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How to Underline or Bold Text Using ANSI Codes in Batch Script

For years, Batch programmers were limited to plain text output. If you wanted to emphasize a word, your only option was to use ALL CAPS or surround it with symbols like ***IMPORTANT***. However, modern Windows terminals (Windows Terminal and updated ConHost on Windows 10/11) now support ANSI Escape Codes, allowing you to apply professional formatting like Bold, Underline, and even Italics directly in your scripts.

In this guide, we will demonstrate how to enable and use these formatting codes to enhance your text output.

Essential ANSI Formatting Codes​

To apply formatting, you use a specific code sequence followed by the text you want to format, and you must end the formatted section with the "Reset" code to return to normal.

EffectANSI CodeNotes
Reset AllESC[0mClears all formatting and colors
Bold / BrightESC[1mMay display as brighter color rather than bold, depending on the terminal
DimESC[2mNot supported in all terminals
UnderlineESC[4mWidely supported
Invert (Negative)ESC[7mSwaps foreground and background colors
info

Note on Bold vs. Bright: The ESC[1m code is defined as "Bold" in the ANSI standard, but many Windows console implementations render it as a brighter foreground color rather than a heavier font weight. Windows Terminal supports true bold rendering if the configured font has a bold variant. The legacy ConHost typically renders it as bright intensity only.

Setup: Capturing the Escape Character​

To use these codes in Batch, you need the literal Escape character (ASCII 27). We store this in a variable to make our script readable.

@echo off
setlocal EnableDelayedExpansion

:: Get real ESC character from PowerShell
for /f %%A in ('powershell -NoProfile -Command "[char]27"') do set "ESC=%%A"

:: Define ANSI styles
set "RESET=!ESC![0m"
set "BOLD=!ESC![1m"
set "UNDERLINE=!ESC![4m"
set "REVERSE=!ESC![7m"

echo This is regular text.
echo !BOLD!This is Bold text.!RESET!
echo !UNDERLINE!This is Underlined text.!RESET!
echo !BOLD!!UNDERLINE!This is Bold AND Underlined text.!RESET!
echo !REVERSE!Highly Important Warning!RESET!

endlocal
pause

Combinations and Nesting​

A powerful feature of ANSI codes is that you can combine effects. For example, if you want a bold, underlined, red warning:

set "RED=!ESC![91m"
echo !BOLD!!UNDERLINE!!RED!CRITICAL ERROR DETECTED!RESET!

You can also combine multiple codes into a single escape sequence by separating them with semicolons, which is more concise:

:: Bold (1) + Underline (4) + Bright Red (91) in a single sequence
echo !ESC![1;4;91mCRITICAL ERROR DETECTED!RESET!

Formatting Specific Words in a Sentence​

You don't have to format the whole line. You can toggle the formatting on and off for specific words.

echo The status of the server is !BOLD!ONLINE!RESET! and !UNDERLINE!stabilized!RESET!.

Why Use ANSI Bold and Underline?​

1. Visual Hierarchy​

In a long log output, bolding the timestamps or the service names makes it much faster for a human eye to scan and find specific entries.

2. Error Highlighting​

Bolding the word ERROR or FATAL ensures that the user doesn't miss the most critical information amidst a sea of standard text.

3. Professionalism​

Underlined headers make your script look like a modern CLI application (like git or kubectl) rather than a legacy 1990s batch file.

Troubleshooting: Why does my text show ←[1m?​

If your terminal displays the raw codes (like ←[1m) instead of bolding the text, it means:

  1. Old Windows: You are on Windows 7 or 8, which do not natively support ANSI in the terminal.
  2. ANSI Not Enabled: You might need to enable the "Virtual Terminal" feature in the registry for older Windows 10 builds.

The Fix: You can enable ANSI support by running this command once in an elevated command prompt:

reg add HKCU\Console /v VirtualTerminalLevel /t REG_DWORD /d 1 /f

A new terminal session is required after setting this value for the change to take effect.

Summary​

The ability to Bold and Underline text via ANSI codes is a game-changer for Batch scripting. It moves your output from a monotone block of text to a structured, professional interface. By defining clear variables for !BOLD! and !RESET!, you can make your scripts significantly more communicative and easier for users to navigate.

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