How to View a Binary File (BIN, DAT and Unknown Files)

What "Viewing" a Binary File Can Tell You

A binary file, such as a .bin firmware image, a .dat file from an app, or a download with no extension, is just a sequence of bytes. Looking at those bytes can answer practical questions:

• What type of file is it? Most formats start with a recognisable signature, covered in file signatures and magic numbers.
• Does it contain readable text? Names, version numbers, URLs and error messages are often embedded as plain strings.
• Is it damaged or empty? A file full of 00 bytes, or one that ends abruptly, tells you something went wrong.
• Did it change? Comparing two versions byte by byte shows exactly what differs.

What a viewer can't do is make sense of a proprietary format for you. You'll see the raw structure, not a rendered document.

View a Binary File With Built-In Commands

macOS and Linux: xxd

xxd firmware.bin | head -n 20

Each output line shows an offset, sixteen bytes in hex, and their ASCII representation. xxd comes with the Vim package, which is installed on most systems.

macOS and Linux: hexdump

hexdump -C firmware.bin | head -n 20

The -C flag gives the canonical layout: offset, hex bytes and an ASCII column between | bars.

Windows: Format-Hex

Format-Hex -Path .\firmware.bin | Select-Object -First 20

Format-Hex is built into PowerShell. On older Windows versions, certutil -dump file.bin also prints a hex dump.

Extract Readable Text With strings

strings -n 6 firmware.bin | less

strings prints runs of printable characters at least six characters long (the -n value). It's a quick way to spot version numbers, copyright notices or paths inside an executable. On Windows, Microsoft's Sysinternals suite includes a strings tool.

View a Binary File in Your Browser

If you'd rather not use the command line, you can open a binary file in an online viewer. It has several views of the same bytes:

• Hex: the classic layout with offsets, hex bytes and an ASCII column.
• ASCII: the bytes as characters, with non-printable bytes shown as dots.
• Binary: each byte as eight 0s and 1s, useful for bit flags.
• Strings: readable text runs pulled out of the file.
• File info: size, checksums and a signature check that suggests the file type when it recognises one.

You can search for text or hex byte sequences, jump to an offset, compare two files, and export a hex dump or the strings list. Files up to 64 MB are read and analysed in your browser, so the file isn't uploaded to a server.

Reading What You See

The first time you look at a hex dump it can look like noise. A few patterns help:

• The first 4 to 16 bytes usually identify the format. 89 50 4E 47 is a PNG; 50 4B 03 04 is a ZIP (which includes DOCX, XLSX and APK files).
• Long runs of 00 are padding or empty space.
• Readable text in the ASCII column often marks headers, metadata or embedded messages.
• Repeating patterns may be a table of fixed-size records.

How to read a hex dump walks through a real example line by line.

Common Binary File Types You Might Be Holding

If a file turns out to be a known format, open it with the right application. A DICOM scan, for instance, is easier to inspect in a DICOM viewer than as raw bytes.

Binary or Text?

Some files with odd extensions are actually text: logs, configuration files, CSV exports. If the ASCII column of a hex view reads like sentences with 0A bytes (line feeds) scattered through it, you're looking at text, and a text viewer will serve you better. Binary vs text files explains the difference. For very large text files, a large file viewer is the right tool.

Summary

A hex viewer is the universal way to look inside any file. Use xxd, hexdump or Format-Hex if you're comfortable in a terminal, or a browser-based viewer for hex, strings, search and file-type detection without installing anything.