How to open a HEX file on Android: applications, instructions and nuances

Files with the extension .hex (or simply “hex files”) are binary data in hexadecimal format, which are often used for flashing microcontrollers, storing memory dumps, or low-level device settings. On a PC, they are opened with specialized editors like HxD or Hex Workshop, but what to do if the file is on a smartphone and there is no computer at hand?

In this article you will find 5 working methods open HEX on Android - from simple viewers to advanced editing tools. We will look at which applications support hexadecimal format, how to avoid errors when working with binary data, and what to do if the file does not open. Important: not all HEX files are intended for viewing on mobile devices - some may contain firmware for specific equipment (for example, Arduino or ESP32), and changing them without knowing the structure will lead to the device not working.

If you just need to view the contents, lightweight ones will do viewers. If editing or analysis of the structure is required, more powerful tools will be required. Let's start with the simplest.

1. What is a HEX file and why open it on Android

HEX file (from English hexadecimal —“hexadecimal”) is a text or binary file containing data in a format convenient for reading by microcontrollers. Most often, such files are found in three scenarios:

• 🔧 Firmware for microcontrollers (Arduino, STM32, ESP8266, etc.). Contain machine code that is loaded into the device memory.
• 💾 Memory dumps. Copies of the contents of flash memory, RAM, or other storage devices created for analysis or recovery.
• 🔍 Low-level configurations. For example, files with BIOS settings, bootloaders or specialized software.

On Android, you may need to open HEX files to:

• 📱 View the contents of the firmware before downloading to the device (for example, to make sure that the file is not damaged).
• 🔄 Editing individual bytes in a memory dump (if you know what you're doing!).
• 🛠️ Diagnosing errors in the operation of microcontrollers (for example, comparing the original and modified HEX).

⚠️ Attention: Do not edit HEX firmware filesif you are not sure their structure. An error in even one byte can render the device inoperable. For example, firmware for Arduino Nano is not suitable for ESP32, even if the files have the same extension.

If the file got onto your phone by accident (for example, through a messenger or email), first clarify its purpose. It may be intended to be downloaded onto a PC or specialized equipment.

2. TOP 3 applications for viewing HEX on Android

For basic viewing of the contents of HEX files, light applications from Google Playare suitable. They do not require root access and work on most devices. Here are the proven options:

Application	Editing support	Max. file size	Add. functions
Hex Editor (from DevCom)	❌ No	100 MB	Search by hexadecimal values, export to TXT
Hex Viewer (from Simple Mobile Tools)	✅ Yes (basic)	500 MB	Byte highlighting, support for large files
Binary Eye	✅ Yes (advanced)	1 GB	Structure analysis, file comparison, plugin support

Let's look at each in more detail.

2.1. Hex Editor (DevCom) - a simple viewer

This application is suitable for quick view small HEX files (up to 100 MB). The interface is minimalistic: hexadecimal values are displayed on the left, their text representation is displayed on the right. (if possible).

How to use:

1. Install the application from Google Play.
2. Open it and select the file through the built-in file manager.
3. Scroll the contents up and down, use search (Ctrl+F on the connected keyboard).

⚠️ Attention: The application does not save changes. data-i="91">Advantages: is read-only. If you need to edit the file, use Hex Viewer or Binary Eye.

Advantages:

• 🚀 Fast loading even on weak devices.
• 📱 Does not require additional permissions.
• 🆓 Free version without unnecessary water.

2.2. (Simple Mobile Tools) - basic editing

This tool allows you not only to view, but also make changes to HEX files. Files up to 500 MB are supported, there is a function for searching and replacing bytes.

Instructions for editing:

1. Open the file in the application.
2. Click on any byte - an editing window will appear.
3. Enter a new hexadecimal value (for example, replace FF by 00).
4. Save changes through the menu (File → Save).

Limitations:

• 🔄 There is no undo function (Undo) - all changes are applied immediately.
• 📱 On weak devices it may slow down when working with files >200 MB.

