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Reverse Hex Digits

Reversing hex can mean three different things: reverse the entire string ("ABCD" → "DCBA"), swap byte order ("12 34 56 78" → "78 56 34 12" — endianness conversion), or swap nibbles within each byte ("AB" → "BA"). Each has different uses. The ZTools Reverse Hex tool offers all three modes. Most common use: byte-order swap, when converting between little-endian (Intel) and big-endian (network protocols) representations.

Use cases​

Convert between little-endian and big-endian​

Network protocols use big-endian; x86/ARM use little-endian. A 32-bit value 0x12345678 is stored as 78 56 34 12 in memory but transmitted as 12 34 56 78. Tool swaps in either direction.

Match a checksum / hash​

Some tools display CRC / hash bytes in reverse order. Reverse to match the canonical representation.

Debug endian-confusion bugs​

A C struct serialised differently than expected — reverse the bytes to confirm endianness mismatch.

Generate test vectors with reversed input​

Test that your code handles both endiannesses correctly by feeding it both forms.

How it works​

  1. Paste hex — With or without spaces / 0x prefixes. Whitespace stripped.
  2. Pick mode — Reverse string (full reversal char-by-char), swap bytes (reverse byte order), or swap nibbles (within each byte).
  3. Compute — String reversal is straight; byte swap chunks 2 chars at a time; nibble swap flips within each pair.
  4. Output — Result hex string in the same format (spaces preserved or removed per input).

Examples​

Input: "12 34 56 78", swap bytes

Output: "78 56 34 12" — little-endian → big-endian (or vice versa).

Input: Same input, reverse string

Output: "87 65 43 21" — full string reversal, also swaps nibbles within each byte.

Input: "AB CD", swap nibbles

Output: "BA DC" — within each byte the high and low nibbles flip.

Frequently asked questions​

Which mode for endianness?

Swap bytes. The byte order changes; the bits within each byte stay the same. This is the typical little-endian ↔ big-endian conversion.

When would I want full string reversal?

Rarely — full reversal is mathematically a different operation. Mostly useful for puzzle / curiosity work.

How big a hex string?

Megabytes work fine. The reversal is O(n).

Privacy?

All in browser.

Tips​

  • For endianness, almost always pick "swap bytes" — preserves byte values, changes order.
  • For network-order (big-endian) data on x86 (little-endian), htonl / ntohl in C does this; tool does it in browser.
  • Don't confuse with reversing bit order — that's a separate operation (use Invert Binary Bits with caution).

Try it now​

The full Reverse Hex Digits runs in your browser at https://ztools.zaions.com/reverse-hex — no signup, no upload, no data leaves your device.

Open the tool ↗

Last updated: 2026-05-06 · Author: Ahsan Mahmood · Edit this page on GitHub