What Is Base64 Encoding? How and When to Use It

Base64 is an encoding that represents binary data using 64 plain-text characters (A–Z, a–z, 0–9, + and /). Its whole job is to let binary data — an image, a file, raw bytes — travel safely through channels that were built for text.

Why it exists

Some systems only reliably handle plain text: email bodies, URLs, JSON fields, HTML attributes. Hand them raw binary and bytes get mangled. Base64 solves that by mapping every 3 bytes of input to 4 text characters from its safe alphabet. The trade-off is size — Base64 output is about 33% larger than the original — but it's guaranteed to survive text-only transport.

Where you'll meet it

• Data URIs — data:image/png;base64,... embeds an image directly in HTML or CSS, no separate file.
• Email attachments — MIME encodes attachments as Base64 under the hood.
• API tokens and headers — HTTP Basic Auth Base64-encodes user:password; JWT sections are Base64URL-encoded.
• Config and certificates — keys and small binaries are often stored as Base64 text.

It is not encryption

This is the one thing to get right: Base64 provides no security whatsoever. It's a reversible transformation with no key — anyone can decode it back to the original instantly. If you see credentials "hidden" as Base64, they are effectively in plain text. Use it to transport data, never to protect it. For protection you need encryption; for integrity you need hashing.

URL-safe Base64

Standard Base64 uses + and /, which have special meaning in URLs. Base64URL swaps them for - and _ (and often drops the = padding) so the result is safe in links and — as it happens — in JWTs.

Encode or decode instantly

Convert text and data to and from Base64 with the free Base64 Encoder / Decoder. It works in your browser, so nothing you paste is uploaded.

Related developer & security tools

Base64 Encoder / Decoder | JWT Decoder | Hash Generator | All free tools