YouTube Playlist Length LogoYTP Length
Back to Blogs

The Secret Language of YouTube URLs: Decoding Playlist IDs

By Gokul·June 5, 2026
Cover image for: The Secret Language of YouTube URLs: Decoding Playlist IDs

If you look closely at a YouTube URL, you will notice a string of characters at the end. At first glance, it might look like random gibberish. But when I was building my tool, YTP Length, to calculate playlist durations, I had to work with thousands of these links. That is when I realized that these strings are actually highly structured, Base64-encoded identifiers.

Understanding how YouTube formats its playlist IDs gives you a lot of control as a developer, creator, or even a curious viewer. By simply looking at the first few letters of a playlist link, you can immediately tell what type of playlist it is - whether it was made by a user, generated by an algorithm, or linked directly to a channel's hidden backend.

Here is a simple guide to decoding YouTube playlist prefixes, how they are built, and how you can use them.

1. The Anatomy of a YouTube ID

Before looking at playlists, let's understand how these IDs are created. YouTube uses a modified Base64 character set. This means any ID you see is built using:

  • Uppercase letters (A-Z)
  • Lowercase letters (a-z)
  • Numbers (0-9)
  • Hyphens (-)
  • Underscores (_)

Because the system relies strictly on these characters, any other symbols you see in a URL (like &, =, or ?) are just routing parameters used by the browser, not part of the actual ID itself.

2. Channel-Derived Playlists (The System Hacks)

Every YouTube channel has a unique, 24-character ID starting with the prefix UC (which stands for User Channel). YouTube's system is built so that you can swap out those first two letters - or prepend a code to the channel's 22-character suffix - to instantly find special, system-generated playlists for that exact channel.

To make this hands-on, we will use MrBeast's official channel as our example:

  • Channel ID: UCX6OQ3DkcsbYNE6H8uQQuVA
  • Unique Suffix: X6OQ3DkcsbYNE6H8uQQuVA (extracted by removing the UC prefix at the start)

Here is the complete breakdown of the hidden system playlists you can generate from a channel ID, along with live links using MrBeast's suffix so you can test them out immediately in a new tab:

Upload Lists: All, Video-Only, Shorts, and Live Streams

Depending on what content type you want to target, YouTube provides different prefixes for a channel's uploads:

  • UU (All Uploads):
    • How to build: Replace UC with UU (e.g., UU1234567890abcdefghijklmn).
    • What it is: A playlist of everything that channel has ever published, containing long-form videos, Shorts, and past live streams, ordered chronologically.
    • My Experience: When I was building YTP Length, using UU was the fastest way to fetch all content from a channel. Many web developers use this to auto-embed a creator's latest upload on their personal websites.
    • Try it (MrBeast): MrBeast's Uploads Playlist (UUX6OQ3DkcsbYNE6H8uQQuVA) - plays all uploads chronologically.
  • UULF (Public Videos Only):
    • How to build: Replace UC with UULF (e.g., UULF1234567890abcdefghijklmn).
    • What it is: A playlist containing only standard, long-form videos. It automatically excludes Shorts and live streams.
    • Try it (MrBeast): MrBeast's Long-form Videos Only (UULFX6OQ3DkcsbYNE6H8uQQuVA) - plays long-form content only.
  • UUSH (Shorts Only):
  • UULV (Live Streams Only):
    • How to build: Replace UC with UULV (e.g., UULV1234567890abcdefghijklmn).
    • What it is: A chronological playlist containing only the channel's past and currently active live stream broadcasts.
    • Try it (MrBeast): MrBeast's Live Streams (UULVX6OQ3DkcsbYNE6H8uQQuVA) - plays past live streams.

Popularity Filters: Trending & Most-Viewed Feeds

You can also access the channel's top-performing content directly via system playlists:

Personal & Legacy Feeds

  • LL (Liked List):
    • How to build: Replace UC with LL.
    • What it is: A system list of every video the channel owner has liked. By default, these lists are private today, but authenticated integrations can use them to sync favorites across devices.
    • Try it (MrBeast): MrBeast's Liked List (LLX6OQ3DkcsbYNE6H8uQQuVA) - private/inaccessible unless logged in as MrBeast.
  • FL (Favorites List):

Premium & Members-Only Feeds

For channels with active memberships enabled, you can even target private video directories:

3. Standard User Playlists (PL)

This is the prefix you will see most often when using my tool or browsing YouTube.