2.3. Binary Eye - advanced analysis

The most functional application on the list. Supports:

• 🔍 File comparison (useful for finding differences between versions. firmware).
• 📊 Structure analysis (for example, searching for headers or signatures).
• 🔧 Support plugins for working with specific formats (for example, Intel HEX).

How to compare two HEX files:

1. Open the first file in Binary Eye.
2. Click Tools → Compare Files.
3. Select the second file.
4. The application will show the differences in bytes (highlighted color).

⚠️ Attention: To work with files >1 GB you will need a device with 4+ GB of RAM. On weak smartphones the application may close with an error Out of Memory.

3. How to open a HEX file without applications (via Total Commander)

If you do not want to install specialized apps, you can use a file manager Total Commander with a plugin for viewing binary files. This method is suitable. for quick view without editing.

Instructions:

1. Install Total Commander from Google Play.
2. Download the plugin Hex Viewer Plugin (available in the plugins section inside the application).
3. Find your HEX file in the file manager.
4. Select it and select it in the menu Open with → Hex Viewer.

Advantages of the method:

• 📁 No need to install a separate application.
• 🔍 You can quickly switch between text and hexadecimal modes.

Disadvantages:

• ❌ It is not possible to edit the file.
• ⚠️ The plugin may display files >50 incorrectly MB.

Download Total Commander|Install the Hex Viewer plugin|Find the file in the device memory|Open via the context menu-->

4. Editing HEX via Termux (for advanced users)

If you need deep editing HEX files with support for scripts or automation, you can use Termux a Linux terminal emulator for Android. This method requires knowledge of the command line, but gives maximum flexibility.

Steps for installation and configuration:

1. Install Termux from Google Play or from official website (F-Droid).
2. Update the packages:

   pkg update && pkg upgrade

3. Install a hex editor xxd or hexedit:

   pkg install xxd

4. Copy the HEX file to the folder /sdcard (internal memory) or /storage/emulated/0.
5. Open the file for viewing:

   xxd /sdcard/Download/yourfile.hex

For editing, use hexedit:

1. Install it:

   pkg install hexedit

2. Open the file:

   hexedit /sdcard/Download/yourfile.hex

3. Use the arrow keys to navigate, Tab to switch between hexadecimal and text modes.
4. Save changes: Ctrl+X → Y → Enter.

Warnings:

• 🔐 Termux does not have access to the root file system without root access.
• 📱 On some devices (for example Xiaomi or Huawei) work with files in external memory may be blocked.

How to fix the "Permission denied" error in Termux?

If you see an error when trying to open a file Permission denied, do:

1. Go to settings Termux (~/.termux/termux.properties).
2. Add line allow-external-apps=true.
3. Restart Termux and try again. If this does not help, copy the file to the folder /data/data/com.termux/files/home via Explorer with root access.

5. Online services for viewing HEX (without installation)

If you do not want to install applications, you can use online tools. They work directly in the browser, but have restrictions on file size and confidentiality.

Popular services:

• 🌐 HexEd.it —supports files up to 50 MB, editing is available.
• 🌐 HexEditor Online —simple viewer without registration.
• 🌐 CyberChef —not only HEX, but also other formats (BASE64, XOR, etc.).

How to use HexEd.it:

1. Open the site in a browser (recommended Chrome or Firefox).
2. Click Open File and download the HEX file from the device.
3. Use the toolbar to navigate, search or edit.
4. Download the modified file via File → Download.

⚠️ Attention: Do not download confidential HEX files. online services. They may store data on their servers, for example, firmware with unique device identifiers or memory dumps with personal information.

Pros of the online method:

• 📱 No need to install anything.
• 🔄 You can work from any device (even an iPhone or PC).

Cons:

• 🚫 Limitation file size (usually up to 100 MB).
• 🔒 Risk of data leakage (if the service does not encrypt downloads).

