In your GitBook organization, click on your docs site name in the sidebar, then Manage site, then Domain and redirects. Under ‘Subdirectory’, click Set up a subdirectory.
Enter the URL where you would like to host your docs. Then specify the subdirectory for docs access, e.g. tomatopy.pizza/docs, and click Configure.
Under Additional configuration, you will now see a proxy URL. You’ll use this in the next step when configuring your Vercel settings. Copy it to your clipboard.
2
Update your vercel.json
In your Vercel app, open your vercel.jsonfile (or create one in the root directory if you don't already have one). Then, add the following:
{"rewrites": [ {"source":"/docs","destination":"<INSERT YOUR PROXY URL FROM GITBOOK>" }, {"source":"/docs/:match*","destination":"<INSERT YOUR PROXY URL FROM GITBOOK>/:match*" } ]}
Be sure to update the URL on line 5 with the proxy URL you got from GitBook in the first step.
3
Re-deploy your app and try it out!
Re-deploy your Vercel app with the update configuration. This may take a few moments. Now, when visiting the URL, you should see your docs site!