• 1. Introduction
  • 2. Qt Commercial Licensing
  • 3. Qt Open source Licensing
  • 4. Online purchase and payments
  • 5. Extension purchases and contributions

1. Introduction

Qt is a commercial and open source licensed product developed by The Qt Company, together with the Qt project under the open source governance model.

In order to develop and distribute your product with Qt, you must adhere to obligations and definitions enforced by the licensing agreements.

1.1. Who actually owns and controls Qt?

Qt trademarks and most of the copyrights are fully owned and controlled by The Qt Company. The development work for Qt toolkit is done through the open source governed Qt project by The Qt Company R&D and external Qt contributors. The Qt project is an open ecosystem and infrastructure for developers and companies to contribute to Qt. All external contributions are licensed to the Qt company allowing re-licensing under both open source and commercial terms.

The Qt Company has a binding agreement with KDE Free Qt Foundation to ensure the availability of Qt under certain open source licenses for desktop and mobile platforms. The open source community and availability of Qt is an extremely important part of the whole value proposition of Qt, and something The Qt Company wants to commit to and drive forward.

1.2. What are the licensing options for Qt?

Starting from Qt 5.7, Qt is licensed under
 Commercial license
 LGPL3 open source license
 GPL2 or GPLv3 open source license

The general Qt toolkit, consisting of Qt Essential code libraries, the Qt add-on APIs, and the Qt Creator IDE are available dual-licensed for commercial and GPL licenses. Most of the Qt APIs are available also under LGPLv3 license but not all of the Qt Add-on modules.

In addition, the commercial Qt license includes additional tools and solutions for embedded development.

2. Commercial Qt licensing

2.1. Is there a difference between the commercial license bought online and the commercial license bought via a sales manager?

The features and functionality and license are the same. The difference is in the pricing and renewal policy (see questions 2.3 and 2.4)

2.2. What is a term license?

With a term license of Qt for Application Development or Qt for Device Creation, you pay a recurring fee during the time you develop with Qt and distribute the developed applications. You receive all updates and will be able to access online systems. After the term ends, you are no longer entitled to develop with Qt or further distribute the applications developed with Qt. Applications already distributed can be used, but not maintained.

2.3. What is a subscription license?

A subscription license is a recurring term based (see question 2.2) Qt for Application Development license sold through our web store. Please also see section 4.

2.4. Do I have to purchase a license for every developer in our team?

Yes. Each developer must have their own assigned Qt license. It’s not permitted to mix Qt commercial licenses with Qt LGPL licenses in one project.

2.5. Why and when do I need a license?

If you intend to develop software using the Qt framework, you will need a license (commercial or open source).

2.6. Can I develop with commercial Qt and install Qt creator to more than one of my computers?

Yes. You can install Qt and our development tools to as many computers as needed as long everyone using Qt has a valid commercial license. Our licenses are per individual, so all members of your project team using Qt need to have a license.

2.7. Can some developers in our team working on the same project use open-source version of Qt and some developers use Commercial version of Qt?

No. Each developer must have their own assigned Qt license. Mixing Qt commercial licenses with Qt open-source licenses in one project/product is not permitted.

2.8. Can I continue to use my license after it has expired?

No. It is not permitted to continue development if your license is not active. The rights to continue using the tools expire when the license term expires, or the subscription is cancelled.

2.9. Can I continue to distribute my application after my license has expired?

No. You are not permitted to further distribute your applications.

If you have unused Qt for Device Creation Distribution Licenses, you may continue distribute the application with your device for a period of 6 months. You are however not allowed to further develop or maintain the applications.

2.10. Can I continue to distribute my application with my device after my license has expired?

If you have unused Qt for Device Creation Distribution Licenses, you may continue distribute the application with your device for a period of 6 months. You are however not allowed to further develop or maintain the applications.

2.11. My license has expired; can I continue to get new versions or updates if I do not renew the license?

No. You must have an active license in order to get new versions/updates and receive support from The Qt Company.

2.12. I have licenses for the whole development team; can I renew it only for some members of my team?

All the developers that develop with Qt will need to have an active license. If the whole team develops with Qt, then they all need to have a valid license.

2.13. If I have started development of a project using the open source version (LGPL), can I later purchase a commercial version of Qt and move my code under that license?

This is not permitted without written consent from The Qt Company. If you have already started the development with an open-source version of Qt, please contact The Qt Company to resolve the issue. If you are unsure of which license or version to use when you start development, we recommend you contact The Qt Company to advise you on the best choice based on your development needs.