6. Common errors and how to fix them

When working with HEX files on Android, users often encounter problems. Here are the most common errors and their solutions:

Error	Cause	Solution
File cannot be opened or Unsupported format	The file is damaged or has a non-standard structure.	Check the integrity of the file (for example, through a hash) or try another application.
Out of Memory when opening a large file	Not there is enough RAM.	Close other applications or use the PC to work with files >1 GB.
The application closes when saving	No permission to write to the folder.	Save the file to internal memory or use Termux.
Russian characters are not displayed	Incorrect encoding.	Try changing the encoding in the application settings (for example, to UTF-8 or Windows-1251).

If the file does not open in any application:

1. Check the extension - perhaps it is not HEX, but another format (for example, .bin or .dat).
2. Make sure that the file is not archived (try renaming to .zip and open).
3. If the file was downloaded from the Internet, check its hash sum (for example, via Hash Droid).

7. Security: how not to damage data when working with HEX

HEX files often contain critical information - firmware, memory dumps or configurations. An editing error can lead to:

• 💥 Data loss (if this is a memory dump).
• 🔌 Device failure (if this is microcontroller firmware).
• 🔒 Security compromises (if a file contains encryption keys).

Rules for safe operation:

1. Always make a backup copy original file.
2. Use tested applications (from this manual).
3. If you edit the firmware - examine its structure (usually described in the device datasheet).
4. Do not open HEX files from unverified sources —they may contain malicious code.

Safe editing example:

Suppose you have firmware for Arduino Uno v format Intel HEX. Before changing:

1. Check that the file matches the model (there should be a header at the beginning :020000040000FA or similar).
2. Open it in Binary Eye and compare with the original firmware.
3. Make changes only to those bytes that are specified in the documentation.
4. Save under a new name (for example, firmware_mod.hex).

FAQ: Answers to frequently asked questions

Is it possible to open a HEX firmware file for Arduino on Android?

Yes, but only for viewing or minor edits. To fully work with firmware, it is better to use a PC and Arduino IDE. On Android you can:

• View content in Hex Viewer.
• Compare two firmware versions in Binary Eye.
• Edit individual bytes (if you know their purpose).

To download firmware to Arduino from your phone you will need an OTG cable and a specialized application (eg ArduinoDroid).

Why does a HEX file appear as a bunch of random characters?

This is normal - HEX files contain binary data that does not always have a textual representation. What you see on the right in the hex editor is an attempt to display bytes as characters. For example:

• Byte 48 will be displayed as H.
• Byte 00 —as an empty character.
• Byte FF —as ÿ (if encoding is used Windows-1251).

What is important for analysis is left columns (hexadecimal values), not the text representation.

How to convert HEX to readable text?

If you are sure that the HEX file contains encoded text (for example, a configuration in the format UTF-8), you can try:

1. Open the file in Hex Viewer.
2. Find areas with printable characters (letters, numbers).
3. Copy hexadecimal values and decode them via CyberChef (option From Hex).

If the text is not readable, perhaps a different encoding is used or the data is encrypted.

Is it possible to open a 2 GB HEX file on Android?

Technically yes, but with caveats:

• 📱 You will need a device with 4+ GB of RAM (for example, Samsung Galaxy S22 or OnePlus 10 Pro).
• 🔧 Use Binary Eye or Termux with the utility xxd.
• ⚠️ Split the file into parts (for example, through split in Termux) if the application does not cope.

On weak devices (for example, Redmi 9A) such files will not open - the system will kill the process due to lack of memory.

How to find out what device a HEX file is intended for?

You can determine the purpose of a HEX file by:

• 📄 File name (for example, arduino_nano.hex or esp32_firmware.hex).
• 🔍 Signature (first bytes). For example:
  • :02000004 — firmware in format Intel HEX.
  • 7F 45 4C 46 — ELF file (executable file for Linux).
• 📋 Documentation to the device (look for the section Firmware Format).

If you are not sure - do not edit the file. Contact the device manufacturer or community (for example, on the forum Arduino or ESP32).