Frequently Asked Questions
When using the RelTime method, can I add a calibration on the root node (crown node) of the whole tree?

This is not advisable because the relative rates between the outgroup [O] and ingroup [I] clades (which are both descendants of the root taxon [crown] of the tree) cannot be estimated in the absence of another taxon that can provide the divergence point between [O] and [I]. We do not recommend a mid-point rooting for this purpose when rates are varying, so RelTime does not provide a way to date or calibrate the whole-tree crown node. Even Bayesian methods do not know the relative rates between clades, but they do use the root calibration in their birth-and-death cladogenesis. So in our view, the best practice in RelTime is to find another outgroup such that the O+I clade becomes the ingroup.

Does MEGA run on new macOS computers with ARM-based M1 chips?

MEGA is currently NOT optimized to run on ARM-based M1 chips. Although MEGA has been run on these systems, performance is very poor and for large data MEGA will be unresponsive. We are currently developing a version of MEGA to run natively on the ARM architecture. In the meantime, macOS users can download the Windows or Linux version of MEGA and run it using virtualization software such as VMWare Fusion, Parallels, or Crossover.

Does the Log4j/Log4Shell vulnerability affect MEGA?

Log4Shell is a vulnerability found in the Log4j data logging package for the Java platform. MEGA is not developed using Java and does not use Log4j (or any other data logging software). The Log4Shell vulnerability is NOT known to affect MEGA. More information regarding the Log4Shell vulnerability can be found at and wikipedia/Log4Shell.

Which versions of MEGA are compatible with my macOS system?

Starting in macOS version 10.15 (Catalina), Apple has dropped support for 32-bit applications. For macOS 10.15 and all versions moving forward, MEGAX 10.1.4 and later must be used. However, earlier versions of MEGA can be ran on macOS 10.15 and later by using a Windows version of MEGA with virtualization software such as VMWareFusion.

For the following versions of macOS it is recommended to use MEGAX 10.0.0 or later:

  • macOS 10.14 (Mojave)
  • macOS 10.13 (High Sierra)

MEGAX has not been tested on the following versions of macOS. Although MEGA7 has been tested on these versions, support is no longer provided for MEGA7:

  • macOS 10.12 (Sierra)
  • macOS 10.11 (El Capitan)
  • macOS 10.10 (Yosemite)
  • macOS 10.9 (Mavericks)

If there is not a version of MEGA listed here that is compatible with your macOS system, any of the Windows versions of MEGA can be ran on macOS by using virtualization software such as VMWareFusion.

I my upgraded macOS system to version 10.15 (Catalina) or newer and now MEGA does not run. What should I do?

Starting in version 10.1.4, MEGAX has been updated to meet the more stringent requirements for running 3rd party applications that were introduced in macOS 10.15 (Catalina). You should download and install MEGAX 10.1.4 or later.

How do I use MEGA-CC?

For basic instructions on using MEGA-CC, see the MEGA-CC-Quick-Start-Tutorial

Do I need to purchase a license to use MEGA?

No. MEGA is provided free of charge for all research and educational purposes. However, it is not permissible to redistribute MEGA in any form to other users. We require that all users download their own copy of MEGA from our website directly. MEGA is protected by all applicable copyright laws.

Can I install MEGA in a classroom/lab using a script?

Because MEGA includes many statistical methods for the study of molecular evolution in an interactive framework, it is instructive for classroom teaching. If you are interested in using MEGA in the classroom/lab, there are no restrictions. Your students may download a copy from the website or you may install copies on multiple computers in a common computing area. However, if you want to use MEGA in any other form, please contact the authors by e-mail ( ).

If you are using MEGA in classroom teaching, please send us the following information by e-mail for our records ( ).

  1. Your name, position and institution
  2. Course number and title
  3. Number of students
  4. Course semester and year

To perform a silent install of MEGA on MS Windows computers, call the installer executable with the /SILENT and /VERYSILENT switches. For example:


Then MEGA will be installed using the default options. The install will also probably need to be run with admin privileges so that the User Account prompt is not shown.

