Base64 Encode/Decode

What is Base64

Base64 is an encoding scheme that converts binary data into plain ASCII text. It uses 64 printable characters (A-Z, a-z, 0-9, +, /) to represent arbitrary byte sequences, and is widely used to transmit binary content over text-based protocols.

How It Works

Every 3 bytes of binary data → 4 Base64 characters, resulting in roughly 33% size increase. When the byte count is not a multiple of 3, = padding is added.

Base64 vs Base64URL

	Standard Base64	Base64URL
Charset difference	+ / =	- _ (no =)
Use cases	Email, Data URLs	JWT, URL params, filenames

Base64 is encoding, not encryption — anyone can decode it. Never use it to protect sensitive data.

Common Use Cases

• Embedding small images in HTML/CSS as Data URLs to reduce HTTP requests
• Email attachment transport (MIME encoding)
• Storing binary data in text-only formats like JSON or XML
• Encoding JWT token headers and payloads

How to Use

1. Paste the raw text you want to encode, or a Base64 string you want to decode, into the input area
2. Select the operation mode (encode/decode) and variant (standard Base64 or Base64URL)
3. The result is generated in real time — click the copy button to use it

FAQ

Why do I get garbled text when decoding Chinese characters?

Make sure encoding and decoding use the same character set. This tool defaults to UTF-8. If the original data was encoded with GBK or another charset, convert it to UTF-8 first.

Can I put a Base64 string directly in a URL?

No. Standard Base64 contains +, /, and =, which have special meanings in URLs. Use the Base64URL variant instead, or URL-encode the result.

Why is the encoded output larger than the original?

Base64 represents every 3 bytes with 4 characters — a fixed ~33% overhead. For large files, prefer binary upload over Base64 encoding.