unreliable.io

Keep only duplicate lines

How does it work?

This tool keeps only the duplicate lines from your text, removing any lines that appear only once. You can choose whether the comparison should be case-sensitive or case-insensitive.

Example of keeping only duplicates

Original text

Line 1
Line 2
Line 3
Line 1
Line 4
line 1
Line 2
Line 5
Line 3

Case-sensitive (default)

Line 1
Line 2
Line 3
Line 1
Line 2
Line 3

Case-insensitive

Line 1
Line 2
Line 3
Line 1
line 1
Line 2
Line 3

This tool is useful for:

Finding repeated items in a list
Identifying duplicate entries in data
Analyzing text for repetitive content
Extracting common elements from multiple sources
Detecting potential data entry errors

Options:

Case sensitive comparison: When enabled, "Line" and "line" are treated as different lines. When disabled, they are considered the same line.

Note:

This tool preserves all occurrences of duplicate lines in their original order. If you want to remove duplicate lines instead of keeping only the duplicates, use the "Remove duplicates" tool.

Related Tools

Remove Duplicates - Remove duplicate lines from text
Group and Count - Group similar lines and count occurrences
Sort Text - Sort lines alphabetically
Grep - Filter lines matching a pattern
Inverted Grep - Filter out lines matching a pattern

All Tools

See all available tools

Text tools

Decode base64 text Base64 encode text Trim whitespaces Decode URL text URL encode text Change text to uppercase Change text to lowercase Count words, lines, paragraphs

Encode/Decode

Encode text to MD5 Hex Encode text to SHA-1 Hex Encode text to SHA-256 Hex Encode text to SHA-512 Hex Encode text to SHA3-256 Hex Encode text to SHA3-512 Hex Encode text as URL Decode URL text Encode text to Base64 Decode Base64 text Encode text to Hex Decode Hex text ISO Timestamp to Epoch Milliseconds Epoch Milliseconds to ISO Timestamp

Increment/Decrement

Increment all numbers Decrement all numbers Duplicate and increment numbers Duplicate and decrement numbers Create sequence Increment duplicate numbers

Sort

Reverse order of lines Shuffle lines Sort case-sensitive A-z Sort case-sensitive z-A Sort case-insensitive A-Z Sort case-insensitive Z-A Sort line length ascending Sort line length descending Sort hexadecimally Sort lines by subselection Sort tokens Shuffle Characters JSON sort Hierarchical sort

Align

Align carets/selections Format text to columns/table Align text to left Align text to center Align text to right

Filter/Remove/Trim

Grep Inverted Grep Group by Grep Trim Trim Leading Trim Trailing Replace whitespaces with space Remove all spaces Remove duplicates Keep only duplicate lines Group and Count Remove empty lines Remove consecutive empty lines Remove all newlines

Convert/Minify

Convert Between Char and Int Minify JSON Minify JavaScript Convert Between JSON and YAML

Other

Reverse Letters Swap Words Swap Characters/Selections/Lines/Tokens Wrap or shift quotes Swap between quotes Straighten/Educate quotes Switch file path separators Select All Occurrences For All Carets Extend Selection in Different Mode Multi Replace Duplicate and Multi Replace Paste - camelCased Paste - and Keep Selections Create Border