CodiMD Book mode is a Chrome extension that provides a sidebar similar to HackMD's book mode. Developed by, this extension is designed to enhance the functionality of CodiMD for personal use. It is available for free and falls under the category of Browsers, specifically Add-ons & Tools.

Before using the extension, it is important to note that it is not developed by the HackMD team and may have undiscovered defects. Users are advised to exercise caution before using it. The extension requires certain permissions, such as webRequest and declarativeNetRequest, to read and modify security headers related to iframes.

One notable difference between this extension and HackMD is that links will be opened in a new tab. Additionally, the extension adds the [target=_blank] attribute to links and supports cross-origin functionality.

Please note that the extension will only enable book mode if the hostname contains "hackmd" or "codimd". If you are hosting CodiMD without a domain name, this extension may not be suitable for your use.

Overall, CodiMD Book mode is a helpful extension for users of CodiMD who want to enhance their note-taking experience with a sidebar similar to HackMD's book mode.