IMSI Parser
Decode an IMSI into MCC, MNC and MSIN per ITU-T E.212 and 3GPP TS 23.003 — with the 2-vs-3-digit MNC ambiguity resolved and raw EF_IMSI decoding.
IMSI structure
An IMSI is at most 15 digits: a 3-digit MCC (mobile country code, ITU-T
E.212), a 2- or 3-digit MNC (mobile network code) and the remaining
MSIN that identifies the subscriber within that network. It is stored in
EF_IMSI (6F07) inside ADF_USIM.
The 2-vs-3-digit MNC trap
Generic decoders guess the MNC length and get North America wrong. The correct MNC length is carried in
EF_AD (administrative data) on the card, and mandated as 3 digits for certain MCCs. This tool
presents both splits and flags the E.212-preferred one instead of silently guessing.
FAQ
How do I know if the MNC is 2 or 3 digits?
You can't tell from the IMSI alone. Most countries use a 2-digit MNC; parts of North America (MCC 302, 310–316) and a few others use 3 digits. This tool marks the E.212-preferred split but always shows both interpretations so you can cross-check against EF_AD (which records the MNC length) or your HLR/HSS config.
The operator name doesn't match the SIM's brand — why?
For MVNOs the IMSI MNC identifies the host network that owns the numbering, not the retail brand. A SIM branded X may carry an IMSI whose MNC belongs to host operator Y.
Can it decode raw EF_IMSI bytes?
Yes. Paste the EF_IMSI (6F07) content — a length byte, a parity nibble, then swapped-nibble BCD digits — and the tool reports the length byte, parity and the reconstructed IMSI before decoding MCC/MNC/MSIN.
Related tools
Need this at production scale?
Senior SIM/USIM/OTA consulting, applet development and operator advisory — EN/PT.