What is the GSP file format?
.gsp is the document format for The Geometer's Sketchpad, the dynamic geometry software originally developed at Swarthmore College and later published by Key Curriculum Press (subsequently McGraw-Hill Education). Each .gsp file stores an interactive geometric construction - points, lines, circles, polygons, arcs, and transformations - together with the full dependency graph that makes objects update dynamically when parent objects are moved.
A sketch can include multiple pages, measurements, custom tools and scripts, animation parameters, and labels. The construction history is preserved so Sketchpad can replay the steps that produced each object. Files are compact, typically 3 KB to 330 KB, reflecting the format's vector nature - it stores mathematical relationships, not pixel data.
The format is proprietary binary with no published specification. Files created in Sketchpad 5 may not open in older versions. The software ran on Windows (versions 3-5) and macOS (versions 1-5).
McGraw-Hill announced the retirement of Geometer's Sketchpad in 2019 and ended support on July 1, 2020. Installed copies continue to run but receive no updates and may develop OS compatibility issues over time. The educational community has largely migrated to GeoGebra, a free, open-source, web-based alternative whose .ggb files serve a similar role. There is no official conversion tool from .gsp to .ggb.
Security & safety
RISK: LOWProprietary binary geometry data with no executable content. Safe to open in Geometer's Sketchpad. EOL software carries OS-compatibility risk over time but not security risk.
Format details
in a nutshell- IMail Server Error Message File (Ipswitch) - Ipswitch's IMail Server used .gsp for error/status message template files - a completely unrelated server application format.
- Graphtec Plotter Cut File - Graphtec vinyl cutters use .gsp for cut/design files (vector plotter paths).
Programs that open GSP files
Windows1 app
The Geometer's Sketchpad 5
Paid File > Open - opens .gsp directly. Note: software is EOL (no support since July 2020); may have issues on Windows 11. 
macOS1 app
The Geometer's Sketchpad 5
Paid File > Open. Note: EOL July 2020; macOS Catalina+ (64-bit only) broke compatibility with Sketchpad 5 on some systems. Technical details
deep spec| Encoding | Binary, proprietary (no public specification released by vendor) |
| Byte order | Undocumented; likely big-endian given Mac-only origins (Sketchpad 1 was Macintosh-only) |
| Platform | Windows (Sketchpad 3-5), macOS (Sketchpad 1-5) |
| Content | Geometric objects (points, lines, circles, polygons, arcs), construction dependency graph, measurements, transformations, custom tools, animation parameters, labels |
| Dynamic behavior | Construction dependency graph preserved - child objects recompute automatically when parent objects are dragged |
| Multi-page support | Yes - a single .gsp file can contain multiple sketch pages |
| Typical file size | 3 KB - 330 KB (vector geometry only; no embedded raster data in typical use) |
| Magic bytes | None documented; file identified by .gsp extension only |
| Compression | None apparent |
| Version compatibility | Sketchpad 5 files may not open in earlier versions; no public version field documented |
| End-of-support date | July 1, 2020 (McGraw-Hill retired the product) |
| Migration path | No official conversion tool to GeoGebra .ggb; de facto community successor |
| Released | 1991 (The Geometer's Sketchpad v1 for Macintosh) |
| Latest version | Sketchpad 5.x (final version; EOL July 1, 2020) |
GSP conversions
Community Q&A
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