  • Length: Typically 18 or 34 characters.
  • What it is: When you log into YouTube and click "Create Playlist" to group your favorite videos, the system generates a standalone ID starting with PL.
  • Details: Older playlists usually have 18 characters, while modern ones use 34 characters to handle the massive growth of the platform.
  • Why it matters: Content creators use these PL links to organize courses, music collections, or video series. It ensures viewers can watch videos in the exact sequence the creator planned.

4. Algorithmic and YouTube Music Lists

YouTube's recommendation engine and YouTube Music use their own unique playlist prefixes, which are designed for continuous, infinite playback.

RD (Radio / Mix)

  • Length: Usually 13 characters, but can vary.
  • What it is: An auto-generated, endless playlist (often called a "Mix" or "Radio"). It usually combines the RD prefix with an 11-character video ID.
  • Use Case: If you run a cafe or store, casting an RD link based on a single song lets YouTube stream similar music endlessly without you needing to manage a playlist.

OLAK5uy_ (Official Album)

  • Length: 44 characters.
  • What it is: The prefix used by YouTube Music to group official audio tracks into an album layout.
  • Why it matters: It ensures that music plays in the artist's original track order and that streaming royalties are correctly tracked.

RDCLAK5uy_ (Curated Chart)

  • Length: 44 characters.
  • What it is: Used for YouTube Music's editorial charts (like "Top 50 Pop" or "Viral Hits").
  • Use Case: These playlists update automatically on the backend, making them perfect for event DJs or fitness centers that want to stream current hits without manual updates.

5. Premium and Utility Endpoints

YouTube reserves a few specific prefixes for utility actions and protected media.

WL (Watch Later)

  • Length: Exactly 2 characters.
  • What it is: A universal, static endpoint that redirects to your personal, private "Watch Later" queue.
  • Use Case: App developers use the WL ID to build browser extensions. With a single click, users can send a video from a random blog straight to their TV's Watch Later queue.

LM (Liked Music)

  • Length: Exactly 2 characters.
  • What it is: The system-assigned playlist ID for your "Liked Music" (or Liked Songs) collection, specifically in the YouTube Music ecosystem.
  • Details: While the LL playlist lists all videos you have liked across the entire YouTube site, the LM playlist is dynamically filtered specifically for music tracks and songs.
  • Use Case: Like WL, LM is a static ID. You can go to https://music.youtube.com/playlist?list=LM to load your liked songs immediately. Third-party music sync tools use this ID to identify and migrate users' liked songs.

EL (Educational / Premium)

  • Length: Usually 13 characters.
  • What it is: The identifier for DRM-protected content, such as purchased movies, premium TV shows, or paid educational courses.
  • Why it matters: If you are building a media integration (like for Plex), this ID helps you separate free, public videos from paid, copyright-protected movies.

Summary: A Quick Cheat Sheet

Here is a quick summary table of what we covered:

PrefixType of PlaylistTypical LengthHands-On Link (New Tab)
PLStandard User Playlist18 or 34 charsTry PL Link
UUAll Uploads (Videos + Shorts + Live)24 charsTry UU Link
UULFVideos Only26 charsTry UULF Link
UUSHShorts Only26 charsTry UUSH Link
UULVLive Streams Only26 charsTry UULV Link
UULPPopular Videos26 charsTry UULP Link
UUPSPopular Shorts26 charsTry UUPS Link
UUPVPopular Live Streams26 charsTry UUPV Link
LLLiked Videos (Main YouTube)24 charsTry LL Link
LMLiked Music (YouTube Music)2 charsTry LM Link
WLWatch Later Queue2 charsTry WL Link
RDInfinite Mix / Radio13+ charsTry RD Link
OLAK5uy_Official Music Album44 charsTry OL Link

Understanding how these URLs work makes it much easier to write scripts that fetch and clean YouTube data. It definitely saved me a lot of debugging time when building the backend for YTP Length.

Note: If you want to know more about how I built this tool, check out my other post on How I Built a YouTube Playlist Tool While Learning JavaScript or read about my strategy for How I Use YouTube Playlists to Learn Fast: My 3 Secret Steps.

PreviousNext