Getting Started with HexTool: A Beginner’s GuideHexTool is a powerful hex editor designed to make inspecting, editing, and analyzing binary files straightforward for developers, reverse engineers, and hobbyists. This guide walks you through what HexTool is, why you might use it, how to install and configure it, basic and intermediate workflows, and practical tips to avoid common pitfalls.
What is HexTool?
HexTool is a hex editor that displays the raw bytes of files in hexadecimal alongside an ASCII (or other encoding) representation, allowing you to view and edit data at the byte level. Unlike text editors, hex editors operate directly on binary data, making them essential for tasks like:
- Fixing corrupted files
- Patching executables
- Analyzing file formats and network captures
- Reverse engineering and forensic investigations
- Low-level debugging and firmware editing
Key fact: Hex editors show data in hexadecimal (base-16) and often provide an ASCII view for readable characters.
When to use HexTool
Use HexTool when you need precise control over bytes or when higher-level tools can’t access the underlying binary structure. Typical scenarios:
- Editing headers (e.g., PNG, PDF) to repair or alter metadata
- Searching for magic numbers or signatures to identify file types
- Modifying save files or game assets
- Learning file format internals by inspecting raw layouts
- Patching small parts of executables or firmware images
Installing HexTool
HexTool is available for Windows, macOS, and Linux. Installation methods vary:
- Windows: Download installer (EXE) and run it. Optionally use portable ZIP.
- macOS: Use Homebrew: brew install hextool (if available) or download from the website.
- Linux: Install via your distribution’s package manager (apt, dnf) or download a static binary.
After installation, launch HexTool from your Applications menu or via command line: hextool filename.bin
First-time setup and configuration
When you first open HexTool, configure these basics for a smoother experience:
- Encoding/view mode: Choose ASCII, UTF-8, UTF-16, or other encodings for the text pane.
- Bytes per row: Common choices are 16 or 8; 16 is standard and fits well with 4- or 8-byte word views.
- Highlighting rules: Enable or create patterns to highlight magic numbers, checksums, or important offsets.
- Backup settings: Enable automatic backups or a safety copy to avoid accidental data loss.
- Plugins/extensions: Install available plugins for file format inspectors, checksums, or scripting.
Core features you’ll use immediately
- Hex view and ASCII pane: Main interface showing offsets, hex bytes, and text.
- Search and replace: Search by bytes (hex), text strings, or regex; replace single bytes or sequences.
- Go to offset: Jump directly to a specific byte offset or relative position.
- Data interpretation: View selected bytes as integers (signed/unsigned), floats, pointers, or timestamps.
- Bookmarks/annotations: Mark and comment important offsets to keep track of structure.
- Undo/redo: Essential for safely testing edits—ensure it’s enabled.
- Checksums and hashing: Compute CRC, MD5, SHA1 for selected ranges or whole file.
- Scripting support: Automate repetitive tasks with built-in scripting (often Python or Lua).
Basic workflows
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Inspecting a file
- Open file in HexTool.
- Scan the first few bytes for a magic number (e.g., PNG: 89 50 4E 47).
- Note offsets for headers and metadata in the ASCII pane.
-
Searching for strings
- Use text or hex search to find readable strings (e.g., URLs, version strings).
- Translate found offsets to structure fields (counts, lengths) you recognize.
-
Editing a value
- Backup the file.
- Go to the offset you want to change.
- Switch to overwrite mode (if available) and edit the bytes.
- Verify dependent checksum fields and update if needed.
- Save and test the modified file in the target application.
-
Patching an executable (simple example)
- Identify the instruction bytes to change.
- Replace opcodes carefully; maintain instruction length or apply a jump stub.
- Recalculate checksums/signatures if required by the loader.
- Test in a controlled environment.
Intermediate techniques
- Template parsing: Use or create templates that map file structures (fields, types, offsets) into a readable form.
- Data carving: Extract embedded files by finding signatures and saving ranges as separate files.
- Endianness handling: Be mindful of little vs. big endian when interpreting multi-byte values.
- Pointer chasing: Follow pointer values reading addresses and jumping to referenced offsets.
- Binary diffing: Compare two binaries to find changes—use HexTool’s diff or an external binary diff tool.
- Automated patching: Write a script to apply a repeatable patch across multiple files or firmware images.
Common pitfalls and how to avoid them
- No backups: Always keep an unmodified copy before editing.
- Misinterpreting endianness: Check specifications or test small values (e.g., 0x0100).
- Overwriting structure lengths: When inserting bytes, understand whether the format supports in-place insertion or fixed offsets.
- Missing checksums/signatures: Many formats and executables include integrity checks—update them if you change data.
- Permissions and firmware safety: Don’t flash firmware unless you’re sure; use emulation or recovery methods when possible.
Helpful tips & shortcuts
- Use bookmarks to quickly navigate complex files.
- Learn common magic numbers (PNG, ZIP, ELF, PE, PDF) to identify embedded content.
- Combine HexTool with higher-level tools: file format docs, disassemblers (e.g., Ghidra), and network analyzers (Wireshark).
- When scripting, make idempotent changes so scripts can run safely multiple times.
- For collaborative work, record edits as patches (diffs) rather than distributing altered binaries.
Example: quick repair of a corrupted PNG header
- Open the PNG file and verify the first eight bytes: 89 50 4E 47 0D 0A 1A 0A.
- If bytes differ, replace them with the correct sequence.
- Check the IHDR chunk length and CRC—recompute CRC for IHDR if needed.
- Save a copy and open the image in a viewer.
Learning resources
- File format specifications (PNG, ZIP, ELF, PE)
- HexTool documentation and built-in templates
- Reverse engineering courses and communities
- Open-source example projects and hex editing walkthroughs
Final notes
HexTool puts byte-level control in your hands. Start with safe, reversible edits, learn to read common file structures, and combine HexTool with complementary tools (disassemblers, format docs) as your confidence grows. With practice, you’ll move from simple fixes to advanced analysis and automated workflows.
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