Windows
Compatible applications
Quick Facts
Basic information about this file format
Extension
.QUAL
File Type
FASTA Quality File
Category
Data
Best first step
Use compatible software
Quick Summary
A practical overview of the .qual file format
The QUAL file format is a text-based format used in bioinformatics to store quality scores for DNA sequences, typically complementing a corresponding FASTA file. While the FASTA file contains the actual nucleotide sequence represented by characters like A, C, G, and T, the QUAL file provides numeri…
File extension
.QUAL
File type
FASTA Quality File
Category
Data
Recommended action
Open with a trusted compatible app
How to open a .qual file
Start with a trusted app that supports this format
- Check the file extension carefully and confirm that the file name really ends with .qual.
- Use software that supports this file type. If one app does not work, try another compatible program for the same platform.
- Update the application if the file was created by a newer version of the software.
- Scan files from unknown sources before opening them, especially documents, archives, scripts, installers, and executable files.
What is a .qual file?
File extension details and usage information
The QUAL file format is a text-based format used in bioinformatics to store quality scores for DNA sequences, typically complementing a corresponding FASTA file. While the FASTA file contains the actual nucleotide sequence represented by characters like A, C, G, and T, the QUAL file provides numerical values representing the confidence or probability of error for each base call, often using the Phred quality score scale. Each score corresponds to a specific position in the sequence. These files are essential in genomic research and DNA sequencing pipelines, as they allow researchers and software to filter out low-quality data or account for potential errors during sequence assembly and analysis. Although newer formats like FASTQ have largely superseded the separate FASTA/QUAL pair by combining sequence and quality data into a single file, the QUAL format remains relevant for legacy data and specific bioinformatics tools that require decoupled sequence and quality information. The format usually starts with a header line beginning with a 'greater than' symbol, followed by a series of integers separated by spaces or line breaks.
Software Compatibility
Programs that may open or work with .qual files
macOS
Compatible applications
Linux
Compatible applications
Mobile
Mobile applications
Can .qual files be converted?
Options for saving or exporting this file to another format
In many cases, a .qual file can be converted by opening it in compatible software and using an option such as Save As, Export, or Convert. The available output formats depend on the file type and the application used.
- Use the original software that created the file when possible.
- Check whether the application supports exporting to common formats.
- Be careful with online converters when working with private, business, or sensitive files.
- If conversion fails, the file may be corrupted, incomplete, encrypted, or not actually a .qual file.
Why can't I open a .qual file?
Common reasons this file type may not open correctly
Wrong software
The file may require a specific program that supports the .qual format.
Incorrect extension
The file extension may have been renamed manually, even though the actual file format is different.
Corrupted file
The file may be incomplete, damaged during download, or transferred incorrectly.
Outdated app
Your software may need to be updated before it can open newer versions of this file format.
Frequently Asked Questions
Common questions about .qual files
To open a .qual file, use software that supports this file format.
- Notepad++
- Geneious
- BioEdit
- CLC Genomics Workbench
- TextEdit
Open the file in compatible software and look for options such as Save As, Export, or Convert. If no export option is available, the file may require a specialized converter or the original application that created it.
- Verify that the file extension is correct.
- Install or update compatible software.
- Try another application that supports this format.
- Check whether the file is corrupted, incomplete, or encrypted.
A file extension alone does not guarantee whether a file is safe or unsafe. Only open files from trusted sources, scan unknown files before opening them, and be especially careful with executable, script, archive, and document files.
File safety tips
Use caution with unknown files
Only open files from trusted sources. Before opening a .qual file, scan it with antivirus software, verify that the file extension is expected, and avoid running unknown executable, installer, macro-enabled document, or script files.