This site is open-source under MIT License and is published through GitHub. You can check out the source code.
Disclaimer
Even though I tried my best to write the code of this site, and every function is tested with my YouTube account, I cannot guarantee that this site will work as expected. There can be potential bugs that damage your YouTube personal content. I am not responsible for your use of the function or information contained in or linked from this website. I am not responsible for any errors or omissions, or for the results obtained from the use of this website.
LET'S START!
Tutorial
If you've already followed this tutorial to create your Client ID, you can skip this tutorial.
If not, please follow this tutorial. The process might be complicated and annoying, but once you've set up, you won't need to do it next time.
YouTube Setup
Create YouTube Channel
If you already have a YouTube channel, you can skip this step.
If you don't have a YouTube channel, please create one. Otherwise, this tool won't work.
Click your account icon on the right-top side, and select "Create a channel". Then, follow the instruction to create your channel. You are good to proceed when YouTube tells you "Your channel has been created".
Tip: If you see "Your channel" instead of "Create a channel", it means you already have a YouTube channel, and you are good to proceed.
If this is your first time using it, the following screen will appear. Select your country, determine if you want Email updates, and continue after agreeing Terms of Service.
Click "CREATE PROJECT" at Dashboard.
Input a Project name and click "CREATE".
Enable YouTube API
Click "Library" on the left panel to enter API Library. Scroll down and click "YouTube Data API v3", then click "ENABLE".
Configure OAuth Consent Screen
Go to "OAuth consent screen" via Navigation menu.
Select "External", then click "CREATE".
Input an Application name, then click "Save". You can ignore other fields.
Create an OAuth Client Credential
Go to "Credentials" via Navigation menu.
Click "CREATE CREDENTIALS", then select "OAuth client ID".
Select "Web application" for Application type. Input a name for this credential. Click "ADD URI" in "Authorized JavaScript origins" section and input URI of this site: "https://sweeticelolly.github.io" (Not including quotation marks). Then, click "CREATE".
The page will tell you OAuth client created. Copy your Client ID. We will use it in the next step. Do NOT share your Client ID or Client Secret with others!
Authentication
Enter Your Credential
Copy the Client ID to the textbox below and click "Sign in".
If Google says "This app isn't verified", click "Advanced" and click "Go to sweeticelolly.github.io (unsafe)". If you are concerned about safety, you can check out the source code.
Allow this tool to perform operations to your YouTube playlists.
