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The problem content on the site is licensed under a Creative Commons (CC) Licence:

Attribution-NonCommercial-ShareAlike 4.0 International (CC BY-NC-SA 4.0)
Creative Commons License

You can read a Summary of the Licence, but that is not a substitute for the Full Licence Legal Code.

All other content, including the statistics made available to members, is subject to standard copyright laws and may not be published or shared elsewhere.

Can I freely make use of the problems elsewhere?

Yes! As long as you operate within the bounds of the CC Licence it is not only granted but encouraged for the problem content to be shared and used freely for non-profit making purposes. But please read on...

All of the problems have been gathered from a variety of sources: some are based on interesting sub-results of larger mathematical theorems, others are variations of classic problems, the rest are believed to be original. The primary mission of Project Euler is to present high quality problems for the purpose of both encouraging learning and to challenge in an enjoyable context.


Are there any restrictions?

Considerable effort and thought has been put into the design of each problem, and in that sense all material is new and original. For this reason problems must not be used for commercial purposes.


Do I need to show attribution?

Under the CC Licence it is a requirement, but it should also be a matter of courtesy. You are entirely at liberty to use the material as it is or adapt it. If you choose to use the content as it appears on the website, then you could say something like, "The following problem is taken from Project Euler." If you modify the problem then you could say something like, "The following problem was inspired by Problem xxx at Project Euler." But please note that the terms of the licence require that any derivative work will be subject to the same licence.


Do you have a preferred way of linking directly to a particular problem?

You can link directly to Problem xxx with the following URI:

https://projecteuler.net/problem=xxx

Creative Commons Licence
This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.