Base64 String Encoder & Decoder
Encode and decode Base64 strings instantly with this free online converter. Supports standard and URL-safe Base64. No sign-up required, runs entirely in your browser.
What is Base64 Encoding?
Base64 is a binary-to-text encoding scheme that converts binary data into a printable ASCII string format. It represents binary data using 64 characters (A-Z, a-z, 0-9, +, /) plus '=' for padding. Base64 encoding is widely used in web development to embed binary content — such as images, fonts, or file attachments — inside text-based formats like JSON, HTML, CSS, and email (MIME). The encoding follows the specification defined in RFC 4648. Because each group of 3 bytes becomes 4 Base64 characters, encoded output is roughly 33% larger than the original data.
How to Use This Free Online Base64 Encoder & Decoder
- Paste or type the text you want to encode or decode into the input field.
- Select the mode: Encode (text → Base64) or Decode (Base64 → text).
- The result appears instantly in the output field — no button click needed.
- Click the Copy button to copy the result to your clipboard.
Common Use Cases for Base64 Encoding
- Embedding images in HTML or CSS — Convert small images to Base64 data URIs to reduce HTTP requests and inline them directly in your markup or stylesheets.
- Encoding data in JSON APIs — Safely transmit binary payloads (like file content or cryptographic signatures) inside JSON strings without escaping issues.
- Email attachments (MIME) — MIME-encoded emails use Base64 to embed binary attachments inside the text-based email format.
- HTTP Basic Authentication headers — The Authorization header encodes the username:password pair in Base64 before sending it to the server.
- Storing binary data in text-only databases or configs — When a storage system only accepts text, Base64 lets you safely persist binary blobs without corruption.
FAQ
Is Base64 encoding the same as encryption?
No. Base64 is an encoding scheme, not encryption. It does not provide any security — anyone can decode a Base64 string back to the original data. For secure data protection, use AES or another encryption algorithm.
Why does Base64 increase the data size by about 33%?
Base64 encodes every 3 bytes of input into 4 ASCII characters. This 4/3 ratio means the output is approximately 33% larger than the input. Padding characters ('=') may add a few extra bytes.
What is URL-safe Base64?
Standard Base64 uses '+' and '/' characters, which have special meaning in URLs. URL-safe Base64 (also called Base64url, defined in RFC 4648 §5) replaces '+' with '-' and '/' with '_', and typically omits padding. This makes the encoded string safe to use in URLs and filenames.
Is this tool free and private?
Yes. This tool is completely free, requires no sign-up, and runs entirely in your browser using JavaScript. No data is sent to any server — your input stays on your device.