What is the TNS file format?
.tns files are used by graphing calculator devices of the TI-Nspire series, developed by Texas Instruments. Internally, a .tns file is a ZIP-based document container that holds a Document.xml file along with per-problem and per-page definitions, application data, optional Lua or TI-Basic programs, and embedded image resources. Early files created with TI-Nspire OS before version 1.2 were plain ZIP archives readable by standard tools; since OS 1.2, Texas Instruments switched to a proprietary compression wrapper, so modern .tns files cannot be opened by standard ZIP utilities even though the internal structure remains ZIP-like.
.tns files can hold various data and objects generated and used by TI-Nspire devices, including:
- graphs and geometric visualizations,
- images and graphics,
- tables and spreadsheets,
- mathematical formulas and calculations,
- Lua scripts and TI-Basic programs.
TI-Nspire data is stored in .tns project files. Besides storing data for TI-Nspire handheld devices, .tns files also serve as a data interchange format when exchanging content between handheld calculators and desktop software. They can be distributed over the internet, via email, or using portable storage devices.
A companion format, .tnsp (PublishView), supports richer computer-only layouts and can be converted back to .tns for transfer to a handheld. The MIME type for .tns files is application/vnd.ti-nspire.
Security & safety
RISK: LOWA .tns is a document, not a program you run on your PC, so it carries little direct malware risk; the embedded Lua/TI-Basic only runs inside the sandboxed TI-Nspire environment. The practical cautions are: (1) third-party online TNS-to-PDF converters require uploading the file, so don't use them for confidential class material, and (2) some sites advertising free '.tns viewers/openers' are ad-laden or bundle PUPs - prefer the official TI software or the documented community tools.
Format details
in a nutshellPrograms that open TNS files
Windows3 apps
TI-Nspire CX Teacher Software
Paid Install the software, then File → Open and select the .tns; create, edit and send documents to handhelds.
TI-Nspire CX Student Software
Paid Open the .tns to work through an activity; comes with TI-Nspire CX II handhelds or via subscription.
TI-Nspire CX Premium Teacher Software (trial)
Freemium Free time-limited trial; install to open and view a .tns before buying. 
macOS1 app
TI-Nspire CX Teacher/Student Software (macOS)
Paid Install the macOS build, then File → Open the .tns to view and edit.
TI-Nspire CX app (iPad)
Paid Open the .tns in the iPad app (import via Files/email) to view and edit on iPad.
convert.guru TNS converter
Free Upload a .tns to convert it to PDF/TXT/XML for viewing without TI software (online, third-party - avoid for sensitive content). Technical details
deep spec| Developer | Texas Instruments |
| Format type | Proprietary ZIP-based document container (binary) |
| MIME type | application/vnd.ti-nspire |
| Internal document format | XML; primary entry is Document.xml plus per-problem and per-page application data |
| Container base | ZIP (PKZIP); files from OS < 1.2 are standard ZIP; OS 1.2+ wraps data in TI proprietary compression |
| Compression | DEFLATE (pre-OS 1.2 files) / TI proprietary undocumented compression (OS 1.2+ files) |
| Magic bytes | 50 4B 03 04 ('PK' ZIP header) in early files; modern files do not carry a reliable standard signature |
| Byte order | Little-endian |
| Embedded content types | Graphs, geometry, lists and spreadsheets, Notes pages, Lua scripts, TI-Basic programs, images |
| Standard ZIP tool compatibility | Only with pre-OS-1.2 files; modern files require TI-Nspire software to open |
| Platform support | Windows, macOS, iPadOS (TI-Nspire CX app), TI-Nspire handheld OS |
| Typical file size | A few KB to several MB, depending on the number of pages, problems, and embedded resources |
| Related extensions | .tnsp (PublishView), .tilb (library), .tno, .tcc |
| Released | 2007 (TI-Nspire handheld and software launch) |
| Latest version | Tracks TI-Nspire OS/software (CX II series, software v6.x as of 2026) |
| Specification | www.hackspire.org |
TNS conversions
Community Q&A
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