Free Online Duplicate Line Remover - Deduplicate Text Lists Instantly
The Delimiter.site Dedupe Lines tool removes duplicate lines from any list in real time. Paste your text, and the tool immediately separates unique lines into one panel and removed duplicates into another - so you can see exactly what was removed and copy each result independently.
How Deduplication Works
Each line in your input is compared against every line seen before it. The first occurrence of any line is kept in the Unique Lines output. Every subsequent occurrence of the same line is moved to the Removed Duplicates output. The original order of unique lines is preserved. If you also need the list sorted, run it through the line sorter afterwards.
Case-Insensitive Mode
When Case-insensitive is enabled, lines are compared without regard to capitalisation. Apple, apple, and APPLE are treated as the same line, and only the first occurrence is kept. This is essential when deduplicating data collected from different sources where casing may be inconsistent.
Trim Lines
When Trim lines is enabled (it is on by default), leading and trailing whitespace is stripped from each line before comparison. A line with a trailing space is treated the same as the identical line without it - which is almost always the correct behaviour for real-world data.
The Two Output Panels
Unique Lines
The top-right panel shows every line that appeared exactly once, or the first occurrence of any line that appeared multiple times. This is your clean, deduplicated list.
Removed Duplicates
The bottom-right panel shows every line that was removed - the second, third, and subsequent occurrences of any duplicated value. This panel is highlighted in red so it is immediately obvious which lines were discarded. You can copy the removed lines separately to audit what was stripped.
How to Use the Dedupe Lines Tool
Step 1 - Paste Your List
Click Paste to pull text from your clipboard, or type directly into the input panel. The deduplication runs automatically on every change - there is no convert button to press.
Step 2 - Set Your Options
Toggle Case-insensitive and Trim lines in the control bar at the top. The output panels update immediately when you change either option.
Step 3 - Copy Your Results
Click the copy icon in the Unique Lines panel header to copy your clean list. Click the copy icon in the Removed Duplicates panel to copy the discarded lines for auditing. The item count in the bottom bar shows how many duplicates were removed.
Common Use Cases
Cleaning Email and Contact Lists
Marketing lists collected from multiple sources often contain duplicate email addresses. Paste the combined list, enable Case-insensitive, and copy the unique lines to get a clean list ready for your email platform.
Deduplicating SQL Query Results
When a query returns rows without a DISTINCT clause, you may get duplicates.
Copy the result column, paste it here, and deduplicate faster than rewriting the query.
Preparing Import Files
CRMs, e-commerce platforms, and databases reject imports with duplicate primary keys. Deduplicate your CSV or list before importing to avoid validation errors and failed uploads.
Auditing What Was Removed
Unlike most dedupe tools that silently discard duplicates, the removed-duplicates panel shows you exactly what was stripped. Copy it to a separate document if you need a record of every duplicate that was found.