| CARVIEW |
Latest version: 7.4.1 (November 2025)
News
30 November 2025: Regina 7.4.1 is out! This is a service release, and includes an important bugfix regarding triangulated boundary components. Read about the changes, or just go ahead and download it.
29 August 2025: Regina 7.4 is out! This is a big one. Read all about what's new here.
What is Regina?
Regina is a software package for low-dimensional topologists, with a focus on 3-manifold and 4-manifold triangulations, knots and links, normal surfaces, and angle structures.For 3-manifolds, it includes high-level tasks such as 3-sphere and unknot recognition, connected sum decomposition and Hakenness testing, comes with a rich database of census manifolds, and incorporates the SnapPea kernel for working with hyperbolic manifolds. For 4-manifolds, it offers several combinatorial and algebraic tools, as well as support for normal hypersurfaces. For knots and links, Regina can perform combinatorial manipulation, compute knot polynomials, handle virtual knots and links, and work with several import/export formats.
Regina comes with a full graphical user interface, as well as Python bindings and a low-level C++ programming interface.
See the users' handbook for a detailed list of features.
Screenshots
Click on each thumbnail below for a full-sized version of the screenshot.
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| Studying 3-manifold triangulations |
Normal surfaces and angle structures |
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| Knots and links |
In-built Python scripting |
Download
The following downloads are available:
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All direct downloads come with SHA-1 checksums and SHA-256 checksums, signed with Ben Burton's GPG key.
If you encounter any problems when you run Regina, you can check the
troubleshooting page to
see if your problem is discussed there. You also most welcome
to contact us for help.
Mac
Regina runs natively on both Intel and Apple Silicon machines.
It ships with its own copy of Python 3, which is bundled inside
Regina's macOS app.
You can download Regina either from this website, or via the App Store (for free of course). Not sure which? Start with the App Store version (but read below).
macOS version Website download App Store Tahoe (26)
Sequoia (15)
Sonoma (14)Download here
There are some minor differences between the website and App Store versions. The App Store version:
- means that macOS will notify you of upgrades;
- is sandboxed for extra security, which limits file access through Python and the command-line tools (see below).
Sandboxing is a security measure that comes with all App Store downloads: it ensures that apps only access files that you explicitly choose through the graphical file dialogs (Open, Save, etc.). For Regina, this means that when you open a Python console or run command-line tools (regina-python, regfiledump, etc.), the only personal files you can access are those in your Downloads folder. You can still access world-readable files, such as those in your Applications folder.
Regarding security:
- The website download is cryptographically signed with Ben Burton's Apple developer certificate, and has been pre-screened (notarised) by Apple. macOS will verify all of this when you first try to run Regina. You should see a message like “Regina is an app downloaded from the internet… Apple checked it for malicious software and none was detected.”.
- The App Store version has been screened by both machines and humans at Apple, and has a chain of cryptographic signatures that certify this. These signatures will be verified when you install Regina via the App Store.
Windows
Regina on Windows uses a standard point-and-click installer.Regina now only supports 64-bit Windows, and only on Intel/AMD64 chipsets (i.e., the x64 architecture). Most modern Windows installations are of this type, and this is almost certainly the version that you want.
If your machine has an ARM64 chipset (e.g., you have a Mac with Apple Silicon), you will need to run Regina under a different operating system (e.g., macOS or GNU/Linux).
Windows version Architectures Installer Windows 11
Windows 10x64 Download
Regarding security:
- When downloading or running the installer you may see a security warning, such as “Microsoft Defender SmartScreen prevented an unrecognized app from starting…”, or a message that “Microsoft Defender SmartScreen couldn't verify if this file is safe…”. This is because Microsoft has not added Regina to its database of known applications. Click More info or look for a drop-down box with more options, and you should be able to run the installer anyway.
- If you wish to verify the integrity of the download, you can compare checksums against the expected SHA-1 checksums and SHA-256 checksums, which are cryptographically signed with Ben Burton's GPG key.
