How does this reverse DoubleHex?

Since hex-to-doublehex-converter writes every digit twice in a row, this tool just keeps every 2nd digit, starting from the first one (indexes 0, 2, 4, ...), and discards the rest. For genuine DoubleHex input, that recovers the original string exactly.

What if I paste in a hex string that wasn't actually produced by DoubleHex?

This tool doesn't check whether consecutive digits actually match each other before dropping half of them; it just always takes every 2nd digit. Feed it "ABCD" (never doubled in the first place) and it will still confidently return "AC", silently dropping B and D. That's expected behavior for this invented format, not an error condition, since there's no way to detect "was this really doubled" from the string alone.

Is this a lossy or lossless conversion?

For genuine DoubleHex input (i.e. output that actually came from hex-to-doublehex-converter), it's completely lossless, you get back exactly what went in originally. It only becomes effectively 'lossy' if you feed it something that was never actually doubled to begin with, in which case it isn't really reversing anything, it's just taking every other character.

Why not validate that digit pairs match before removing half of them?

Because DoubleHex's whole design is simple and mechanical: reverse it the same simple, mechanical way. Adding pair-matching validation would turn a one-line de-duplication into a stricter format checker, which isn't what this novelty tool set out to be. If you want to confirm your input is genuine DoubleHex, compare consecutive digit pairs yourself before running it through this tool.

DoubleHex to Hex Converter - Undo DoubleHex Duplication Online

Overview

Introduction

This tool reverses hex-to-doublehex-converter's transform by keeping every 2nd digit of the input and discarding the rest, halving the string's length back toward the original.

For genuine DoubleHex input, this is a fully lossless round trip; the format was designed so nothing is thrown away in the forward direction, so nothing needs to be recovered here beyond simple de-duplication.

What Is DoubleHex to Hex Converter?

DoubleHex-to-Hex is the designed inverse of DoubleHex: it walks the input two digits at a time and keeps only the first digit of each pair, producing an output exactly half the length of the input.

It performs no validation that the two digits in each pair actually match; it simply always keeps the first of every pair.

How DoubleHex to Hex Converter Works

The input is validated to contain only hex digits (0-9, A-F, case-insensitive), an optional leading 0x or # is stripped, then the tool iterates over the string at even indices (0, 2, 4, ...) and collects those characters.

The resulting digits are joined and uppercased. If the input length is odd, the trailing unpaired digit is included as-is; genuine DoubleHex output is always even-length, so this only comes up with malformed input.

When To Use DoubleHex to Hex Converter

Use this specifically to reverse output you already generated with hex-to-doublehex-converter, to get back your original hex string exactly.

Avoid feeding it arbitrary hex strings expecting a meaningful result; if the input wasn't actually produced by doubling, this tool will still run, but the result is just 'every other digit', not a real decoding.

Often used alongside Hex to DoubleHex Converter and HalfHex to Hex Converter.

Features

Advantages

Perfectly lossless for genuine DoubleHex input, recovering the exact original string.
Simple, fast, single-pass de-duplication with predictable output length (always half the input's).
No ambiguity in how it processes input, always the digit at each even index.

Limitations

Performs no validation that consecutive digit pairs actually match; it will happily process non-doubled input and silently discard half its digits.
There is no way to detect from the output alone whether the input was genuinely produced by hex-to-doublehex-converter.
This is an invented format specific to this site, not a real or external standard.

Examples

Reversing a genuine DoubleHex string

Input

11AA

Output

1A

Keeping the digit at index 0 ('1') and index 2 ('A') recovers the original 2-digit hex string exactly.

Feeding in a string that was never actually doubled

Input

ABCD

Output

AC

This wasn't produced by hex-to-doublehex-converter (no digit repeats), but the tool doesn't know that; it just keeps the digits at indexes 0 and 2, silently dropping B and D. This is expected, documented behavior for this invented format, not an error.

Best Practices & Notes

Best Practices

Only rely on this tool for a meaningful result when the input genuinely came from hex-to-doublehex-converter.
If you're unsure whether a string is genuine DoubleHex, manually check that consecutive digit pairs match before trusting the output.
Use it together with hex-to-doublehex-converter as a quick lossless round-trip sanity check.

Developer Notes

Implementation walks the (validated, uppercased) input in steps of 2, pushing the digit at each even index into the output array; it never compares digit[i] to digit[i+1]. This mirrors the format's own simplicity: DoubleHex was designed to be trivially reversible for real doubled input, not to be a validator.

DoubleHex to Hex Converter Use Cases

Recovering the original hex string from genuine hex-to-doublehex-converter output
Demonstrating a lossless round trip together with hex-to-doublehex-converter
Illustrating, by contrast, what happens when a 'de-duplication' assumption is applied to input that doesn't actually satisfy it

Common Mistakes

Assuming this tool validates that the input was genuinely doubled; it doesn't, it always just keeps every 2nd digit.
Expecting a meaningful result from arbitrary hex input that was never produced by hex-to-doublehex-converter.
Forgetting that an odd-length input leaves a trailing unpaired digit included as-is, which only happens with malformed DoubleHex.

Tips

Round-trip through hex-to-doublehex-converter and back to confirm you get your original string exactly.
If the output looks wrong, check whether every digit in your input actually appears twice in a row; if not, this tool's output isn't meaningful.

DoubleHex to Hex Converter