Question 1

How does file-to-Base64 encoding work?

Accepted Answer

Each byte of your file is read into an ArrayBuffer, then converted to a Base64 string using btoa (binary-to-ASCII). The result can be output as raw Base64, a data: URL (with MIME type prefix), URL-safe Base64 (with -_ replacing +/), or line-wrapped at 76 characters per line (RFC 2045).

Question 2

What's a data URL?

Accepted Answer

A data URL embeds the entire file inline as `data:;base64,`. You can paste it directly into , , or CSS url() without a separate request. Useful for inline images, embedded fonts, and self-contained HTML.

Question 3

What extra features does this tool have?

Accepted Answer

10 extras: (1) Drag-drop file. (2) Batch encode multiple files. (3) Size warning for files > 2MB. (4) URL-safe Base64 output (-_ instead of +/). (5) Line-wrapped output at 76 chars (RFC 2045). (6) Stats (input size, output size, overhead %). (7) Preview first 500 chars. (8) Copy as data URL. (9) Copy as raw Base64. (10) History (localStorage — last 10 encodings).

Question 4

Is my file uploaded anywhere?

Accepted Answer

No. All encoding runs in your browser using FileReader / ArrayBuffer. Your file never leaves your device.

Question 5

Why is the Base64 output ~33% larger than the original?

Accepted Answer

Base64 encodes every 3 bytes into 4 ASCII characters (6 bits each). This 4/3 ratio means a 3 KB file becomes 4 KB of Base64 text. The stats panel shows the exact overhead percentage so you can plan for it.

Base64 File Encoder

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