Endianness is the order in which bytes of a multi-byte integer are stored. Little-endian places the least significant byte first (used by x86 and ARM); big-endian places the most significant byte first (network byte order, older RISC architectures).

What word sizes are supported?

2 bytes (16-bit), 4 bytes (32-bit), and 8 bytes (64-bit). The total input length must be a whole multiple of the selected word size.

Can I roundtrip swap a value?

Yes — swapping the same input twice returns the original byte order, which the tool's tests verify automatically.

Swap Endianness

8 bytes (2 words)

Word size

Input (hex)

Swapped output

04 03 02 01 08 07 06 05

Technical details

How the Swap Endianness Tool Works

What the Tool Does

The Swap Endianness tool reverses the byte order of a hexadecimal input within a configurable word size (2, 4, or 8 bytes). It is intended for converting between little-endian and big-endian representations of fixed-width integers stored as hex, which is a frequent need when working with binary file formats, network protocols, or low-level debugging tools that disagree on byte order.

Common Developer Use Cases

Reverse engineers normalize hex dumps from x86 or ARM (little-endian) and PowerPC or MIPS (historically big-endian) so they can compare values across architectures. Network engineers convert host-byte-order integers to network byte order (always big-endian) before embedding them in packet captures. Embedded developers debug structures stored in flash by realigning bytes to the format expected by their analysis tooling.

Data Formats, Types, or Variants

Input accepts hex with or without `0x` prefix and arbitrary whitespace. Output is rendered as space-separated lowercase hex bytes for clarity. Word sizes of 2, 4, and 8 bytes correspond to 16-, 32-, and 64-bit integers respectively. Multiple words are swapped independently: with a 4-byte word size, 12345678 9ABCDEF0 becomes 78 56 34 12 followed by F0 DE BC 9A.

Common Pitfalls and Edge Cases

The input must be a whole number of bytes (even number of hex digits) and a whole number of words (divisible by the configured word size in bytes). Mismatched sizes return an error rather than silently truncating. Network byte order is always big-endian, while x86 / ARM use little-endian — swap the bytes when reading or writing wire-format integers.

When to Use This Tool vs Code

Use the browser tool for one-shot conversions while reading binary dumps or debugging. In code, prefer `DataView` with explicit `littleEndian` flags in JavaScript, `byteorder='little'|'big'` in Python's `int.from_bytes`, `binary.LittleEndian.Uint32` in Go, or `ntohl` / `htonl` in C — these are clearer about intent and avoid hex round-trips.