Base64 Encode/Decode

Convert data to a Base64 string, and convert a Base64 string to data

Features

Supports UTF-8 including Japanese

Accurately converts multibyte characters without garbling

Converts automatically as you type

Shows the result instantly, no button needed

Supports up to 1 million characters

Can batch-process long text and larger data

Strict Base64 validation

Shows an error for invalid strings to prevent misconversion

How to Use

Select encode/decode

Select the conversion direction with the top buttons. You can also swap input and output with the center arrow button

Enter text or Base64

Paste a string into the input field and it converts automatically. Click the sample to try it out

Copy or save the result

Copy to the clipboard with the copy button, or save as a text file with the download button

Use Cases

Embedding in data URI format

Base64-encode text such as SVG or CSS and embed it directly into HTML

Checking API response data

Quickly grasp the contents of tokens or attached data returned in Base64 during development

Generating a value for Basic authentication

Easily create an authentication string that combines a username and password

Verifying email content

Decode a MIME-encoded subject or body to investigate the cause of garbling

Basic Knowledge

What is Base64

Base64 is an encoding method that represents binary data such as images using only 64 types of characters (A–Z, a–z, 0–9, +, /), and the resulting data size is approximately 1.33 times larger than the original.

Why Convert to Base64

It is used to safely transport binary data within systems that can only handle text safely, such as email and JSON.

Data URI：A data URI is a way to embed images directly into HTML or CSS in the format "data:image/png;base64,~".
Basic Authentication：In Basic authentication, a value created by Base64 encoding "username:password" is sent, so this format conversion is necessary.

Meaning of the Trailing "="

The "=" at the end of a Base64 string is called padding, a symbol for length adjustment. One or two "=" characters are added to make the number of characters after conversion a multiple of 4.