Question 1

What is Base64 encoding?

Accepted Answer

Base64 encodes binary data into 64 printable ASCII characters (A–Z, a–z, 0–9, +, /). It's widely used in JWT tokens, email attachments (MIME), and image data URIs.

Question 2

Is Base64 a form of encryption?

Accepted Answer

No. Base64 is encoding, not encryption. Anyone can decode a Base64 string without a key. Never use it to hide sensitive data — use AES or RSA encryption instead.

Question 3

What is URL-safe Base64?

Accepted Answer

URL-safe Base64 replaces + with - and / with _ to avoid conflicts in URLs, filenames, or query parameters. JWT tokens always use URL-safe Base64.

Question 4

How much does Base64 encoding increase data size?

Accepted Answer

About 33%. Base64 converts every 3 bytes into 4 ASCII characters, so a 1 KB file becomes approximately 1.33 KB after encoding.

Question 5

Can I embed Base64-encoded images in HTML?

Accepted Answer

Yes. Use data:image/png;base64,{value} as the img src attribute. This eliminates extra HTTP requests but disables browser caching, so it's best for small icons.

Question 6

What is the = padding at the end of Base64 strings?

Accepted Answer

Base64 processes input in 3-byte blocks. When the input length isn't a multiple of 3, one or two = characters are appended to make the output length a multiple of 4.

Question 7

What is the difference between URL encoding and Base64?

Accepted Answer

URL encoding (percent-encoding) converts URL-unsafe characters to %XX format. Base64 converts binary data to text. They serve different purposes and are not interchangeable.

Question 8

What is the difference between %20 and + for spaces?

Accepted Answer

%20 follows RFC 3986 percent-encoding for URL paths. + is used in HTML form data (application/x-www-form-urlencoded). Use %20 in path segments and + in query string form data.

Question 9

Why do Korean or CJK characters become so long when URL encoded?

Accepted Answer

Korean and CJK characters typically require 3 bytes in UTF-8. Each byte encodes as %XX, so one character expands to 9 characters (e.g., %EA%B0%80).

Question 10

Can I use this tool to decode JWT tokens?

Accepted Answer

Yes. JWT tokens consist of three Base64URL-encoded parts separated by dots. Split the token at each dot and decode each part using URL-safe mode.

Question 11

Is my data sent to any server?

Accepted Answer

No. All encoding and decoding is performed in your browser using JavaScript. Nothing is transmitted to any server.

Question 12

Do I need to URL encode JSON when passing it as a query parameter?

Accepted Answer

Yes. JSON contains characters like {, }, :, ", and spaces that are special in URLs. Always URL-encode JSON strings before including them in query parameters.

Base64 & URL
인코더/디코더

Base64란?

활용 예제

URL 인코딩이란?

Base64 & URL인코더/디코더

Base64란?

활용 예제

URL 인코딩이란?

Base64 & URL
인코더/디코더