2.14. How long is the start for free / evaluation period?

The commercial evaluation term period is thirty (30) days. During that time, you can develop with Qt, but you are not allowed to distribute your applications before you purchase a paid license. After the free 30-day period, you need to either purchase a license or cease from using the free trial.

2.15. Do the Qt commercial licenses allow for easy publishing to the Apple App Store?

Yes. The Qt commercial licenses allow publishing to the Apple AppStore or other stores (including those that require static linking).

2.16. Which commercial Qt version grants rights to modify libraries?

All commercially licensed Qt versions allow modification of Qt libraries.

If you need technical support related to building Qt from source codes, at the minimum, Standard Support offered by The Qt Company is needed. Standard Support is included to our term licenses. If you need technical support for your modified Qt libraries, Premium Support offered by the Qt Company is required.

2.17. Do the commercial Qt license agreements grant the right to do static linking of Qt libraries with applications?


2.18. Can I distribute Qt binaries in conjunction with my desktop / mobile application?

Yes. Distribution of Qt libraries in binary form in conjunction with the developed application is allowed under the Qt for Application Development license agreements. A separate agreement is not needed. The platforms for which you have the right to distribute are listed in your license certificate (in your Qt Account).

2.19. Do I need to have a distribution agreement to develop an embedded device with Qt?

Yes. A distribution agreement explaining the terms for distributing the Qt libraries is included in your Qt License Agreement. When you create an embedded device you typically have ‘joint hardware and software distribution’, which is subject to a distribution fee, please contact us for more information.

2.20. What does a ‘joint hardware and software distribution’ mean in practice?

If you are making an embedded device with Qt, you most likely will have ‘joint hardware and software distribution’ as described in the Qt License Agreement. This is subject to a distribution fee, please contact us for more information.

2.21. Does Qt commercial licensing allow for source code distribution of Qt libraries or tools?

No, it does not. Qt libraries may be distributed in binary form only with the application.

2.22. Is there a way to add a platform to the online installer without an agreement with The Qt Company?

No. You must contact us. We are happy to add more platforms to the online installer.

2.23. Under the Qt commercial licenses, can I add new functionality and distribute Qt Creator?

No. Distribution of Qt Creator is prohibited without a separate agreement with The Qt Company.

3. Qt open source licensing

3.1. Why is Qt licensed also under an open source license?

We believe in the Free Software movement where using software comes with certain rights, but also certain obligations. Use of open source licensing gives users four primary degrees of freedom when using Qt applications or devices:

  • The freedom to run the program for any purpose
  • The freedom to study how the program works and adapt it to specific needs
  • The freedom to redistribute copies so you can help your neighbor
  • The freedom to improve the program and release your improvements to the public, so that the whole community benefits

The Free Software community has thrived because of these rules, but there are also developers who never intend to observe these rules, and thus should get a commercial license. The Qt Company exists to support both sets with the dual offering.

3.2. Why do you have an agreement with KDE about your licensing? What KDE is and what’s the history of Qt and KDE?

KDE is an international free software community, founded in 1996, producing an integrated set of cross-platform applications for desktop and mainly known for its Plasma Desktop environment, which is provided as the default work environment on many Linux distributions. KDE software is based on the Qt framework. In the early days of Qt, the KDE project and community was the biggest driving force in building the developer ecosystem around Qt.

In the very early days, Qt was already dual-licensed, but the source code was available under proprietary open source licenses. Compromises with KDE were sought to ensure that Qt would be available for their use under appropriate open source licensing even if Trolltech (the company that founded Qt) would be bought or go bankrupt. As a result, The KDE Free Qt Foundation was founded.

The KDE Free Qt Foundation is an organization with the purpose of securing the availability of the Qt toolkit for the development of Free Software and in particular for the development of KDE software. The Foundation was originally founded by Trolltech and the KDE e.V. (the legal non-profit organization behind KDE) in 1998 and it has a license agreement that ensures the availability of Qt under LGPLv3 and GPLv3 licenses for major desktop and mobile platforms. The license agreement has been updated couple of times over the years, mainly because of acquisitions around Qt or updates to licenses and platforms.

3.3. Who cares about the LGPL/GPL license version you are using

You, unless you are using Qt under a commercial license. Your customers and end users care! LGPL & GPL are copyleft licenses, which means that the license follows with your product to your end users and customers.

3.4. What is the consequence of not complying with the LGPL/GPL restrictions?

If software using these open source licensed libraries does not fully comply with the license obligations you will lose your license and related distribution rights.

3.5. Can I use the Community open source version to develop my commercial product?

It depends on how you license and distribute your product. The open source version of Qt is mainly distributed under the LGPL, version 3 and GPLv2/v3. You will need to fulfill the license obligations for these licenses when using Qt in your product.