To perform a silent install of MEGA X on Linux systems, refer to the documentation for the package management software that you are using (probably either dpkg or rpm).

I am not a member of an educational institution. May I still use MEGA?

Yes, MEGA is provided free of charge for commercial institutions as well. However, it is not permissible to redistribute MEGA in any form to other users. We require that all users download their own copy of MEGA from our website directly. MEGA is protected by all applicable copyright laws.

How do I cite MEGA?

Citation for MEGA 11:
MEGA 11: Molecular Evolutionary Genetics Analysis version 11.
Tamura K, Stecher G, and Kumar S (2021)
Molecular Biology and Evolution 38: 3022-3027.
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Citation for MEGA X:
MEGA X Molecular Evolutionary Genetics Analysis across computing platforms.
Kumar S, Stecher G, Li M, Knyaz C, and Tamura K (2018)
Molecular Biology and Evolution 35: 1547-1549.
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If using MEGA X on macOS, please cite this paper as well:
Molecular Evolutionary Genetics Analysis (MEGA) for macOS.
Stecher G, Tamura K, and Kumar S (2020)
Molecular Biology and Evolution 37: 1237-1239.
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Citation for MEGA 7:
MEGA7: Molecular Evolutionary Genetics Analysis Version 7.0 for bigger datasets.
Kumar S, Stecher G, and Tamura K (2016)
Molecular Biology and Evolution 33(7):1870-1874.
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Citation for MEGA 6:
MEGA6: Molecular Evolutionary Genetics Analysis Version 6.0.
Tamura K, Stecher G, Peterson D, Filipski A, and Kumar S (2013)
Molecular Biology and Evolution 30: 2725-2729.
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Citation for MEGA 5:
MEGA5: Molecular Evolutionary Genetics Analysis using Maximum Likelihood, Evolutionary Distance, and Maximum Parsimony Methods.
Tamura K, Peterson D, Peterson N, Stecher G, Nei M, and Kumar S (2011)
Molecular Biology and Evolution 28: 2731-2739.
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Citation for MEGA-CC:
MEGA-CC: Computing Core of Molecular Evolutionary Genetics Analysis Program for Automated and Iterative Data Analysis.
Kumar S, Stecher G, Peterson D, and Tamura K (2012)
Bioinformatics 28:2685-2686.
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Citation for MEGA 4:
MEGA4: Molecular Evolutionary Genetics Analysis (MEGA) software version 4.0.
Tamura K, Dudley J, Nei M & Kumar S (2007)
Molecular Biology and Evolution 24: 1596-1599.
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I have an idea on how to improve MEGA. How can I contact the authors?

The authors of MEGA appreciate all forms of user suggestions and feedback. In order to properly address each suggestion, we encourage the use of the Suggestion Box form found in the Support/Feedback section of the MEGA website.

I discovered a software bug in MEGA. What should I do?

Please report the bug to the MEGA development team immediately using the Bug Report submission form on the MEGA website. User-submitted bug reports are invaluable to the MEGA development team. Due to limited resources, you may not receive a reply to your bug report immediately, but we can assure you that each bug report will be addressed and responded to as soon as possible by a member of the MEGA development team.

What is the X11 program that opens with older versions of MEGA on MacOS X?

X11 is a program that comes with MacOS X and is essential for displaying the Wine and Wineskin versions of MEGA (MEGA7 and earlier) on the Mac. If you close X11 MEGA will close as well.

Can I use MEGA in a shared (Terminal Server) environment?

Yes, starting in version 4, we have built support for a multi-user environment, which will allow each user of the same computer to keep his/her customized settings, including file locations, window sizes, choice of genetic code table, and previously-used analysis options. This feature will facilitate educational and laboratory usage where a single computer is often shared by multiple users.

MEGA comes up when I click on the file with extension FAS. How can I disable this?

Simply right-click on the file with the FAS extension to navigate to the properties item. You can then select the program that you wish to associate with that extension.

