Opening a CIR File

The CIR file type is primarily associated with LTspice.

CIR	File extension: CIR
	File type:	circuit simulation file

What is a CIR file?

CIR files mostly belong to LTspice. CIR files are mostly used for electronic circuit simulation and design. They usually contain a netlist – a text description of circuit components and their connections – which is understood by SPICE-based simulators.
Key use cases:

SPICE simulation input for tools like LTspice, ngspice, AimSpice, Xyce, and CircuitLogix.

Circuit design files as seen with Micro-Cap and Logisim.

Compressed project files in some cases (for example, zipped Fiber Optic Projects from CIRCAD).

Specialized data used by Racelogic systems.

These files are often in plain text or XML and sometimes compressed via ZIP. When you open a CIR file in a text editor, you can see the simulation commands and component listings written in a standard netlist format. This standard, originally based on SPICE, ensures that several simulation programs can interpret them correctly.
FilExt.com tip: For more technical details, visit the ngspice website or the LTspice page.

How do you open CIR files?

You need a suitable software like LTspice to open a CIR file. Without proper software you will receive a Windows message "How do you want to open this file?" or "Windows cannot open this file" or a similar Mac/iPhone/Android alert. If you cannot open your CIR file correctly, try to right-click or long-press the file. Then click "Open with" and choose an application. You can also display a CIR file directly in the browser:. Just drag the file onto this browser window and drop it.

Online CIR Text Viewer

Choose your .cir file to view

or drag and drop it here

Online File Viewer

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How to extract texts from CIR files or capture a screenshot to PDF, JPG, DOCX, TXT, ...

If you want to extract texts from CIR file or capture a screenshot, you can use our free Online CIR File Viewer:

Just click the "Choose your .cir file to view" button on this page.
After your file is opened in browser,
click "Save as..." in the menu.
Then choose the file format (e.g. JPG, PDF, DOCX, TXT, ...) you want.
Download the converted file.

Programs that open and convert CIR files:

LTspice
See the previous paragraphs to learn more about the main application. CIR files are often referred to as LTspice cads because this type of file is primarily created or used by this software.
PSpice (Circuit File) by Cadence Design Systems, Inc.
PSpice is a SPICE analog circuit and digital logic simulation software that runs on personal computers (thus the first letter P in its name). It was developed by MicroSim and used in electronic design automation. MicroSim was bought by OrCAD which was subsequently purchased by Cadence Design Systems. The name is an acronym for Personal Simulation Program with Integrated Circuit Emphasis. Today it has evolved into a analog mixed signal simulator. This file format is classified as Text.
real-PCB (Netlist) by Crocodile Clips Ltd
real-PCB is a new add-on for Crocodile Technology 410, which imports your electronic circuit simulations and converts them to PCB layouts. This file format is classified as CAD/CAM.
SuperMax E-CAD Save-File Command

CIR format details:

To find out what program is needed to open CIR files, you need to determine the file format. The first characters in a file identify the file format, for example, HTML files start with the bytes <html>. Nonetheless, different programs can utilize the same file extension to represent distinct file formats. Double-clicking on the file often results in an error when opening. Knowledge is power - this also applies when dealing with unknown or faulty files. Below is our analysis of the CIR files:

The CIR file extension is very common and has no uniform or dominant file format. But the following two file formats are common:

15% of all CIR files start with the magic bytes [Main], which are always the first bytes of this file format. The content consists of readable text data, which can be read using a text editor. The files are often between 13 KB and 50 KB in size. The file type was created 10 years ago, but is still used today. Certain words are almost always found in the files, such as MCAPVersion, NLCnt, Program=Micro-Cap, Screen, TXCnt, [Main], FileType=CIR, [shapedef], Name, Component Version=10.00, Key ID=Demo, Shape Version=11.00 and Version=12.00. These files are often associated with circuit, tcoilschematic and schema.
4% of all CIR files use the same file format, which have the signature *********. These files are text files and can therefore be read using a text editor. The average file size is 4 KB with most files being between 1 KB and 7 KB in size. The files contain the following words: Model. The following filename is common: AD8232.cir.

All other CIR files (81%) have no consistent format, the following 18 formats exist: ZIP, XML, UTF-8, Java, Source, aimspice, Lab, Automatically and nmos. These files are often connected to spice, nmos, assignment, vary, orange, analysis or inverter. You can get all the details of your CIR file by dragging it onto this page or by clicking the button "Choose your .cir file to view" above.

Technical Data for CIR File Extension

File classification:

CAD

Related files:

asc, net, sp, circ, txt, icircuit, zip, bak_cir, ms14, net, rar, lib, tno, out, spi, inx, log, pdf, dat, ano, exe, prb, xml

The following listing is compiled from the database produced by the 'Associate This!' program, selected data from the main FILExt database and file extension information submitted by users.

ProgramID: OrCADPSpiceAD10.0.0.cir
EXEFile: C:\OrCAD\OrCAD_10.0_Demo\tools\PSpice\pspice.exe %1

ProgramID: OrCADPSpiceAD10.5.0.cir
EXEFile: C:\OrCAD\OrCAD_10.5_Demo\tools\PSpice\pspice.exe %1

ProgramID: OrCADPSpiceADLE9.20.cir
EXEFile: %ProgramFiles%\OrcadLite\PSpice\pspice.exe

ProgramID: LTspice.Netlist
EXEFile: %ProgramFiles%\LTC\SwCADIII\scad3.exe

ProgramID: RealPCB.CirFile
EXEFile: %ProgramFiles%\RealPCB\realPCB.exe

Show all 5 listings To Top

a cir circuit simulation file is a special file format and should only be edited and saved with the appropriate software.

How to solve problems with CIR files

Associate the CIR file extension with the correct application.
Update your software that should actually open circuit simulation files. Because only the current version supports the latest CIR file format. Search, therefore, e.g. on the manufacturer website after an available LTspice update.
To make sure that your CIR file is not corrupted or virus-infected, get the file again and scan it with Google's virustotal.com.
Click here to open your .CIR file online - secure, fast, and no downloads needed.