3.6. What is the difference between LGPLv2.1 and LGPLv3?

LGPLv3 is the current version of the GNU Lesser General Public License. LGPLv2.1 is an older version and not recommended by the Free Software Foundation for new projects anymore. Both licenses have the same intention, namely to protect the freedom of users to use and modify the software licensed under LGPL.

LGPLv3 makes this intention very explicit. You have to provide means to the end user to install a modified version of the library licensed under LGPLv3 and run your software using that modified library. In practice, this for example refers to:

  • Tivoization – Explicitly not allowing creation of closed devices where the end user does not have the LGPL granted rights for the Qt open source libraries
  • DRM and hardware encryption – This cannot be used to circumvent these obligations
  • Software patent retaliation – Where all users of the software are granted licenses thus making software patent retaliation of any potentially patented software in the distributed software meaningless.

3.7. What are my obligations when using Qt under the LGPL?

If you are using Qt under the LGPLv3, there are a couple of obligations you will need to fulfill :

  • Firstly, you have to note that some Qt open source modules are not available for LGPLv3 license, for example Qt Charts, Qt Data Visualization and Qt Virtual Keyboard. These modules are only available under GPLv3 for open source usage.
  • You will need to deliver the complete source code of Qt (including all modifications you did or applied) to your users/customers. Alternatively you need to provide a written offer with instructions on how to get the source code. Please also note that this has to be under your control, so a link to the source code provided by the Qt Project or Qt Company is not sufficient.
  • The LGPL allows you to keep the source code of your application private as long as it is “work that uses” the library. Dynamic linking is usually recommended here.
  • The user of your application has to be able to re-link your application against a different or modified version of the Qt library. With LGPLv3 it is also explicitly stated that the user needs to be able to run the re-linked binary on it’s intended target device. It is your obligation to provide the user with all necessary tools to enable this process. For embedded devices, this includes making the full toolchain used to compile the library available to users. For parts licensed under LGPLv3 you are obliged to provide full instructions on how to install the modified library on the target device (this is not clearly stated with LGPLv2.1, although running the application against the modified version of the library clearly is the stated intention of the license).
  • The user of an application or device using LGPL licensed software has to be notified of their rights by providing a copy of the LGPL license to the end user and displaying a prominent notice about your usage of LGPL licensed software.

The above freedoms cannot in any way be restricted by other licensing terms. If an application is not fully following all the obligations as outlined above, it is not allowed to be distributed at all.

You will also need to make sure that you are not using any GPL licensed modules.

3.8. Do I need to worry about LGPL when using a commercially licensed version of Qt?

Usually, not. When using the commercially licensed version of Qt, we provide almost all of Qt under a commercial license terms.

A few modules in Qt, however, use code from the WebKit project licensed under LGPLv2.1. These modules are Qt Script, Qt WebKit and Qt WebEngine. So when using these modules, you will need to fulfill the license obligations of LGPLv2.1 (but not LGPLv3).

Please also note that you can avoid using Qt Script, as the Qt Qml module contains a fully functional JavaScript engine that can be used instead. This module is available under commercial licensing terms and doesn’t introduce a dependency to LGPL licensed code.

As a commercial license user, in practice, you only need to consider license obligations of LGPLv2.1, and only if you make use of Qt WebEngine or Qt WebKit .

3.9. I’m not sure if I’m in compliance with the licensing scheme. I am confused with the open source licensing. What should I do?

It is always recommended to contact a lawyer familiar with open source licenses for a full review of your project to determine whether you can fulfill all of the obligations of applicable open source licenses (LGPLv3/GPLv2/GPLv3). You can have a high level view of your options with the “Get Started with Qt” guide in our Qt.io/download –page. In case there is any doubt on whether the requirements of the open source licenses can be met in full, the commercial licensing option of Qt is often the best choice to avoid legal setbacks. We’re also happy to talk to you about your situation, but we aren’t in the position to provide any legal guidance.

3.10. How does commercial Qt licensing work? Do all my developers need to have a valid Qt license?

Please refer to section 2.

3.11. Can I mix code written with Open Source Qt and commercially licensed Qt?

No. Please refer to question 2.6.

If you want to migrate from open source Qt to a commercial license, you should contact us directly to discuss about your options in practice.

3.12. Is it possible to distribute applications developed with open source version of Qt via public application stores?

Each application store has their own unique terms and conditions, which may or may not be compatible with distributing applications under LGPL or GPL licenses.

The commercial license of Qt is compatible with the terms and conditions of all the leading application stores and thus typically the best choice for distributing a closed source application in various application stores.

3.13. I have started development of a product using the open source version of Qt, can I now purchase a commercial version of Qt and move my code under that license?

