Mastering HxD: How to Read and Edit Raw Hex Code At the lowest level, all computer data is just a stream of binary ones and zeros. However, reading endless rows of binary is practically impossible for humans. That is where hexadecimal (hex) notation and hex editors come in.
HxD is one of the most powerful, lightweight, and dependable freeware hex editors available for Windows. Whether you want to reverse-engineer a file format, patch a software bug, recover corrupted data, or modify game saves, mastering HxD is a fundamental superpower.
Here is a practical guide to reading and editing raw hex code like a pro. What is Hexadecimal Code?
Before opening HxD, it helps to understand what you are actually looking at.
Hexadecimal is a base-16 number system. It uses sixteen distinct symbols: 0–9 to represent values zero to nine, and A–F to represent values ten to fifteen. One byte of data consists of 8 bits.
In hex, one byte is perfectly represented by two characters (ranging from 00 to FF).
For example, the decimal number 10 is 0A in hex. The decimal number 255 is FF. Navigating the HxD Interface
When you drag and drop a file into HxD, the interface splits into three primary vertical columns:
The Offset Column (Left): This acts as the address book or coordinate system. It tells you exactly where you are in the file. If the offset says 00000010, you are looking at the 17th byte of the file.
The Hexadecimal Block (Middle): This is the raw data of the file, organized into neat columns (usually 16 bytes per row). Each pair of characters represents one byte.
The Text Decode Pane (Right): HxD attempts to translate the hex bytes into human-readable characters using a specific encoding (like ASCII or ANSI). If a byte corresponds to a printable letter, you will see it here. If it does not, you will see a simple dot (.). How to Read Raw Hex Data
Reading hex is about recognizing patterns. Different file types start with unique identifiers called file signatures or magic bytes.
Identify the File Type: Even if a file has no extension, the first few bytes tell the story. An executable file (.exe) almost always starts with the ASCII characters MZ (hex 4D 5A). A ZIP file starts with PK (hex 50 4B).
Follow the Cross-Hair: Click on any byte in the middle column. HxD will instantly highlight its corresponding character in the right text pane and display its exact position in the bottom status bar.
Watch the Data Inspector: On the right side of the screen, the Data Inspector dynamically translates the selected byte(s) into different formats simultaneously, showing you what the hex translates to as a 16-bit integer, a 32-bit integer, or a floating-point number. Editing Hex Code Safely
Editing raw hex is incredibly precise. A single incorrect byte can permanently corrupt a file. Always back up your original file before making edits. There are two primary modes of editing in HxD: 1. Overwrite Mode (Default)
When you click on a hex pair and type a new value, it replaces the existing data. The file size remains exactly the same. This is the safest method for modifying values like high scores in game saves or changing text strings. 2. Insert Mode
If you press the Insert key, typing new hex pairs will push the existing data forward, increasing the overall file size. Be highly cautious with this mode; altering a file’s structure or size often breaks internal pointers, causing the program or file to crash. Changing Text Strings
If you want to change a word inside a file, click into the right-hand text pane, highlight the text, and type your new text.
The Rule of Length: Your new text string must be the exact same length or shorter than the original.
Null Terminators: If your new text is shorter, fill the remaining leftover bytes with 00 (Null bytes) in the hex column to signal the end of the text string. Advanced HxD Techniques 1. RAM and Disk Editing HxD does not just edit saved files; it can open live data.
Go to Tools > Open Main Memory to inspect and edit the active RAM of running processes.
Go to Tools > Open Disk to inspect raw data on hard drives or USB sticks (useful for data recovery). Note: This requires Administrator privileges. 2. Finding and Replacing Data
Use Ctrl + F to search through huge files. HxD allows you to search by Text-string, Hex-values, Integer values, or Floating-point values. You can swap bytes globally using Ctrl + R. 3. Comparing Files
If you have two versions of the same file and want to see what changed, go to Analysis > File-compare > Compare. HxD will align both files side-by-side and highlight every single differing byte. This is incredibly useful for tracking down save-game variables. Wrapping Up
Mastering HxD takes the mystery out of computing. By learning to navigate offsets, decode text panes, and safely overwrite bytes, you gain ultimate control over the data on your machine. Start small—experiment on simple .txt files or old video game saves—and soon you will be diagnosing file corruption and reverse-engineering data structures with ease.
To help you get started with your specific project, tell me: What kind of file are you trying to read or edit?
What is your ultimate goal (e.g., fixing a corrupt file, modding a game, finding hidden text)?
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