Opening an STAR File

The STAR file type is primarily associated with RELION.

STAR	File extension: STAR
	File type:	text archive file

What is an STAR file?

STAR files mostly belong to RELION. STAR files are self-describing text files built on the Self-defining Text Archive and Retrieval concept. They store structured data in plain text form and include rules for interpreting the file content within the file itself.
In the field of cryo-electron microscopy, these files hold key metadata such as particle coordinates, microscope parameters, and processing details. Programs like RELION use this format to manage and analyze cryo-EM data. For more detailed information on the cryo-EM application of this format, visit the MRC-LMB website.
Another use of STAR files is seen in HP systems where they function as an ISO archive for software upgrades on HPE appliances. More on this role is available at the HPE Support site.
Key points about STAR files include:

Self-describing: They carry embedded structure definitions that allow programs to interpret the data without external schemas.

Plain text format: You can open them with any text editor to see the underlying data.

Structured layout: They often use loops and data blocks to organize detailed information efficiently.

FilExt.com tip: If you have a STAR file, you can view its content using a text editor. However, for proper use—especially in cryo-EM research or when handling system upgrades—specialized software like RELION or corresponding HP tools is recommended.

How to open an STAR file

You need a suitable software like RELION to open an STAR 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 STAR file correctly, try to right-click or long-press the file. Then click "Open with" and choose an application. You can also display a STAR file directly in the browser:. Just drag the file onto this browser window and drop it.

Online STAR File Viewer

Choose your .star file to view this image

or drag and drop it here

Online File Viewer

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

You can extract texts from STAR file or capture a preview screenshot using our online STAR file viewer:

To do this, click the button "Choose your .star file to view this image" on this page.
Your STAR file will then be displayed in the browser.
Now click on "Save as..." at the top of the page.
Then choose the file format (e.g. JPG, PDF, DOCX, TXT, ...) you want.
Your file will be converted and downloaded.

Programs that open and convert STAR files:

RELION
See the previous paragraphs to learn more about the main application. STAR files are often referred to as RELION simple text files because this type of file is primarily created or used by this software.
Apple II operating system

STAR file format:

Each file has a definite file format, that is, how the stored data is arranged in the file. The file format can be determined based on the file extension and the signature (the first few characters of a file). If the file extension does not match the file format, double-clicking on the file will cause an error upon opening. So you need a detailed analysis of a file to find out the format and the associated program. Our evaluation of the STAR files looks like this:

STAR is not a common file extension and does not have a uniform file format. The two most common formats are as follows:

20% of all STAR files have the same signature # version 30001 . The contents of these files are easily readable with a text editor. The files are often between 600 bytes and 8 MB in size. The files contain the following words: # version 30001, data, loop_ and general. Some examples of file names are default_pipeline.star or job.star. Such files are related to pipeline, model and data.
10% of all STAR files start with the magic bytes data_, which are always the first bytes of this file format. These files are text files and can therefore be read using a text editor. The average file size is 890 KB with most files being between 2 KB and 3 MB in size. Certain words are almost always found in the files, such as general, data_ and loop_. run_it025_model.star is a typical file name. These files are attributed to motion.

All other STAR files (70%) have different formats, frequently e.g. HPEssmcappliance and RELION. Tagged as appliance, upgrade, micrographs or particles. You can get all the details of your STAR file by dragging it onto this page or by clicking the button "Choose your .star file to view this image" above.

Technical Data for STAR File Extension

File classification:

Simple text file

Related files:

cif, ssj, star_data, ster, zip, nxs, v2, audio, txt, xml, json, cfg, dat

Mime type:

text/x-python

an star text archive file is a special file format and should only be edited and saved with the appropriate software.

How to solve problems with STAR files

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