Products distributed under the commercial version of Qt must also be developed under the commercial version of Qt.

If you have already started the development with an open-source version of Qt and wish to move to a commercial license you need to have a written explicit permission from The Qt Company to facilitate this change. The Qt Company reserves the right to grant the permission at its own discretion.

If you are unsure of which license or version to use when you start development, we recommend you contact The Qt Company to advise you on the best choice based on your development needs.

3.14. Is it possible to use both LGPLv2.1 and LGPLv3 licensed libraries in the same application?

Yes, it is possible to use both LGPLv2.1 and LGPLv3 licensed libraries in the same application for example by having these as separate shared libraries. Doing this does not require changing license in either of the libraries, and it is possible to select a proprietary license for the application, if desired.

3.15. The GNU.org Compatibility Matrix suggests that I cannot combine LGPLv2.1 and LGPLv3?

If LGPLv2.1 code and LGPLv3 code are in different shared libraries, then they can be used in the same application, and you can license your application with a proprietary license / LGPLv2.1 / LGPLv3 as you wish.

4. Online purchases and payments

4.1. When will my credit card be charged?

Your credit card will be charged at purchase or after Start for Free period.

4.2. Can I cancel my subscription at any time?

You can cancel your subscription any time. However, note that when you cancel your subscription you will not be able to access Qt Creator and continue developing. Our tools are only available with an active subscription.

4.3. How do I cancel my subscription?

You can cancel your subscription from Qt Account Portal payments page.

4.4. How Do I Upgrade my Subscription from Monthly to Yearly Plan?

You can Upgrade Your plan as a self service via Qt Account Portal. Or contact us, and we’ll assist you.

4.5. How long is the Start for Free period?

Please refer to question 2.13.

4.6. Can I distribute my application/s during the Start for Free period?

Please refer to question 2.13.

4.7. How do I change my billing details?

You can change your billing details, for example credit card number, from Qt Account Portal payments page.

4.8. How do I change my subscription quantity?

You can modify your subscription from Qt Account Portal payments page.

4.9. Where can I see my current subscription status?

Please log in to your Qt Account.

4.10. What credit cards are accepted?

We accept Visa, MasterCard and American Express.

4.11. Why can’t I make purchase even if I have an accepted card?

It may be that the card issuer does not allow recurring payments or that internet payments are disabled. Please contact us if you have any problems with your payments.

4.12. Which currencies are supported?


4.13. How do you manage EU VAT (Value Added Tax)?

Companies in the EU will pay 0% if they provide a valid company VAT number that can be validated during the purchase process. In Finland ,companies pay 24% VAT, but they can claim the 24% tax fee via Finnish tax officials. Otherwise buyers must pay 24% VAT due to EU taxation. After purchasing, customers will receive a receipt to be presented to the tax authorities. Please note that the VAT number must be entered without spaces or punctuation and with country code.

Customers in non-EU countries don’t have to pay VAT.

4.14. Why does my VAT number not validate?

The EU-provided interface may be unreachable and therefore the VAT number cannot be validated.

The data in EU provided information may be incorrect and your number is not there or is incorrect. In this case it might be a good idea to contact your local tax authority.

You can claim the 24% tax fee via your own tax officials.

4.15. How is my order delivered?

Once your purchase is complete, you will receive a welcome email with information about your Qt Account. You can begin your download via the Qt Account where you will also be able to get updates and log support cases.

4.16. Can I use support services during the start-for free period?

Yes. Qt Support services are available via Qt Account Portal.

4.17. Is it secure to provide Credit Card details in Qt web shop?

Our payment system is PCI-DSS Level 1 compliant, and is recognized on the Visa Global Registry of Service Providers. We meet or exceed all industry-standard payment security practices to protect you and your customers.

4.18. What is PCI-DSS?

The Payment Card Industry Data Security Standard (PCI-DSS) provides a framework for developing a robust security process for credit card transactions. Any merchant or merchant service provider accepting, transmitting, and/or storing cardholder data must be PCI compliant.

4.19. Can I get Start for Free Package without entering my Credit Card details?

You can contact to Qt Sales via “Contact us” link

4.20. Why Personal details as well as Credit Card details are required with Start for free Subscription?

We are constantly looking at our product portfolio, and best possible options to serve our customers better. As a customer orientated company, your feedback would be very much appreciated.

5. Marketplace FAQ’s

5.1. What is Qt Marketplace?

Qt Marketplace offers a comprehensive collection of useful extensions for Qt to enhance functionality, development experience and development workflow. Marketplace is the number 1 place for the Qt community to find and share content for Qt.

