trim. Pricing: Free. Founder: Keith Zhong. Country: China. Contact: info@linesdedupe.com. GitHub: https://github.com/kitorz/linesdedupe

Key features

1Browser-only deduplication — nothing uploaded, no account required.
2Options for ignore-case, trim spaces, blank lines, keep first/last, and sorting.
3Copy or download unique lines as .txt, with keyboard shortcuts and a Load example button.

Target customer profile

Drawn from the product itself, not from a survey.

Demographic

Marketing professionals managing email campaigns

Pain points

Duplicate emails cause wasted sends and skewed metrics

Primary needs

Quickly dedupe email lists without uploading sensitive data

Demographic

SEO specialists and content marketers

Pain points

Keyword lists get messy with repeats from multiple sources

Primary needs

Clean and sort keyword lists efficiently in-browser

Demographic

Developers and data analysts

Pain points

Log files and CSV exports contain redundant lines that clutter analysis

Primary needs

Fast, local deduplication of text data without installing software

Scout Review

Written by AI from measured evidence, scored out of 100.

LinesDeduplicate is a focused, genuinely useful free utility: paste a list, get unique lines, nothing uploaded. Usability and accessibility are strong, desktop speed is excellent, and the privacy-first, no-account approach is a real differentiator against server-upload competitors. The gaps are security hardening (no enforced HTTPS, no security headers) and a commodity niche with thin growth headroom. For a quick, private dedupe, it does the job well.

Measure by measure

Usability

Paste-to-result with no signup, a Load example button, keyboard shortcuts, and an inline 3-step guide plus FAQ. Onboarding is essentially instant; docs are thin but the tool is self-explanatory.

Design

Clean, purposeful single-page tool: bold headline, side-by-side paste/output panes, and a tidy options row. Functional and modern enough, though visually plain and text-heavy below the fold.

Speed

Desktop Lighthouse 99/100 and client-side dedupe with no server round-trip. Mobile drops to 75/100 with a 5.1s LCP, so the first paint on phones is the weak link.

Security

Accessibility

Lighthouse accessibility 96/100 with keyboard shortcuts and a simple single-page layout. One failing audit: insufficient color contrast. No WCAG statement or multi-language support found.

Growth

Real recurring chore with a clear privacy wedge (in-browser, no upload) against Browserling's server upload. Free and no-account, but a crowded commodity niche with thin monetization headroom.

Improvement areas

Security hardening: enforce HTTPS and add HSTS, CSP, and frame-protection headers.
Mobile performance: reduce the 5.1s LCP on phones.
Accessibility: fix the color-contrast failing audit and add a WCAG statement.

Design & Usability

LinesDeduplicate is a single-purpose tool that knows exactly what it is. The landing page leads with a bold 'REMOVE DUPLICATE LINES. QUIETLY.' headline over a two-pane paste/output layout, with an options row for ignore-case, trim, blank lines, keep-first/last, and sorting. Usability is the standout: paste on the left, results on the right, no signup, a Load example button, and keyboard shortcuts (⌘/Ctrl+Enter to dedupe and copy). The inline three-step guide and 'Is my list uploaded?' FAQ cover the basics without bloat. Design is clean but plain — functional rather than crafted, with a text-heavy lower page. For a free utility, the friction is close to zero, which is the whole point.

Speed & Security

Speed is split by device: desktop Lighthouse scores 99/100 with CLS 0 and TBT 37ms, while mobile lands at 75/100 with a 5.1s LCP and 2.6s FCP. Because deduplication runs client-side in JavaScript, there is no per-operation network round-trip — the tool feels instant once loaded. Security is the weak dimension. The HTTP probe found HTTPS not enforced and none of the standard hardening headers (no HSTS, CSP, frame protection, X-Content-Type-Options, Referrer-Policy, or Permissions-Policy), scoring 1/12 on the checklist; SPF is present but DMARC is not. The local-only processing claim is a genuine privacy advantage, but there is no security page, audit, or policy depth to back it up.

Accessibility & Growth

Accessibility scores well: Lighthouse 96/100, with one failing audit for insufficient color contrast. Keyboard shortcuts and a simple single-page layout help, though there is no WCAG statement or multi-language support. Growth is a judgement on the idea: deduping email lists, keyword lists, logs, and CSV exports is a real, recurring chore, and the privacy wedge — everything runs in-browser with nothing uploaded — is a concrete reason to pick it over Browserling, which requires a server upload. TextFixer is the closest free peer. But this is a crowded commodity niche with no obvious monetization path, so the idea can win users without building much of a moat.

Conclusion

If you need to strip duplicates from an email list, keyword set, or log export without handing your data to a server, this is a solid, no-friction choice. It is not trying to be a platform — it is a sharp little tool that respects your privacy and your time. Fix the HTTPS enforcement and headers, and it becomes easy to recommend without caveats.

Suggestions for improvement

Enforce HTTPS and add HSTS, CSP, and frame-protection headers to match the privacy promise.
Improve mobile LCP (5.1s) by trimming render-blocking resources and optimizing first paint.
Fix the color-contrast failing audit and publish a short accessibility statement.
Add a brief security/privacy page explaining the local-only processing model.

How we score

Alternatives comparison

Named competitors, point by point. Nobody paid to appear here or to be left out.

	LinesDeduplicate	TextFixer	Browserling
Price	Free	Free	Free (with limits)
Data privacy (local vs. server processing)	Runs entirely in-browser; nothing uploaded	Client-side processing	Requires uploading text to their server
Case sensitivity & sorting options	Ignore case, trim, blank lines, keep first/last, sort A→Z / Z→A	Case sensitivity and sorting options	Basic dedupe options
Account required	No	No	No