Terms of use

Last updated: 1 October 2026

These terms apply to the Harkback browser extension and this website. By installing or using Harkback you agree to them. If you do not agree, do not use it.

1. The software

Harkback is open-source software released under the Apache License 2.0. The licence governs your right to copy, modify and redistribute the code. These terms cover your use of the extension itself.

2. Your model service and API keys

• Harkback works with a model service that you choose and configure. It sends the text of your request to that service. Your use of it is governed by that provider’s terms, privacy policy and pricing, not by Zestworks.
• You are responsible for your API keys, for any charges the provider makes, and for having the right to send the text you select to the provider you chose. Keys are stored unencrypted in your browser (see the privacy policy); use a key with a spending limit.
• Zestworks does not operate a model service and does not receive your requests, text or keys.

3. AI output can be wrong

Explanations are produced by a language model. They can be inaccurate, incomplete or out of date. Check anything that matters against the source. Harkback is a reading aid and not professional, legal, medical or financial advice.

4. Your content and your data

You keep all rights to the documents you read and to the records you create. Your records are stored on your own device; you are responsible for backing them up. Harkback saves a weekly backup file to your Downloads folder, but it cannot guarantee that data will never be lost.

5. Acceptable use

• Use Harkback only with content you are allowed to read and to send to your chosen model service. Mark confidential sources as sensitive and use a local model for them.
• Do not use it to break the law, to infringe others’ rights, or to bypass the access controls of a website or the terms of a model provider.
• Do not attempt to disrupt this website or misrepresent a modified version of the extension as the official one.

6. No warranty

Harkback is provided “as is” and “as available”, without warranties of any kind, whether express or implied, including fitness for a particular purpose, accuracy and non-infringement, to the extent the law allows.

7. Limitation of liability

To the extent the law allows, Zestworks and the contributors are not liable for indirect, incidental or consequential damages, for lost data or profits, or for charges made by a third-party model provider. Nothing in these terms limits liability that cannot be limited by law.

8. Changes and ending

We may update these terms and will change the date above when we do. Continued use after a change means you accept it. You can stop at any time by removing the extension. We may stop maintaining Harkback or this website.

9. Contact

Questions: open an issue at github.com/zestworks-io/harkback/issues.