5.2. Who can discover, download and purchase Qt Extensions from the Marketplace?

Everyone can browse Qt Marketplace and download open-source extensions. Everyone with a valid Qt Account can purchase Commercial Qt Extensions.

5.3. What kind of extensions can I expect to find from Qt Marketplace?

Marketplace provides developers with libraries for Qt framework, plug-ins for Qt Creator, and various tools, improving development productivity. The goal is to expand the extensions to include also other categories, such as Qt Design Studio bridges, design assets, services, and even physical products.

5.4. Who can contribute and publish new extensions in the Marketplace?

The Qt Company wants to create a platform, where any developer can share contributions to other developers - for free or as paid. Currently only VAT registered companies can publish paid extensions and individual developers can publish free extensions. To publish free extensions, you need Qt Account.

5.5. What kind of contributions are expected?

Tools, enhancing the SW lifecycle development, libraries extending functionality, Qt Creator plug-in, enhancing the development process.

5.6. What licenses can be used?

Based on your purpose, you can use OS or commercial licenses. Free extensions may use any commonly used open-source copyleft licenses, such as GPL-3.0-only, LGPL-2.1-or-later, MIT, Apache-2.0 or BSD-3-Clause. We should accept open-source licenses, not listed in SPDX license list https://spdx.org/licenses/. Paid extensions may use commercial license agreements that will be accepted by the developers during the purchase process. It is also possible to use dual licenses.

5.7. How do the users accept a custom EULA? 

Custom EULAs acceptance can be added to the purchase flow. Thus, the custom EULA is accepted before purchasing an extension.

5.8. How can a publisher track their own commercial purchases?

Qt Marketplace sends web hook and email notifications to publishers when an order related to their products is made. Publishers can also follow product orders from our Developer Portal if they have registered there.

5.9. What kind of payment models are supported?

Qt Marketplace supports both one-time and recurring payment models. Recurring payment is based on 1-year subscriptions. We are looking to create a model for trial (30 days) and buy payment method.

5.10. What do I need to provide for Qt to publish my extension in Qt Marketplace?

For the frontend we will require extension description (in a basic Markdown style) and extension manifest (JSON) that describes the extension properties. The use of images and videos is advised for better visualization of the extension and what it does. These files can be provided to us using this page. Publishers are expected to provide sufficient download, build, and install instructions for the end users to be able to easily use extensions.

5.11. What are the publisher guidelines?

The guidelines provide step by step instructions, what to do to contribute to Qt Marketplace. You can find the guidelines here.

5.12. How extensions are distributed?

Using common repos, like GitHub or publisher’s own repositories. Repo should be globally available with a sufficient download speed. After the purchase, the user will receive instruction to install publisher’s product in his/her Qt Online Installer and into their own Qt Project. Another option is that the user is redirected to product’s vendor portal where the installation process happens.

5.13. Where the extension repositories are hosted?

Publishers can pick up any repository they want. 

5.14. Can the extension be integrated with the Qt Installer Framework and what is needed for that?

Yes, we recommend this for the commercial extensions to provide a good user experience. After purchase the user will have components available among Qt components in the Qt Online Installer. The Qt Company will host the components and the publisher will provide updates. Please contact us to get the instructions. 

5.15. Who maintains extensions?

The publishers must maintain their extensions by themselves. Extension updates are submitted to The Qt Company.

5.16. Does it cost anything to contribute?

No. Publishing process is completely free for everyone.

5.17. What currency does Qt Marketplace use?

All the prices in Qt Marketplace are shown in US Dollars.

5.18. What kind of payment methods can I use in Qt Marketplace?

Qt Marketplace accepts all major debit and credit cards (Visa, Mastercard, Maestro, American Express) from customers in every country.

5.19. For paid content, how the revenue is shared and how is it delivered to the publisher?

Simple pricing model for paid extensions where Qt charges transaction fee only. The Qt Company charges the payment from the user and will remit the payment share to the Publisher.

5.20. Do I need to sign any kind of legal document to publish?

Publishers with paid extensions need to sign Publisher Agreement. The Qt Company will not publish paid extensions to the Qt Marketplace without signed Publisher Agreement. Free extensions do not need any agreement to be signed – instead it will be accepted while submitting the extension description and extension manifest through the submit link.

5.21. Who is reviewing my extension? 

All extensions will be reviewed by The Qt Company developers. Each proposed extension will be tested and verified. The Qt Company keeps the right to reject the extension without giving any reason for rejection.

5.22. Who to contact in case I have more questions? 

In case of questions and queries, do not hesitate to contact us by sending an email to publish.marketplace@qt.io. All feedback and improvement ideas are also most welcome.