What is Base64 encoding?

Base64 encoding converts binary data into 64 printable ASCII characters (A-Z, a-z, 0-9, +, /). It allows binary data to be safely transmitted over text-based protocols like HTTP, email (MIME), and JSON.

Why does Base64 increase data size by 33%?

Base64 encodes every 3 bytes of input into 4 ASCII characters. This 3:4 ratio means the output is always 33% larger than the input. Padding characters (=) may add a few more bytes when the input length is not a multiple of 3.

What is the difference between standard and URL-safe Base64?

Standard Base64 uses + and / characters that have special meaning in URLs. URL-safe Base64 replaces + with - and / with _ so the encoded string can be safely used in URLs, filenames, and query parameters without percent-encoding. JWT tokens always use URL-safe Base64.

Is Base64 encryption?

No. Base64 is encoding, not encryption. It is easily reversible without any key. Never rely on Base64 to protect sensitive data — use AES, RSA, or other proper encryption algorithms for that purpose.

How do I encode an image to Base64 for use in HTML?

Use the file drag-and-drop or file picker on this page to select your image. The tool will produce a Base64 string you can embed in HTML as: . Best used for small icons to avoid browser caching issues.

How does file encoding work in the browser?

When you drop or select a file, the browser reads it as a data URL (data:type;base64,...) using the FileReader API. The tool extracts the Base64 portion after the comma. The file never leaves your device.

What are common use cases for Base64 encoding?

Common uses include: embedding images in HTML/CSS as data URIs, JWT token payloads (URL-safe), HTTP Basic Auth credentials, email attachments (MIME), API authentication headers, inline fonts in CSS, and transmitting binary data in JSON or XML.

Is my data sent to a server when I use this tool?

No. All encoding is performed entirely in your browser using the Web Crypto API and TextEncoder. No data, files, or results are transmitted to any server.

Base64
Encoder

텍스트·파일을 Base64로 인코딩

인코딩 방식:

Standard

URL-safe

텍스트를 입력하거나 파일을 드래그하세요

입력 (텍스트) 0자

출력 (Base64) 복사

파일을 여기에 드래그하거나 클릭하세요

Base64Encoder

Base64
Encoder