Image to Base64 Converter

Image to Base64 encoding converts binary image data into an ASCII text string using the Base64 encoding scheme. The result is a data URL — a string that starts with 'data:image/png;base64,' followed by the encoded image data.

This data URL can be used anywhere you'd normally reference an image file: in HTML <img> tags, CSS background-image properties, JavaScript Image objects, and even in JSON or XML payloads. The browser decodes the Base64 string back into the original image on the fly.

Base64 images are ideal for small assets where eliminating an HTTP request outweighs the size overhead. Common use cases include: tiny icons and UI sprites (under 5-10 KB), email HTML templates where external images are often blocked by mail clients, single-file HTML exports and documentation, CSS background patterns and textures, and offline-capable web applications.

As a rule of thumb, if an image is under 10 KB, the Base64 overhead (~33%) is negligible compared to the latency saved by avoiding an extra network round-trip. Above 20 KB, a separate file served over HTTP/2 is almost always more efficient.

While Base64 images save HTTP requests, they come with trade-offs. The ~33% size increase means more bytes transferred in your HTML or CSS file. Base64 strings are not cached independently — they're cached as part of the containing document. They also block rendering because the browser must download the entire HTML/CSS before it can display any Base64 images.

For optimal performance: use Base64 only for small, critical images that appear above the fold. For anything larger, use external files with proper cache headers and consider modern formats like WebP or AVIF. With HTTP/2 multiplexing, the cost of additional requests is much lower than it was with HTTP/1.1.

In HTML, embed a Base64 image as an img tag: <img src="data:image/png;base64,iVBOR..." alt="description" />. In CSS, use it as a background: background-image: url(data:image/png;base64,iVBOR...). Both approaches work in all modern browsers.

For CSS, this technique is commonly used with build tools like webpack or Vite that automatically inline small images below a configurable size threshold. You can also use Base64 SVGs in CSS, which is particularly efficient because SVGs are already text-based and compress well with gzip.