An SMS PDU is a hexadecimal representation of an SMS message used by modems, phones, SMS gateways, and telecom systems. It can include addressing, encoding, timestamp, message text, and control fields.

Can this tool encode every possible PDU?

No. It supports common SMS-DELIVER and SMS-SUBMIT decoding and basic GSM-7 outgoing SMS-SUBMIT encoding. Advanced features such as concatenated SMS, binary messages, flash SMS, national language tables, and carrier-specific behavior may require specialist tools.

Does this PDU decoder upload my message?

The tool is designed to process PDU text in your browser. Avoid adding private phone numbers, OTPs, customer messages, or sensitive telecom records unless your policy allows it.

SMS telecom tool

PDU Encoder Decoder Online

Decode SMS PDU hex into readable fields, or create a basic GSM-7 SMS-SUBMIT PDU from a destination number and message text.

Open PDU tool

Browser tool

Paste PDU hex or encode a simple SMS

To decode, paste SMS PDU hex. To encode, use To: +15551234567 on the first line and Message: Hello below it.

Upload PDU textDrag and drop or browseNo file selected

Input PDU or encode requestDecoded or encoded output

Paste PDU hex to decode, or enter To and Message lines to encode.

What is a PDU encoder decoder?

A PDU encoder decoder helps inspect or create the hexadecimal SMS format used by GSM modems, phones, SMS gateways, and telecom testing tools. A PDU can contain the service center address, sender or recipient number, protocol identifier, data coding scheme, timestamp, user data length, and message text. When an SMS gateway returns a raw PDU, decoding it makes the message much easier to troubleshoot.

This online PDU tool is designed for common debugging tasks: reading SMS-DELIVER messages received by a modem, inspecting SMS-SUBMIT messages prepared for sending, and creating a basic outgoing GSM-7 SMS-SUBMIT PDU for testing. It is not a full telecom lab suite, but it gives developers and support teams a quick browser-based way to understand ordinary PDU examples.

Examples

PDU decode and encode examples

Paste a raw PDU to decode it, or enter a number and message to generate an outgoing PDU.

Encode input example

To: +15551234567
Message: Hello from testing

Decoded output fields

{
  "type": "SMS-DELIVER",
  "smsc": "+12063130004",
  "sender": "+15551234567",
  "dcs": "0x00",
  "timestamp": "2026-08-04 10:30:00",
  "message": "Test message"
}

When to use this PDU tool

Use this PDU encoder decoder when working with SMS modems, AT commands, gateway logs, SIM testing, SMS troubleshooting, or telecom support cases. Developers often see PDU strings while testing commands such as AT+CMGL, AT+CMGR, or AT+CMGS. Instead of reading the hex by hand, paste it into the decoder to inspect the sender, recipient, DCS, timestamp, and message content.

The encode mode is useful when you need a simple outgoing PDU for a GSM-7 text message. Start the input with To:, add the destination phone number, then add Message: and the text. The output includes the SMS-SUBMIT PDU and a TPDU length value commonly needed by modem commands. Always test with your actual modem or gateway because device behavior can vary.

Common mistakes

PDU issues to watch for

Wrong phone number format

International numbers should usually start with +. The encoder uses international address type for plus-prefixed numbers.

Advanced SMS variants

Concatenated messages, binary SMS, flash SMS, UDH headers, and national language tables can require more specialized handling.

Unicode messages

The simple encoder is intended for common GSM-7 text. Messages with emoji or many non-GSM characters may need UCS-2 encoding.

Confusing PDU length

Some modem commands require the TPDU length, not the full hex string length. The encoder shows a common TPDU length value.

Privacy and local browser processing

The PDU encoder decoder is designed to run in your browser with client-side JavaScript. Pasted PDU text is processed locally by the page, and no account is required. Share links can include the PDU or message content you entered, so only create a link when the example is safe for another person to view.

SMS PDU strings may contain real phone numbers, timestamps, service center numbers, and message text. Do not paste private OTPs, customer SMS records, internal telecom logs, sensitive numbers, or confidential message content into any online tool unless your policy allows it. For support or documentation, create a small fake PDU example whenever possible.

FAQ

PDU Encoder Decoder FAQ

What is SMS PDU mode?

PDU mode is a modem SMS mode where messages are represented as hexadecimal protocol data units instead of plain text. It is common in AT command workflows and SMS gateway debugging.

Can this tool decode received SMS messages?

Yes, it supports common SMS-DELIVER decoding and shows readable fields such as SMSC, sender, timestamp, DCS, and message text when the PDU uses supported encoding.

Can this tool encode outgoing SMS messages?

Yes, it can create a basic SMS-SUBMIT PDU for GSM-7 text. Use a To line and a Message line in the input box.

Does it support every carrier PDU?

No. The tool covers common cases. Advanced telecom features such as UDH, concatenated SMS, binary payloads, and national language shift tables may need specialized telecom software.