Remove Duplicate Lines

Open Remove Duplicate Lines on Happytails.ai. This view has the same page content and links, with explicit tool capabilities. Read the processing notes before using a tool.

Tool capabilities

{
  "id": "remove-duplicate-lines",
  "category": "text-tools",
  "built": true,
  "requirements": "Case sensitivity, whitespace normalization and keep-first/last; preserve chosen line order.",
  "implementation": {
    "fields": [],
    "experience": {
      "automatic": true,
      "single": false,
      "inputMaxLength": 1000000,
      "inputMode": "text",
      "label": "Your text",
      "placeholder": "Hello world!",
      "help": "Change the input or settings to update your result. Results update as you type. Up to 1,000,000 characters.",
      "helpParts": [
        "Change the input or settings to update your result.",
        "Results update as you type.",
        "Up to 1,000,000 characters."
      ],
      "action": null
    },
    "mode": "automatic",
    "interactive": false
  },
  "execution": "POST /api/v1/tools/remove-duplicate-lines/run",
  "api": {
    "id": "remove-duplicate-lines",
    "name": "Remove duplicate lines",
    "category": "text-tools",
    "description": "Remove repeated lines while keeping their first occurrence.",
    "notes": "",
    "human_path": "/en/text-tools/remove-duplicate-lines/",
    "method": "POST",
    "endpoint": "/api/v1/tools/remove-duplicate-lines/run",
    "schema_url": "/api/v1/tools/remove-duplicate-lines",
    "input_schema": {
      "type": "object",
      "additionalProperties": false,
      "properties": {
        "input": {
          "type": "string",
          "maxLength": 1000000,
          "default": "",
          "description": "Plain text input. File tools use files instead unless otherwise documented."
        },
        "options": {
          "type": "object",
          "additionalProperties": false,
          "properties": {}
        }
      }
    },
    "output_schema": {
      "type": "object",
      "required": [
        "tool",
        "result"
      ],
      "properties": {
        "tool": {
          "type": "string"
        },
        "result": {
          "type": "object",
          "required": [
            "text",
            "files"
          ],
          "properties": {
            "text": {
              "type": [
                "string",
                "null"
              ]
            },
            "data": {
              "description": "Parsed JSON when the textual result is JSON."
            },
            "name": {
              "type": "string"
            },
            "mime": {
              "type": "string"
            },
            "files": {
              "type": "array",
              "items": {
                "type": "object",
                "required": [
                  "name",
                  "mime",
                  "bytes",
                  "base64"
                ],
                "properties": {
                  "name": {
                    "type": "string"
                  },
                  "mime": {
                    "type": "string"
                  },
                  "bytes": {
                    "type": "integer"
                  },
                  "base64": {
                    "type": "string",
                    "contentEncoding": "base64"
                  }
                }
              }
            }
          }
        }
      }
    },
    "processing": "Server; same transformation code as browser tools",
    "limits": {
      "request_bytes": 8388608,
      "input_characters": 1000000,
      "files_bytes": 5242880,
      "max_files": 0,
      "timeout_seconds": 12
    }
  },
  "agent_processing": "Server; same transformation code as browser tools",
  "browser_agent": {
    "supported": true,
    "name": "transform_current_tool",
    "discovery": "WebMCP on the human page in a supporting browser",
    "verification": "See audit/API-AUDIT.md; availability is not verification"
  }
}

Page guide

Keep each line once and clear out the repeats.

Runs on your device

How to use Remove duplicate lines

Enter your text in the input field.
The result updates as you type. Adjust the available settings if needed.
Review the result, then use Copy result or a download link when available.

One copy of each line

The first occurrence of each exact line is kept. Line order is preserved, and matching is case-sensitive. Blank lines are treated like any other line.

Exact matches only

“Apple” and “apple” are different. Clean up extra spaces first if those should not distinguish the lines.

What to expect

Remove repeated lines while keeping their first occurrence. Matching is case-sensitive and includes spaces. The original order is preserved; lines that differ only in capitalization remain separate.

Try a small example

A
B
A