Preamble is a fork of Attempt This Online (GitHub) which is © 2022 Patrick Reader and contributors. The software is used in accordance with its licence, which is GNU Affero General Public License 3.0, and is provided without warranty. is hosted by Dyalog Ltd at and its instance of the software repository is hosted at

The principal purpose of is to support other websites hosted by Dyalog Ltd. In order to access directly you must agree to the Terms of Use.

Privacy Policy

When you visit the, the following information is collected:

  • Your IP address. This is used to implement rate-limiting to prevent exhaustion of resources. A hashed version of your IP address may be stored for up to 1 month, and is never associated with any data except the amount of resources you use. Your IP address in an unhashed form may be stored for up to 1 year for security reasons.
  • Any data you submit in the Run form (code, input, etc.). These are only used to process your code execution request, and immediately deleted after execution has completed.

Any information you save on the Preferences page is stored locally in your browser and never shared with anyone

See also the general Dyalog Privacy Policy.

Terms of Use

"The Service" refers to the website at and all services provided at that URL. This does not include the Software itself, but only the instance of the Software made available at

Unless Dyalog Ltd grants you explicit written or electronic permission, you must not use the Service, except directly through the web page and as a result of your manual user interaction with it.

The Software includes an "API", which is a programmatic interface for interacting with the Service, but this is for use only by the Service internally, and by other websites hosted by Dyalog Ltd. You are not permitted to use the API otherwise.