Base64 File Converter

Q: What's the maximum file size for Base64 encoding?

Browser-based encoding works up to ~50MB before memory becomes a concern. Beyond that, use a streaming encoder. The output will be ~33% larger — a 50MB file produces ~67MB of Base64 text.

Q: When should I NOT use Base64 file encoding?

Large files (>100KB), files that need caching (external URLs cache better), files you'll update frequently (data URIs require updating everywhere), and email attachments (use standard MIME attachment encoding instead).

Free online tool. All processing is client-side. No signup needed.

How to Use the Base64 File Converter

Enter your input values above
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Copy or download the output

What is a Base64 File Converter?

A Base64 File Converter encodes any file (image, PDF, audio, document) into a Base64 data URI string, or decodes a Base64 string back to its original file. Base64 file encoding is the foundation of: embedding images directly in HTML/CSS (data:image/png;base64,...), sending file attachments through text-only APIs (JSON, XML), storing binary data in text-only databases, and inlining small assets to reduce HTTP requests. This tool handles files of any type with instant preview for common formats.

How Does It Work?

Upload a file or paste a Base64 string. For encoding: the file's binary data is read, converted to Base64, and wrapped in a data URI with the correct MIME type (data:[mime];base64,[data]). For decoding: the Base64 string (with or without the data URI prefix) is parsed and the original file is reconstructed — download it with the correct filename and extension. Common file types (images, PDFs, text) show a preview.

Formula

Encode File → Base64 Data URI:\n\ndata:[<mime type>];base64,<base64-encoded-data>\n\nExample (1-pixel red PNG):\ndata:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVR42mP8/5+hHgAHggJ/PchI7wAAAABJRU5ErkJggg==\n\nSize Calculation:\nBase64 size = Ceil(original bytes × 4/3)\nPadding = 0, 1, or 2 '=' characters\nOverhead = ~33% size increase\n\nFor CSS: background-image: url(data:image/png;base64,...)\nFor HTML: <img src=\

Who Uses This Tool?

Web developers embedding small icons/images as data URIs in CSS/HTML
API developers encoding file attachments in JSON payloads
Email developers embedding inline images in HTML emails
Database designers storing small binary files as Base64 text in document stores
Anyone transferring files through text-only protocols or storage systems

Pro Tips

Data URIs eliminate HTTP requests but increase HTML/CSS size. Best for small, critical files (<10KB). Larger files should be served separately for caching
Base64 increases size by ~33% — a 30KB file becomes ~40KB. For many small files, the request elimination usually outweighs the size increase
SVG data URIs don't need Base64: use `data:image/svg+xml,` followed by URL-encoded SVG content. It's more efficient and preserves editability
For HTML email, embedded Base64 images are blocked by most email clients (Outlook, Gmail). Host images on a server and link to them via HTTPS instead

Frequently Asked Questions about Base64 File Converter

What's the maximum file size for Base64 encoding?

Browser-based encoding works up to ~50MB before memory becomes a concern. Beyond that, use a streaming encoder. The output will be ~33% larger — a 50MB file produces ~67MB of Base64 text.

When should I NOT use Base64 file encoding?

Large files (>100KB), files that need caching (external URLs cache better), files you'll update frequently (data URIs require updating everywhere), and email attachments (use standard MIME attachment encoding instead).

Free online Base64 File Converter — no signup, 100% client-side processing. All data stays in your browser.