Web Hex Editor & File Compare

Editing a File in Hex or ASCII

The editor displays every byte in two synchronized forms. The center columns show hexadecimal values, and the right column shows printable ASCII characters. Editing either view changes the same underlying byte.

1. Open or create a file

Select Open File and choose a file from your computer.
The file is processed locally in your browser; it is not uploaded.
To start with a blank file, select New Empty, then use Insert Byte.

2. Understand the display

OFFSET identifies the byte position at the start of each row.
Use the Offset selector on the toolbar to display offsets in hexadecimal or decimal.
Columns 00 through 0F contain 16 hexadecimal bytes per row.
The ASCII area shows printable characters. A dot represents a non-printable byte.
The Selected Byte panel shows the chosen byte in hexadecimal, decimal, ASCII, and binary.

3. Edit hexadecimal bytes

Click a byte in the hexadecimal area.
Type two hexadecimal digits, such as 41, 00, or FF.
After the second digit, the byte is changed and selection advances to the next byte.
You may also double-click a byte and enter the value in the Edit Hex Byte window.

4. Edit ASCII characters

Click a character in the ASCII area.
Type one character. For example, typing A writes hexadecimal 41.
Selection automatically advances to the next byte.
Double-click a character to edit it in a separate window.

5. Insert, delete, search, and navigate

Insert Byte inserts a new 00 byte before the selected position.
Delete Byte removes the selected byte and shifts later bytes left.
Use the Offset box and select Go. A value without a prefix follows the selected format: 220 means hexadecimal 0x220 in Hexadecimal mode and decimal 220 in Decimal mode. Explicit 0x100, 100h, and 256d notation can override the selected format.
Use the Search selector to choose Hex or ASCII. Hex mode accepts byte pairs such as 50 4B 03 04; ASCII mode searches the exact text string you type. Select Find again for the next match.
Undo and Redo reverse or restore edits.

6. Save the edited file

Select Save File.
The editor prepares a new download containing the current byte data.
Your original disk file is not overwritten automatically; the browser downloads a new copy.

Important: Changing bytes can make a program, image, archive, database, or document unusable. Keep an untouched backup of important files.

Comparing Two Files

The comparison feature checks the main file against a second file byte by byte. It reports whether the files are identical, how many byte positions differ, their size difference, and the first differing offset.

1. Load the two files

Select Open File to load the main file.
Select Open Compare File to load the second file.
Wait for the comparison progress to finish. Large files may require additional time.

2. Read the comparison summary

Files are identical means both files have the same size and every byte matches.
Different byte positions is the total count of mismatched positions, including bytes that exist only in the longer file.
First difference gives the earliest mismatching offset.
Size difference shows how many more or fewer bytes the main file contains.

3. Inspect differences

Differing bytes are highlighted in the editor.
The Difference List displays the first 250 mismatching offsets to keep memory usage reasonable.
Select an item in the list to jump to that offset in the main file.
Each list entry uses the form main byte → compare byte. A value of -- means that file has no byte at that position.

4. Edit while comparing

You may edit the main file while the comparison file remains loaded. Difference highlighting and the summary update as changes are made. This is useful for manually making the main file match the comparison file.

5. Finish or start another comparison

Select Clear Compare to remove only the second file and keep the main file open.
Select Reset to clear both files, all edits, search state, and comparison results.

Performance note: The editor counts all differences but lists only the first 250. Visible differences are calculated directly from the loaded file buffers, allowing large comparisons without storing every mismatch in memory.

Keyboard Shortcuts and Useful Tips

Key	Action
Arrow keys	Move between bytes.
Tab	Switch the selected editing mode between Hex and ASCII.
Insert	Insert a zero byte before the selected byte.
Delete	Delete the selected byte.
Ctrl+Z	Undo the most recent edit.
Ctrl+Y	Redo an undone edit.
Ctrl+S	Save the current file through the browser download system.
Ctrl+F	Move focus to the search box.
Esc	Close the tutorial or byte-edit window.

Tips

Hexadecimal digits are 0–9 and A–F.
One byte ranges from hexadecimal 00 to FF, or decimal 0 to 255.
Modified bytes are highlighted separately from comparison differences.
The editor renders only visible rows, so scrolling remains responsive with large files.
Use Reset when you need a completely fresh workspace.

Edit Byte