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[COMPARISON] 8 min read

[COMPARISON] Base62 vs Base64: When to Use Each

Ever wondered why YouTube video IDs look like "dQw4w9WgXcQ" while JWT tokens have those weird equals signs? Let's decode when to use Base62 vs Base64.

September 13, 2025 | encoding

// THE REAL DIFFERENCE

So here's the thing about Base62 and Base64 - they're both encoding schemes, but they solve slightly different problems. I learned this the hard way when I tried to use Base64 for generating URL-friendly IDs and ended up with broken links everywhere because of those forward slashes.

Base64 uses 64 characters to encode data, while Base62 uses 62 characters. That tiny difference? It changes everything about where and how you use them.

Quick Reality Check: Neither of these is encryption. If someone sends you "secure" data that's just Base64 encoded, they don't understand security. These are encoding schemes for data transmission, not protection.

// CHARACTER SETS - BASE64

Base64: The Kitchen Sink Approach

Base64 uses these 64 characters:

A-Z (26 chars)
a-z (26 chars)
0-9 (10 chars)
+   (plus sign)
/   (forward slash)
=   (padding)

// CHARACTER SETS - BASE62

Plus it uses = for padding when the data doesn't divide evenly into 6-bit chunks. This is why JWT tokens sometimes end with one or two equals signs.

Base62: The URL-Friendly Cousin

Base62 keeps it simple with just alphanumeric characters:

A-Z (26 chars)
a-z (26 chars)
0-9 (10 chars)

// EFFICIENCY COMPARISON

No special characters. No padding. Just clean, URL-safe characters that won't break your links or confuse your users.

The Efficiency Trade-off: Base64 encodes 6 bits per character (33% overhead). Base62 encodes ~5.95 bits per character (35% overhead). For a 100-byte file, Base64 gives you 133 bytes, Base62 gives you 135 bytes. Not a huge difference, honestly.

// WHERE BASE62 WINS

YouTube Video IDs
Those 11-character video IDs like "dQw4w9WgXcQ"? Pure Base62. YouTube needs billions of unique IDs that work in URLs without encoding issues. Base62 delivers exactly that - no URL encoding needed, no confusion with path separators.

URL Shorteners
Bitly, TinyURL, and pretty much every URL shortener uses Base62. Why? Because "bit.ly/3xK9Zm2" just works. No percent-encoding, no broken links when someone copies it wrong. It works in emails, texts, everywhere.

Database IDs and API Keys
When you need short, unique identifiers that humans might type or remember, Base62 wins. I've seen it used for everything from session IDs to invite codes.

// WHERE BASE64 DOMINATES

JWT Tokens
Every JWT token you've ever seen uses Base64URL encoding (a variant that replaces + with - and / with _). The standard is built around it, libraries expect it, and it efficiently encodes the JSON payloads.

Email Attachments
SMTP was designed for 7-bit ASCII. Every attachment in every email you send gets Base64 encoded. It's been the standard since the 1990s and it's not changing.

Data URIs
Want to embed an image directly in your HTML or CSS? That's Base64. Those data:image/png;base64,iVBORw0KG... strings you see? They're everywhere in modern web development for embedding small assets.

// Embedding a tiny image in CSS with Base64
.icon {
    background: url('data:image/png;base64,iVBORw0KGgoAAAANS...');
}

// QUICK DECISION GUIDE - BASE62

✓ USE BASE62 WHEN:

  • > Building URL shorteners
  • > Generating video/content IDs
  • > Creating human-readable identifiers
  • > Making invite codes or coupon codes
  • > Needing clean URLs without encoding

// QUICK DECISION GUIDE - BASE64

✓ USE BASE64 WHEN:

  • > Working with JWT tokens
  • > Sending email attachments
  • > Embedding files in HTML/CSS
  • > Following established standards
  • > Transmitting binary data in JSON/XML

// IMPLEMENTATION REALITY

Here's something nobody talks about: Base64 has libraries everywhere. Every language, every platform. It's standardized to death. Base62? Not so much. You might end up rolling your own implementation, and different libraries might order the alphabet differently (0-9A-Za-z vs 0-9a-zA-Z).

// Base64 in JavaScript - Built-in and easy
const encoded = btoa('Hello World');
const decoded = atob(encoded);

// Base62 in JavaScript - You're on your own
const base62 = require('some-third-party-lib');
// Hope it uses the same alphabet as your backend...

// PERFORMANCE COMPARISON

Metric          | Base62        | Base64
----------------|---------------|--------------
Bits per char   | ~5.95         | 6.00
Overhead        | ~35%          | ~33%
URL-safe        | Yes           | No (needs encoding)
Padding needed  | No            | Yes
Library support | Limited       | Universal
RFC standard    | No            | Yes (RFC 4648)

// THE BOTTOM LINE

Look, both encodings have their place. Base62 shines when you need clean, human-friendly identifiers that work everywhere without special handling. Base64 wins when you need maximum efficiency, widespread support, and you're working with binary data or established standards.

The "wrong" choice usually still works - you could use Base64 for URL shorteners (just handle the special characters) or Base62 for API tokens (just accept the slightly longer strings). But why make life harder?

Pro tip: If you're building something new and asking "which encoding should I use?" - start with Base64. It's standard, it's everywhere, and Base64URL variant handles most URL-safety concerns. Only switch to Base62 if you have a specific need for purely alphanumeric output.

// REFERENCES

  • > [1] YouTube - How YouTube Works (2023)
  • > [2] JWT.io - JSON Web Token Introduction (2024)
  • > [3] IETF RFC 4648 - Base16, Base32, and Base64 Data Encodings (2006)
  • > [4] Bitly Engineering - Why We Use Base62 (2022)
  • > [5] MDN Web Docs - Data URLs (2024)

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