.CIR File Extension Reference
The .CIR file format stores geometric modeling data, parametric primitives, mesh coordinates, and spatial rendering definitions for computer-aided design workflows. Files with the .CIR extension are categorized under CAD & 3D and are widely utilized in modern computing environments for storing, rendering, and exchanging structured data. By verifying the header signature (41 43 31 30) using forensic byte inspection tools, users can authenticate file integrity and rule out disguised executable payloads.
Quick Specification & Metadata
.CIR
CAD & 3D
text/plain
SPICE simulation ecosystem, Spectrum Software, and other electronics-software developers
N/A
Proprietary / Patent Licensed
Binary Header Data
2 MB - 100 MB
Online .CIR Viewer & Live Inspector
Open, inspect, zoom, and export .CIR files directly in your web browser. 100% private in-memory processing.
Drop your .CIR file here or browse
Inspect and preview any .CIR file securely with zero server uploads.
What is a .CIR File? (Technical Definition & Architecture)
The .CIR file format stores geometric modeling data, parametric primitives, mesh coordinates, and spatial rendering definitions for computer-aided design workflows. Files with the .CIR extension are categorized under CAD & 3D and are widely utilized in modern computing environments for storing, rendering, and exchanging structured data. By verifying the header signature (41 43 31 30) using forensic byte inspection tools, users can authenticate file integrity and rule out disguised executable payloads.
Formatted byte alignment adhering to international format specifications.
Adheres to formal schema and protocol documentation.
Parsed and executed identically across Windows, macOS, and Linux kernels.
CIR Binary Structure & Header Specifications
The .CIR format organizes data into validated sequential or hierarchical byte structures. Inspecting the header offset reveals the magic byte sequence 41 43 31 30.
- File Signature (Magic Bytes): 41 43 31 30
- MIME Content-Type: text/plain
- Payload Structure: Optimized data stream with metadata headers and checksum records.
- Safety Classification: Medium Risk – Inspect a CIR file as plain text first and identify whether it is a SPICE netlist, a Micro-Cap schematic, or another tool-specific circuit file Run simulations only with trusted model libraries and review directives that reference external files, behavioral sources, or automated commands Keep the original CIR file and any referenced .LIB, .MOD, model, and measurement files together before opening or simulating it Do not rename a CIR file to .SCH or .CIRC; use the originating application to save or export it in another circuit format Files ending in .CIR should always be inspected for valid magic bytes to verify they match legitimate CAD & 3D specifications.
How to Open .CIR Files on Windows, Mac & Android
- 1Primary Application: Double-click or open directly with NI Multisim.
- 2Alternative Software: Open using LTspice.
- 3File Association: Right-click the file, select Open with > Choose another app, and check Always use this app.
- 1Native macOS Application: Open with NI Multisim.
- 2Quick Look Preview: Highlight the file in Finder and tap the Spacebar.
- 3Set Default App: Press Cmd + I, expand Open with, select your application, and click Change All.
- 1Compatible Mobile Apps: Download a dedicated viewer for .cir from the Google Play Store.
- 2Cloud Storage: Open through Google Drive, Dropbox, or OneDrive mobile apps.
- 3Online Browser Conversion: Use AnyFileX mobile browser tools to convert the file into universal PDF or image formats.
Convert .CIR Files Online & Free
Convert your .CIR files directly into standardized .DWG format with high precision and zero privacy compromises.
Export .CIR files to .PDF for universal cross-platform viewing, printing, and sharing.
.CIR MIME Types & HTTP Server Headers
When serving .cir files over HTTP or configuring REST APIs, web servers must send the official IANA registered Content-Type headers:
| MIME Type Identifier | Standard Usage | File Extensions | Copy |
|---|---|---|---|
| text/plain | Standard official MIME type for .cir files | .cir |
# Nginx mime.types
types {
text/plain cir;
}
# Apache .htaccess
AddType text/plain .cir.CIR Magic Bytes & Hex File Signatures
In digital forensics and file signature analysis, authentic .cir files begin with a standardized magic byte sequence at byte offset 0x00 to verify file integrity and prevent extension spoofing:
Offset 0x0041 43 31 30CIRCAD & 3D File Format.CIR vs .DWG (Detailed Format Comparison)
| Feature Metric | .CIR | .DWG | Advantage |
|---|---|---|---|
| Format Full Name | CIR File Format | AutoCAD Drawing Database | Tie / Equal |
| Category | CAD & 3D | CAD & 3D | Tie / Equal |
| MIME Content-Type | text/plain | image/vnd.dwg | Tie / Equal |
| Binary Header (Magic Bytes) | 41 43 31 30 | 41 43 31 30 (AC10...) | Tie / Equal |
| Typical Storage Footprint | 2 MB - 100 MB | 2 MB – 120 MB | Tie / Equal |
| Universal Native Support | High / OS Standard | High / OS Standard | Tie / Equal |
.CIR Compatibility Matrix
Supported natively or through NI Multisim
Supported natively or via LTspice
Supported via open-source tools and command line utilities
Accessible through compatible mobile viewers or cloud previewers
Supported through dedicated mobile apps or cloud viewers
Accessible via web browser applications and Chrome extensions
Recommended Software for .CIR
NI Multisim
National Instruments
LTspice
Analog Devices
ngspice
SPICE simulation ecosystem, Spectrum Software, and other electronics-software developers
PSpice
SPICE simulation ecosystem, Spectrum Software, and other electronics-software developers
Micro-Cap
SPICE simulation ecosystem, Spectrum Software, and other electronics-software developers
Visual Studio Code
Microsoft Corporation
AnyFileX File Identifier
SPICE simulation ecosystem, Spectrum Software, and other electronics-software developers
Common Errors & Troubleshooting .CIR Files
Security & Malware Risk Assessment
Can a .CIR file carry viruses or malware?
Inspect a CIR file as plain text first and identify whether it is a SPICE netlist, a Micro-Cap schematic, or another tool-specific circuit file Run simulations only with trusted model libraries and review directives that reference external files, behavioral sources, or automated commands Keep the original CIR file and any referenced .LIB, .MOD, model, and measurement files together before opening or simulating it Do not rename a CIR file to .SCH or .CIRC; use the originating application to save or export it in another circuit format Files ending in .CIR should always be inspected for valid magic bytes to verify they match legitimate CAD & 3D specifications.
May support scripting or automation macros
Safe to inspect with AnyFileX's browser sandbox
- •Verify file extension in OS File Explorer options ('Show known file extensions').
- •Verify magic bytes (41 43 31 30) to ensure the file isn't a renamed executable.
- •Do not open .CIR attachments received unexpectedly via email or instant messenger.
Frequently Asked Questions
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