diff --git a/readme.md b/readme.md
index e78b959..6530d66 100644
--- a/readme.md
+++ b/readme.md
@@ -8,7 +8,7 @@ GPT Copy is a command-line tool that recursively scans a directory, collects rea
 - **Structured Output:** Concatenates file contents into a structured markdown document with file-specific code fences.
 - **File Filtering:** Supports glob-style include (`-i/--include`) and exclude (`-e/--exclude`) patterns for precise file selection.
 - **Force Mode:** The `-f/--force` option bypasses ignore rules and Git-tracked file restrictions.
-- **Line Numbering:** Add zero-padded line numbers to each file's content using the `-n/--number` option (similar to `cat -n`).
+- **Line Numbering:** Zero-padded line numbers are added to each file's content by default (similar to `cat -n`). Use `--no-number` to disable.
 - **Token Counting:** Includes a separate `tokens` CLI command to count the number of tokens in text using OpenAI’s `tiktoken` library with GPT-4o model encoding.
 
 ## Installation
@@ -76,12 +76,17 @@ Ignore `.gitignore` and Git-tracked file restrictions to process **all** files:
 gpt-copy /path/to/directory -f
 ```
 
-### Add Line Numbers (`-n` or `--number`)
-Enable line numbering for the content of each file. This option prefixes each line with a zero-padded line number, similar to the Unix `cat -n` command.
+### Line Numbers (enabled by default)
+Line numbering is **enabled by default** for the content of each file. Each line is prefixed with a zero-padded line number, similar to the Unix `cat -n` command.
 
-**Usage Example:**
+**Basic usage (line numbers included):**
 ```sh
-gpt-copy /path/to/directory -n
+gpt-copy /path/to/directory
+```
+
+**Disable line numbers:**
+```sh
+gpt-copy /path/to/directory --no-number
 ```
 
 ### Count Tokens with `tokens`
@@ -107,7 +112,7 @@ Count the number of tokens in a given text using GPT-4o encoding. The command re
 3. **Reads and Formats Files:**
    - Detects file type based on extension.
    - Wraps file contents in appropriate markdown code fences.
-   - Adds line numbers if the `-n/--number` option is enabled.
+   - Adds line numbers by default (can be disabled with `--no-number`).
    - Skips binary or unrecognized file types.
 
 4. **Applies File Filtering:**
diff --git a/src/gpt_copy/gpt_copy.py b/src/gpt_copy/gpt_copy.py
index a28f751..1deca8b 100755
--- a/src/gpt_copy/gpt_copy.py
+++ b/src/gpt_copy/gpt_copy.py
@@ -500,11 +500,11 @@ def write_output(
     help="Glob pattern(s) to exclude files (e.g., 'src/tests/*')",
 )
 @click.option(
-    "-n",
-    "--number",
-    "line_numbers",
+    "--no-number",
+    "no_line_numbers",
     is_flag=True,
-    help="Add line numbers to file content.",
+    default=False,
+    help="Disable line numbers for file content.",
 )
 def main(
     root_path: Path,
@@ -512,7 +512,7 @@ def main(
     force: bool,
     include_patterns: tuple[str, ...],
     exclude_patterns: tuple[str, ...],
-    line_numbers: bool,
+    no_line_numbers: bool,
 ) -> None:
     """
     Main function to start the script.
@@ -523,8 +523,9 @@ def main(
         force (bool): If True, ignore .gitignore and Git-tracked files.
         include_patterns (Tuple[str, ...]): The tuple of include glob patterns.
         exclude_patterns (Tuple[str, ...]): The tuple of exclude glob patterns.
-        line_numbers (bool): If True, add line numbers to the file contents.
+        no_line_numbers (bool): If True, disable line numbers.
     """
+    
     root_path = root_path.resolve()
     print(f"Starting script for directory: {root_path}", file=sys.stderr)
     gitignore_specs, tracked_files = get_ignore_settings(root_path, force)
@@ -538,7 +539,7 @@ def main(
         tracked_files,
         include_patterns=list(include_patterns),
         exclude_patterns=list(exclude_patterns),
-        line_numbers=line_numbers,
+        line_numbers=not no_line_numbers,
     )
 
     if output_file:
diff --git a/test.txt b/test.txt
new file mode 100644
index 0000000..d670460
--- /dev/null
+++ b/test.txt
@@ -0,0 +1 @@
+test content
diff --git a/tests/test_line_numbers_default.py b/tests/test_line_numbers_default.py
new file mode 100644
index 0000000..7e7835a
--- /dev/null
+++ b/tests/test_line_numbers_default.py
@@ -0,0 +1,42 @@
+"""Test that line numbers are enabled by default."""
+
+from pathlib import Path
+
+from click.testing import CliRunner
+from gpt_copy.gpt_copy import main
+
+
+def test_line_numbers_enabled_by_default(tmp_path: Path):
+    """Test that line numbers are enabled by default without -n flag."""
+    # Create a test file with multiple lines
+    test_file = tmp_path / "test.txt"
+    test_file.write_text("line one\nline two\nline three\n", encoding="utf-8")
+
+    runner = CliRunner()
+    result = runner.invoke(main, [tmp_path.as_posix()])
+    
+    assert result.exit_code == 0
+    # Check that line numbers are present in the output
+    assert "1: line one" in result.output
+    assert "2: line two" in result.output
+    assert "3: line three" in result.output
+
+
+def test_no_number_flag_disables_line_numbers(tmp_path: Path):
+    """Test that --no-number flag disables line numbers."""
+    # Create a test file with multiple lines
+    test_file = tmp_path / "test.txt"
+    test_file.write_text("line one\nline two\nline three\n", encoding="utf-8")
+
+    runner = CliRunner()
+    result = runner.invoke(main, [tmp_path.as_posix(), "--no-number"])
+    
+    assert result.exit_code == 0
+    # Check that line numbers are NOT present in the output
+    assert "1: line one" not in result.output
+    assert "2: line two" not in result.output
+    assert "3: line three" not in result.output
+    # But the content should still be there
+    assert "line one" in result.output
+    assert "line two" in result.output
+    assert "line three" in result.output
\ No newline at end of file