How can I use MEGA with the error message "no common sites found for computing distance"?

You must identify which taxa have no common sites with others, and then remove them in order to continue your computing. Please follow this procedure to check the number of common sites between taxa:

  1. Click Distances|Compute pairwise from the main menu
  2. In the Analysis Preference window, select " L: No. of Valid Common Sites" from drop down for the option "Substitutions to Include"
  3. Click "compute" button to get a matrix.

The number in the matrix indicates the number of common sites between sequences that are available for analysis. When this number is zero, there are no common sites. To get around this problem, you may want to eliminate some sequences. In addition, the use of the "Pairwise-Deletion" option for handling alignment gaps and missing data may also be employed.

I use MEGA on a network drive. When the network connection is unavailable/broken, why does MEGA display an error message after I try to open a file or close the application?

MEGA can only be used over the network if the directory where MEGA EXE is stored is available for reading (not writing). The user does not need writing privileges on the network. If your bug report indicates that you have an unreliable network connection, then it will be impossible to use MEGA reliably.

MEGA also writes temporary files in the User's Home Directory. This local directory will often be housed on the local computer (in which MEGA EXE is running), and it will always be available. A completely network-based use of MEGA (including User's Home Directory) will cause problems due the non-reliability of network connections (and thus temporary and setup files).

How do I prevent the "MEGA Update Available" message from showing up ever?

Go to your MEGA appdata directory eg. %appdata%/MEGAX_XXXXXXX\, then /Private/Ini/ and edit the ignore_updates.ini file. Change the 0 to a 1 .

If you are running the MEGA exe from a remote computer this should work too.

I'm converting a file to MEGA format using the built in converter, but get an error message/invalid result/crash. Whats wrong?

Many programs which write out their own files don't stick to the official file format format. This means MEGA has to be able to handle lots of slightly different implementations of the same file format.

We try our best to be able to convert all file formats but including formats which don't exactly match their format.

Check the file you want to convert, and make sure there are NO spaces in the taxa/sequence names as this often can cause issues.

Why can't I view branch lengths in a bootstrap consensus tree?

MEGA does not compute or provide branch lengths for consensus tree, as they generally contain multi-furcations due to the partition frequency cut-offs. Estimates of branch lengths in these cases are not correct, as the collapsed partitions have non-zero lengths in reality but they are not statistically resolved (i.e., lack of significance by bootstrap method) so they are drawn accordingly on the screen.

Only the branching pattern from the bootstrap tree should be viewed as is, and the branch lengths should be what you see in the "Original Tree" tab.

Can I download the MEGA source code?

The source code for the computational core of MEGA is released under the terms of the GNU General Public Licens and is freely available from GitHub.

How can I restore MEGA to its default settings?

If you experience a problem with MEGA that is related to saved settings (such as weird formatting or problems with the decimal separator), you may be able to resolve the problem by restoring MEGA to its default settings:

  1. Close MEGA if it is open. In a file system explorer window navigate to the folder where MEGA keeps its settings files and delete the folder that contains the settings files:
    • On Windows: open a File Explorer window and type %localappdata% in the address bar and press enter button on your keyboard. Navigate to your MEGA\MEGA_buildnumber\Private folder and delete the Ini folder that is there.
    • On Linux: navigate to your ~/.config/MEGA/MEGA_buildnumber/Private directory and delete the Ini directory
    • On macOS
      • For MEGA12 and later, right-click MEGA in your Applications folder and select Show Package Contents. Navigate to Contents/Resources/Private and delete the Ini folder
      • For MEGA11 and earlier, navigate to your ~/.config/MEGA/MEGA_buildnumber/Private folder and delete the Ini folder
In the above, the actual path to your Ini directory will depend on the version of MEGA you are using. The path will look something like %localappdata%\MEGA11\MEGA_11220624-x86_64\Private\Ini or ~/.config/MEGA11/MEGA11_11220624-x86_64/Private/Ini