Duplicate Line Remover
Strip duplicate lines from logs, email lists, and datasets locally inside a background Web Worker.
Local Workspace (duplicate-lines)
How to Use Duplicate Line Remover
- 1Paste your multiline list, CSV column, or server log into the Source Lines pane.
- 2Configure Filter Rules for Case-Sensitive matching, Trim Whitespace, Remove Empty Lines, and Sort Output order.
- 3Verify Original Lines, Unique Lines, and Duplicates Removed metrics, then copy or download the clean list as a .txt file.
Technical Specifications & Guardrails
- O(N) hash-set deduplication running inside a dedicated Web Worker (up to 25 MB)
- Normalizes both Windows (CRLF) and Unix (LF) line endings automatically
- Independent toggles for Case-Sensitive comparison, Trim Whitespace, and Remove Empty Lines
- Preserves original first-seen line order by default or sorts Alphabetical (A-Z) / Reverse (Z-A)
Practical Example: Cleaning Exported Newsletter Subscriber Lists
- Sample Input
- 15,000 exported email addresses containing mixed-case duplicates (User@Example.com vs user@example.com), trailing spaces, and blank rows.
- Verified Local Output
- Deduplicated case-insensitively with whitespace trimmed and sorted A-Z in under 40 milliseconds without uploading subscriber PII.
Operational Limits & Browser Guardrails
Supports plain-text lists up to 25 MB (approximately 250,000+ lines). Payloads larger than 100 KB are automatically processed off the main thread in text.worker.ts. When Case-Sensitive is unchecked, the first casing variant encountered in the input is retained.
Frequently Asked Questions
Does removing duplicate lines change the order of my original list?
By default, Keep Original Order preserves the exact sequence of first appearance. You can optionally switch Sort Output to Alphabetical (A to Z) or Reverse Alphabetical (Z to A).
How many lines can I deduplicate at once without freezing my browser?
Because deduplication offloads inputs above 100 KB to text.worker.ts using an O(N) Set lookup, lists up to 25 MB (250,000+ lines) complete without blocking the UI thread.
What happens when Trim Whitespace is enabled?
Leading and trailing spaces or tabs on each line are stripped before comparing keys, preventing 'item' and ' item ' from being treated as distinct lines.