SMPP tool · flagship

SMPP PDU Decoder

Paste raw SMPP hex — one PDU or a whole captured stream — and get a field-by-field decode with byte offsets, command_status explanations, TLV expansion, DCS/charset handling, UDH parsing and concatenation reassembly.

100% client-side — your PDUs never leave your browser

Paste SMPP hex (one or more PDUs; spaces, 0x, colons, tcpdump -X all fine)

Raw bytes

No bytes to decode.

How the decoder works

The tool frames the input on command_length, decodes the 16-octet header, then walks the mandatory body for the specific command_id and finally the optional TLV stream. Bitfields like esm_class and registered_delivery are expanded to named flags, and data_coding is decoded per SMPP and GSM 03.38 so the message text renders in the right charset.

Edge cases it handles

sm_length not matching the actual short_message — decoded anyway, flagged.
Both short_message and message_payload present (spec-invalid, seen in the wild).
Truncated PDUs and command_length beyond the input — partial decode.
Vendor-specific TLV tags (0x1400–0x3FFF) decoded structurally and labelled.

FAQ

What SMPP versions and PDU types does it decode?

SMPP v3.4 fully and v5.0 PDUs and TLVs on top — all bind variants, submit_sm, deliver_sm, data_sm, query/cancel/replace, enquire_link, alert_notification, generic_nack and the v5.0 broadcast family.

Is my data uploaded anywhere?

No. Parsing runs entirely in your browser with JavaScript. Nothing is sent to a server, and the shareable permalink stores the input in the URL fragment, which is never transmitted.

Can it decode a delivery receipt?

Yes. A deliver_sm carrying a receipt is detected and its Appendix B text (id, sub, dlvrd, stat, err, text) is broken out, with the stat value explained.

Does it handle concatenated (multipart) messages?

Yes. Paste all segments and it groups them by UDH concat header or sar_* TLVs, reassembles the text, and flags any missing segment.

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