Free Tool

Stop Guessing Byte Orders

Decode Modbus hex data to floats, integers, and timestamps instantly. Try all byte order combinations with one click. Works offline, no signup required.

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Modbus Hex Decoder interface showing hex to float conversion

Why Engineers Trust This Decoder

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All Byte Orders

ABCD, DCBA, BADC, CDAB - decode all byte swap combinations simultaneously. No more trial and error.

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CRC Validation

Paste entire RTU frames and get automatic CRC-16 validation. Instantly know if your frame is valid.

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Instant Results

See all possible decodings as you type. No submit buttons, no waiting. Real-time feedback.

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Privacy First

Everything runs in your browser. Your Modbus data never leaves your device. Works offline too.

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Frame Parsing

Paste raw RTU or TCP frames. Auto-detect slave address, function code, and register data.

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Multi-Format

Decode to 32-bit floats, 16/32-bit integers, timestamps, and more. All from one input.

Powerful Decoding Features

Decode All Byte Orders at Once

Stop the guessing game. Enter your hex data once and see the decoded value in all four byte order combinations: ABCD (Big Endian), DCBA (Little Endian), BADC (Mid-Big Endian), and CDAB (Mid-Little Endian).

  • Instant comparison across all byte orders
  • Highlight the most likely correct interpretation
  • Works with 32-bit floats and integers
All four byte order decodings shown side by side

Parse Complete RTU Frames

Paste an entire Modbus RTU frame and get automatic parsing. The tool extracts slave address, function code, register addresses, data values, and validates the CRC-16 checksum.

  • Auto-detect frame structure
  • CRC-16 validation with error highlighting
  • Support for Function Codes 03, 04, 06, 16
RTU frame parsing with annotated fields

IEEE 754 Float Visualization

See exactly how your hex data maps to IEEE 754 floating point format. Understand the sign bit, exponent, and mantissa breakdown for debugging precision issues.

  • Visual bit layout diagram
  • Exponent and mantissa values
  • Handle special cases (NaN, Infinity)
IEEE 754 format breakdown visualization

Common Questions

This usually means the byte order is wrong. Modbus has no standard for byte order, so different devices use different conventions. Try all four byte orders (ABCD, DCBA, BADC, CDAB) - one should give you a reasonable value. If you're getting values like 1e38 or -1e38, that's a sign of byte order mismatch.
ABCD (Big Endian): Most significant byte first.
DCBA (Little Endian): Least significant byte first.
BADC (Mid-Big): Word-swapped big endian.
CDAB (Mid-Little): Word-swapped little endian.

Most Siemens PLCs use ABCD, while many others use CDAB. When in doubt, try all four!
Modbus RTU uses CRC-16 with polynomial 0x8005, initial value 0xFFFF, and reflected input/output. Common mistakes include: sending ASCII hex instead of raw bytes, wrong byte order in the CRC itself (it's transmitted LSB first), or having extra bytes in the frame. Our tool calculates and compares automatically.
Yes! Just paste the hex data from multiple registers. For example, if you read 4 registers (8 bytes), paste all 8 bytes and the tool will decode them as two 32-bit floats or four 16-bit integers.
Yes! Modbus TCP and RTU use the same data encoding for register values. The only difference is the framing - TCP uses a header instead of CRC. You can paste just the register data portion and decode it the same way.
No. Everything runs entirely in your browser using JavaScript. Your Modbus data never leaves your device. You can even use this tool offline - try disconnecting from the internet and it still works!

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