What is the SIS file format?
.sis files store installation packages for Symbian OS applications. SIS stands for Software Installation Script. A .sis file bundles application data archives - containing .exe or .app executables - together with installation scripts that direct the Symbian installer to place files in the correct device locations.
What is Symbian OS?
Symbian is an older, now obsolete operating system for mobile devices from the era before modern smartphones. Symbian was used in devices manufactured by Nokia, Sony Ericsson, Motorola, and Samsung, powering the majority of GSM smartphones at its peak. The format originated in 1997 with Psion's EPOC platform before Nokia and partners adopted it as Symbian OS. Symbian OS uses .sis files to install applications.
Internally, .sis is a binary format with a fixed header of four UID fields plus a CRC checksum - unlike its successor .sisx, which is a ZIP-based package with mandatory cryptographic signing. Symbian OS 9.1 (2005) replaced the older .sis format with .sisx. Nokia shipped its last Symbian phone around 2012, and all associated PC tools are now end-of-life.
Installing SIS files
Before installation, the .sis file must be saved to the device's memory card or internal storage. Dedicated software tools, such as Nokia PC Suite, existed to aid users throughout the transfer process. Once transferred, the .sis file can be opened on-device and the installation script launches automatically.
Security & safety
RISK: MEDIUMSIS files can install arbitrary code on Symbian devices. Historically, Symbian malware (e.g. Cabir worm, 2004) spread as fake SIS packages. Since Symbian is abandoned, risk is limited to emulator contexts. No modern anti-malware actively targets SIS.
Format details
in a nutshell- SIS (Psi/EPOC RCOM Session) - Unrelated .sis files exist in some RCOM/PsiWin contexts but are rare - same extension, different format.
Programs that open SIS files
Windows4 apps
Nokia Suite
Free EOL December 2014 - final version 3.8.54; used to transfer SIS to phone via USB/Bluetooth. 
EKA2L1 (Symbian emulator)
Open-source Emulates Symbian OS 9.x; install .sis/.sisx apps via the emulator's package manager. Technical details
deep spec| Container | Custom binary (not ZIP; SISX successor is ZIP-based) |
| Encoding | Binary |
| Byte order | Little-endian |
| Header | Four UID fields (UID1-UID3 identify app and SIS variant; UID4 = CRC16 of preceding UIDs) |
| Magic bytes | UID2 = 0x1000006D (EPOC R3-R5) or 0x10003A12 (EPOC R6) at offset 4 |
| Checksum | CRC16 over UID1+UID2+UID3 stored in UID4; no whole-file integrity hash |
| Compression | zlib DEFLATE on file data (EPOC R6); EPOC R3-R5 files are uncompressed |
| Structure | Fixed header, language list, file list, requisite list, component list, file data blocks |
| Typical size | 10 KB - 50 MB |
| Platform | Symbian OS / EPOC; Windows used for PC-side transfer tools (Nokia PC Suite, Nokia Suite) |
| Format variants | EPOC R3-R5 (uncompressed, UID2=0x1000006D) and EPOC R6 (compressed, UID2=0x10003A12) |
| Encryption | None (SISX added mandatory PKI certificate signing) |
| Superseded by | .sisx for Symbian OS 9.1+ (2005); SISX is ZIP-based with mandatory code-signing certificate |
| Introduced | 1997 with Psion Series 5 (EPOC R3) |
| Released | 1997 (EPOC/Psion Series 5) |
| Latest version | Symbian OS 9.x SIS format (2005); superseded by SISX for Symbian 9.1+ |
| Specification | thoukydides.github.io |
SIS conversions
Community Q&A
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