It may or may not be inaccessible, depending on how you transfer. If you are using the nameservers of your registrar, there are possibilities that your website may go down for some time. If you use third-party nameservers, such as Cloudflare or he.net, the probability of going down will be very low.
Here are steps that you can follow if you do not want downtime:
- If you use your registrar's nameservers, it's time to change your DNS provider. Use any third party (Cloudflare or he.net) as your DNS provider. Wait for at least 24 hours for the DNS propagation.
- You can skip the first step if you are already using a third-party DNS provider.
- Initiate the domain transfer from the old provider to the new provider.
- Once your domain is available at your new provider's panel, change the nameservers to the third-party nameservers.
That's it. You are all set, and hopefully, there will be no downtime.