What is Base64 Encoder / Decoder?
Base64 Encoder / Decoder converts plain text into Base64-encoded strings and back again. Base64 is a binary-to-text encoding scheme that represents binary data using 64 ASCII characters (A–Z, a–z, 0–9, +, /), making it safe for transmission over text-based protocols like HTTP, SMTP, and JSON. This tool handles encoding and decoding instantly with full Unicode and UTF-8 support.
When to use it?
Use the Base64 tool when you need to embed binary data — such as images, fonts, or certificates — directly into HTML, CSS, or JSON files. It’s essential when working with APIs that require Base64-encoded payloads, decoding authentication tokens, or preparing MIME email attachments. It’s also useful for debugging encoded values you encounter in logs, URLs, cookies, and configuration files.
Typical tasks developers solve with it:
- Embed small images as data URIs directly in HTML and CSS
- Encode API credentials for HTTP Basic Authentication headers
- Decode JWT token segments for rapid visual inspection
- Convert binary certificate data (PEM) into a text-safe format
Step-by-step: how Base64 encoding works
Base64 converts every 3 bytes of input into 4 ASCII characters. First, the bytes are concatenated into a 24-bit sequence. That sequence is split into four 6-bit groups, and each group maps to one of the 64 characters in the Base64 alphabet. If the input length isn’t divisible by 3, padding characters (=) are appended. For example, the text Hi (2 bytes) yields SGk= — the trailing = signals one byte of padding.
Base64 vs URL encoding vs Hex encoding
| Feature | Base64 | URL Encoding | Hex |
|---|---|---|---|
| Size overhead | ~33% | Varies (up to 3×) | 100% |
| URL-safe | No (use URL-safe variant) | Yes | Yes |
| Human readable | No | Partially | No |
| Best for | Binary data in text | Query parameters | Hashes, debugging |
Choose Base64 when embedding binary content like images or certificates in JSON, HTML, or email. Use URL encoding for query-string parameters and form data. Use hexadecimal for hash outputs, color codes, and low-level debugging where byte-level inspection matters.
Base64 in different programming languages
In JavaScript, use btoa() / atob() for Latin-1 text, or Buffer.from(text).toString('base64') in Node.js for full UTF-8 support. Python ships the base64 module with b64encode() and b64decode(). Go provides encoding/base64 with StdEncoding and URLEncoding variants. Java offers java.util.Base64 with getEncoder() and getDecoder(). Each language handles UTF-8 input slightly differently, so always confirm the character encoding matches the producer’s expectations before decoding.