Duplicate Line Remover — Dedupe Text Lines

Cat command merges, spreadsheet copy errors, and repeated API pagination fetches append duplicate rows. Scripts expecting uniq fail or analytics double-count events.

Manual eyeballing thousand-line lists misses duplicates — automated line dedupe collapses noise in seconds.

Keep first retains earliest occurrence — useful when first seen timestamp or order matters in log chronology. Keep last keeps newest duplicate — handy when later lines contain corrected values in iterative paste.

Choose policy before dedupe — output order of survivors reflects first-seen sequence when keeping first.

Two lines match when strings are identical including whitespace unless trim option exists. CR versus LF line endings may make visually identical lines differ — normalize line endings externally.

Case differences create distinct lines — User and user survive both when case-sensitive.

Marketing exports dedupe before Mailchimp import to avoid double sends. Security allowlists dedupe IP rows before sort and diff against baseline.

Survey free-text answers dedupe for frequency analysis — fuzzy matching still needs separate tools.

Stack trace lines repeated in loop output collapse to unique messages for error grouping. Keep last when final line includes latest retry count suffix.

Pair with regex-tester to extract field before dedupe when duplicates differ only by timestamp prefix.

Email and username lists dedupe locally — critical for GDPR-conscious workflows avoiding third-party upload.

Clear workspace after processing subscriber exports on shared PCs.

Sort then dedupe and dedupe-with-sort toggle overlap — use line-sorter when alphabetical order is primary goal with optional unique. Use duplicate-line-remover when order must stay insertion-relative with explicit keep-first or keep-last.

Chain both: dedupe first to remove noise, then sort for presentation.

Dedupe both sides before diff when comparing set membership ignoring multiplicity — multiset diffs need duplicate counts preserved intentionally.

Document whether policy is set equality or bag equality before deduping prior to compare.

Trim trailing spaces on each line when exports add invisible padding — or duplicates persist annoyingly.

Lowercase via case-converter before dedupe when case-insensitive uniqueness is required.

Typos like colour versus color remain two lines — manual review or edit-distance algorithms needed for fuzzy collapse.

Semantic duplicate URLs with different query strings stay distinct — normalize URLs with url-encoder-decoder rules separately.