Free Online Image to Base64 Converter
Embedding small images in HTML and CSS eliminates HTTP requests. Our free converter turns any image into a Base64 data URI for img src or CSS background-image, or outputs the raw Base64 string without the data URI prefix for use in APIs and backend code. File size and Base64 string length are displayed alongside a preview of the uploaded image. Processing is entirely local — your images never leave your device.
Data URI vs Raw Base64
A Data URI includes the MIME type prefix (e.g., data:image/png;base64,...) and can be used directly in HTML img tags and CSS. Raw Base64 is just the encoded string without the prefix — useful when passing image data to APIs, storing in databases, or embedding in JSON payloads.
When to Use Base64
Small icons under 2-3KB, CSS backgrounds, email templates. Avoid for images over 5-10KB — the 33% size increase outweighs the saved request.
Frequently Asked Questions
How much does Base64 increase size?
Approximately 33%. Every 3 bytes become 4 Base64 characters. The tool shows both the original file size and the Base64 string length so you can see the overhead.
What is the difference between Data URI and raw Base64?
Data URI includes the data:image/...;base64, prefix needed by browsers. Raw Base64 is just the encoded data, which is what APIs and databases typically expect.
Can I use Base64 in CSS?
Yes. Use url(data:image/png;base64,...) in background-image. Copy the Data URI output directly.
Which image format works best?
SVG for icons, PNG for transparency, JPEG for thumbnails. The tool accepts all common image formats.