Guides · 2026-03-11
What Is Base64 Encoding? A Plain-English Guide
Understand what Base64 is, when to use it, and how to encode or decode text and files for free in your browser.
You've probably seen long strings like aGVsbG8gd29ybGQ= in code, emails, or data files. That's Base64 — and it's simpler than it looks. Here's what it is and when you'd use it.
The core idea
Base64 converts binary data (or text) into a set of 64 safe, printable characters: A–Z, a–z, 0–9, plus + and /. It's not encryption — anyone can decode it. Its job is to let data travel safely through systems that only handle plain text.
Why it exists
Many older protocols — email being the classic example — were designed for text, not raw bytes. Sending an image or any binary file directly could corrupt it. Base64 repackages those bytes as text so they survive the trip, then get decoded back on the other end.
Where you'll see it
- Email attachments (MIME) are Base64-encoded behind the scenes.
- Data URLs embed small images directly in HTML/CSS as
data:image/png;base64,.... - API tokens and config often store binary values as Base64 text.
One catch: it's bigger, not smaller
Base64 makes data about 33% larger, because it uses 4 characters to represent every 3 bytes. It's for compatibility, not compression — don't use it to shrink files.
Encode or decode for free
Use the free Base64 tool to convert text in both directions, with full UTF-8 support. Like all our tools, it runs in your browser, so nothing you paste is uploaded.