Base64 Encoder/Decoder

What Base64 Is (and What It Is Not)

Base64 is a way to represent binary data as plain text. It is commonly used when you need to send or store bytes in systems designed for text, such as JSON payloads, HTML attributes, CSS, email bodies, or log streams. Base64 is not a file type and it is not a compression method. Most importantly, it is not encryption. If something must be secret, it needs real encryption or a secure transport mechanism, not Base64.

Why Base64 Increases Size

Base64 works by mapping groups of 3 bytes into 4 characters. Because 4 is larger than 3, the encoded output is larger than the original data. The typical overhead is about one third, plus optional padding characters (=) and optional line breaks (used in some email and legacy systems). This tool shows size changes so you can quickly see the impact before embedding Base64 in an API or a config.

Text Base64 vs File Base64

When you encode text, you first turn characters into bytes using an encoding such as UTF-8. The Base64 output depends on those bytes. If you decode Base64 that originally came from a file (like PNG or PDF) and try to display it as text, it may look like “garbled” characters because the bytes are not meant to be interpreted as text. In that case, decode the bytes and download the file instead.

URL-Safe Base64 (Base64url)

Standard Base64 uses two characters (+ and /) that can cause problems in URLs and cookies unless escaped. URL-safe Base64 replaces them with - and _. Many systems also omit padding (=) for convenience. This tool converts in both directions and can add or remove padding depending on what your target system expects.

Data URIs and When to Use Them

A Data URI embeds data directly into a URL-like string, for example:

data:image/png;base64,iVBORw0KGgo...

This is useful for small assets such as tiny icons, small CSS images, or quick prototypes where you want a single file without external requests. For large images or fonts, Data URIs can bloat HTML/CSS and hurt caching. The Data URI tab helps you create and parse these safely, showing the MIME type and payload size.

Padding, Line Breaks, and Compatibility

Some libraries are strict and require Base64 length to be a multiple of 4 (with padding). Others accept missing padding and ignore whitespace. If you encounter “InvalidCharacterError” or similar decode errors, the issue is often missing padding or URL-safe characters being decoded by a standard decoder. This tool can normalize URL-safe alphabets and add padding so you can get a clean decode across environments.

Practical Use Cases

• API debugging: decode Base64 fields from API responses to see what they contain.
• File transfer: embed a small binary payload in JSON for a controlled environment.
• JWT segments: JWT uses Base64url (URL-safe) without padding for header and payload segments.
• Data URIs: inline small images or SVG/PNG snippets for quick prototypes.
• Email tooling: some MIME systems wrap Base64 at 76 characters per line.

Privacy Notes

Base64 is often used to wrap sensitive content like tokens, keys, or personal data. This tool runs locally in your browser and does not upload your content. Still, treat Base64 as readable data: if you paste it into public logs or share screenshots, anyone can decode it. Redact secrets before sharing.