GNU/Linux
You can download ready-made packages for several GNU/Linux distributions through Regina's online package repositorites. These repositories integrate with your native package manager (apt, dnf/yum, zypper, etc.) to help you keep Regina up-to-date automatically.For instructions on setting up Regina's package repositories, click on the Install link for your system in the table below.
Regina's GNU/Linux packages are named regina-normal (to avoid conflicting with the other Regina).
Distribution Versions Architectures Instructions Arch Linux Rolling release x86_64 Install Debian 13.x (trixie)
12.x (bookworm)amd64
arm64
i386 (bookworm only)Install unstable (sid) Everything Fedora 43
42
41aarch64
x86_64Install openSUSE Leap 16.0
Leap 15.6aarch64
x86_64Install Ubuntu 25.10 (questing)
25.04 (plucky)
24.04 LTS (noble)amd64
arm64Install
Architectures:
- You do not need to know what architecture you have; the online repositories will work this out for you automatically.
- For reference, amd64/x86_64 refers to 64-bit Intel machines, arm64/aarch64 refers to 64-bit ARM machines (including Apple Silicon), and i386 refers to very old 32-bit Intel machines. Together these cover almost any typical desktop or laptop nowadays.
- If you have a more exotic chipset that is not in the table above, you can try downloading the regina-normal source package (which is provided for all distributions above except for Arch Linux), and use this to build a binary package yourself (e.g., using debuild or rpmbuild). Alternatively, if you really want a ready-made binary package, you could try the Debian unstable packages, which are built for every architecture in Debian.
For older versions of GNU/Linux:
- If your distribution is in the table above but your version is too old, then your version of GNU/Linux may have passed its end-of-life. This is a security risk, since most distributions do not provide security updates for old (end-of-life) versions. You should seriously consider upgrading your machine.
For newer versions of GNU/Linux:
- If your distribution is in the table above but your version is too new, then drop Ben an email and he should be able to upload a package for you. Otherwise you can always build from source (see below).
For other GNU/Linux distributions:
- If you are using some other distribution (e.g., RedHat, Slackware, …), then you will need to build Regina from source.
Regarding security:
- All of Regina's GNU/Linux repositories use cryptographic signatures to verify the integrity of the packages. Follow the appropriate Install link above for details.
PyPI / SageMath
Marc Culler, Nathan Dunfield and Matthias Goerner have kindly prepared a PyPI package that allows Regina to be used with SageMath. This includes the Python interface to Regina's mathematical engine, but does not include Regina's graphical user interface or command-line tools.
System Instructions PyPI Install
Of course, whilst the packages are written to work with any modern version
of SageMath, your experiences might vary (particular with an older SageMath
and/or operating system). Follow the instructions link above for details.
iPad
The iPad app is currently in hiatus. It has not been updated since before the
pandemic began, and there is a lot of rewriting to do.
Hopefully Ben will have time to do this some time during 2025.
Source code
For other systems not listed above, you will need to build Regina from its source code.
You can download the source code here.
Please see the separate page on building Regina for instructions on how to build Regina and what libraries and tools you will need to have installed.
Documentation
Regina comes with rich documentation for both users and developers.Users' Handbook
The Regina Handbook is full of screenshots, and walks you through the different things that Regina can do.You can read the handbook from within Regina by selecting Help → Regina Handbook from the menu. You can also read it here online.
Python/C++ API Documentation
If you are doing Python scripting or C++ programming with Regina, there is extensive API documentation for Regina's mathematical engine. This describes the various objects, classes and functions that Regina makes available to you.You can read the API documentation by:
- selecting Help → Python API Reference from the menu;
- reading it here online;
- getting inline help directly within Python via docstrings (but please see the handbook for the limits of what these docstrings can and cannot provide).
What's new in version 7.4.1?
Regina 7.4.1
This is a service release to fix some important bugs, and to support additional build environments. In particular:
- Fixes a serious (and very old) bug that occurred when triangulating a real boundary component. In short, the new triangulation of the original boundary component could have had inconsistencies in the labelling of its own lower-dimensional faces. Ideal boundaries were not affected. For a detailed discussion of how this might have affected you, see the bugs page.
