Reverse Hex

Reverse Hex – Byte Order Swapper

Reverse the byte order of hexadecimal values to convert between little-endian and big-endian. Paste one hex value per line and each line is reversed two digits at a time: 12345678 becomes 78563412 and DEADBEEF becomes EFBEADDE. Spaces, colons, and 0x prefixes in the input are ignored.

What is endianness?

Endianness describes the order in which the bytes of a multi-byte number are stored in memory or sent over a network. Big-endian stores the most significant byte first, the way we write numbers on paper. Little-endian stores the least significant byte first. x86, x64, and most ARM systems are little-endian, while network protocols such as TCP/IP use big-endian ("network byte order"). The 32-bit number 0x12345678 is therefore stored as 78 56 34 12 on a typical PC.

When you need to reverse hex

• Reading memory dumps and hex editors – values from a little-endian machine appear "backwards".
• Bitcoin and blockchain work – transaction and block hashes are displayed in reversed byte order compared with their internal representation.
• Network and file formats – converting fields between network byte order and host order, or reading headers of BMP, WAV, and ZIP files, which are little-endian.
• Linux /proc files – /proc/net/tcp shows IPv4 addresses such as 0100007F, which reversed is 7F000001 = 127.0.0.1.

Reversal units

Byte reversal is the most common, but you can also reverse 16-bit words (swap 1234 5678 to 5678 1234, useful for word-swapped Modbus registers), 32-bit dwords, or individual nibbles to mirror the whole string character by character. If a value has an odd number of digits, a leading zero is added so bytes stay aligned.

Output options

Choose a separator (none, space, colon, or comma), add a 0x prefix, and force uppercase. To convert the reversed value to decimal afterwards, use Hex to Decimal; to turn it into an IP address, use Hex to IP.