Base64 Encoder/Decoder — Online Base64 Tool
Encode and decode Base64 strings online. Convert text to Base64 or decode Base64 to plain text and binary data.
💻 Developer Tools
✅ Free
By SwiftCalcTools Editorial Team · Formula verified
Loading Base64 Encoder/Decoder…
Preparing your calculator
How to Use Base64 Encoder/Decoder
- 1Enter the required values in the input fields above.
- 2Click the Calculate button or results update instantly as you type.
- 3View your results in the output panel below the inputs.
- 4Adjust any values to recalculate instantly.
Frequently Asked Questions
Base64 encodes binary data as ASCII text using 64 printable characters (A-Z, a-z, 0-9, +, /). It is NOT encryption — anyone can decode it. It increases size by ~33% (3 bytes → 4 characters). Used in email attachments (MIME), data URIs in HTML/CSS, JSON payloads, and HTTP Basic Auth headers.
Use Base64 when: embedding binary data (images, files) in text-only formats (JSON, XML, HTML). Storing binary data in databases that only support text. Transmitting binary in HTTP headers or URLs (use URL-safe Base64 for URLs). Encoding credentials in HTTP Basic Auth (NOT for security — combine with HTTPS).
Standard Base64 uses + and / which have special meaning in URLs. URL-safe Base64 replaces + with - and / with _ and omits padding (=). Example: standard btoa() output may contain +/= which must be percent-encoded in URLs. Many APIs (JWTs, Firebase) use URL-safe Base64 (also called Base64url).
Base64 expands data by 33–36%: every 3 bytes become 4 ASCII characters. With line breaks (MIME standard, 76 chars/line), overhead is ~37%. Example: 1 MB binary file → ~1.37 MB Base64. When transmitting over HTTP with gzip compression, Base64 compresses poorly because its character set is not repetitive.