- Fixes a bug in Katie's quadricolour search routine, which would cause a segfault for certain inputs.
- Adds a few missing Python bindings for triangulations in higher dimensions.
Regina 7.4
In case you missed it, Regina 7.4 (August 2025) added many new features:
- Now supports virtual knots and links, with new invariants such as odd writhe, arrow polynomials, affine index polynomials, and extended groups.
- Several new constructions, such as Whitehead doubles over links, doubling triangulations over their boundaries, and many new out-of-the-box example triangulations and links.
- Several new operations on triangulations and link diagrams, including improving treewidth, truncating individual vertices in 3-D, and more elementary moves in more dimensions.
- New invariants and properties for link diagrams, including Alexander polynomials, Seifert circles, and connected diagram components.
- Significantly better simplification for 4-D triangulations, including Rhuaidi Burke's “up-side-down” simplification heuristics.
- Text codes for link diagrams now include signed Gauss codes, plus an extension of Regina's knot signatures to multiple-component links.
- You can now lock top-dimensional simplices and/or their facets in a triangulation, to prevent these from being modified during operations such as simplification or elementary moves. Locks are also encoded as part of the isomorphism signature.
- Gave the graphical user interface a general glow-up, and added initial support for multithreaded computations.
- The tool DGT is now called Katie, and can now work with 1-handles (thanks again to Rhuaidi Burke).
- New command-line tool regina-helper, which can do things like create Makefiles and run the test suite.
- Fixes an occasional problem where the “try harder” option for simplifying triangulations could make the user interface crash.
- Many, many other smaller features and optimisations.
Also, the build requirements have changed: Regina now uses C++20 (not C++17), the GUI now requires Qt 6.x, the API docs now require Doxygen ≥ 1.9.2, and you no longer need Jansson, Popt or CppUnit.
Release announcements
The old SourceForge mailing lists have now been decommissioned.To be notified of new releases, you can instead subscribe to Regina's releases directly on GitHub. See the Regina Handbook for details.
License and citation
The primary developers of Regina are Benjamin Burton, Ryan Budney, and William Pettersson.Many others have been of assistance with this project, be it through time, knowledge, testing or code. Please see the full list of acknowledgements in the users' handbook.
Citation
If you find Regina useful in your research, please consider citing it as you would any other paper that you use. A suggested form of reference is:Benjamin A. Burton, Ryan Budney, William Pettersson, et al.,Or, in BibTeX:
Regina: Software for low-dimensional topology,
https://regina-normal.github.io/, 1999–2025.
@misc{regina,
author = {Benjamin A. Burton and Ryan Budney and William Pettersson and others},
title = {Regina: Software for low-dimensional topology},
howpublished = {{\tt https://\allowbreak regina-normal.\allowbreak github.\allowbreak io/}},
year = {1999--2025}}
Copying and modification
Regina is copyright © 1999–2025, The Regina development team.This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.
Some of this code comes with additional permissions, which allow it to be distributed through online repositories such as Apple's App Store or Google Play. See the full license in the users' handbook for details.
This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with this program; if not, see https://www.gnu.org/licenses/.
Detailed license
Regina includes portions of external software for specialised tasks (such as code from SnapPea and SnapPy for some geometric calculations, and code from Normaliz for computing Hilbert bases).For complete license details, including the full GNU General Public License and information on external software that Regina uses, see the full license in the users' handbook.
Contact
If you have any suggestions, problems, bugs, wishes, frustrations or otherwise miscellaneous comments, we would really love to hear them. This program is permanently under development and we would like to know what people want out of it.If you have written your own extensions that you think could be worth putting in the main release, please do write and let us know.
Even if you have no comments to make, it's always nice to hear from people using Regina, even if it's just to say hi. We're always interested to hear how this software is being used.
You can contact us by email: our websites are linked to our names in the author list above.