Base64 Image & Data URI Converter
Convert images to Data URIs (data:image/png;base64,...), HTML <img> tags, and CSS background-image snippets.
Drag & Drop image to convert to Base64 Data URI
Supports PNG, JPG, WebP, SVG, GIF up to 20MB.
How do I use Base64 Image & Data URI Converter?
Upload an image to encode into a `data:image/...;base64,` URI, or paste a Base64 string / click "Load Sample Data" to decode.
Inspect the live image preview, pixel dimensions, MIME type, and Base64 byte overhead.
Copy the raw Base64 string, HTML `<img src="...">` tag, or CSS `background-image: url(...)` snippet.
What features does Base64 Image & Data URI Converter offer?
100% client-side Data URI conversion using FileReader API
Generates Data URI string, raw Base64, HTML <img> tag, and CSS background snippet
Live image dimension (width/height) & file size inspection
Zero server uploads or privacy tracking — 100% local processing
RFC 2397 Data URI Scheme & Base64 Size Inflation Analysis
Base64 encodes every 3 binary bytes ($24\text{ bits}$) into 4 ASCII characters ($4 \times 6\text{ bits}$), increasing payload size by exactly $33.33\%$ ($\lceil n / 3 \rceil \times 4$).
| Original Image Size | Base64 Encoded String Size | Gzip / Brotli Compressed Size | Performance Recommendation |
|---|---|---|---|
| < 2 KB (Small Icon / Spinner) | ~2.67 KB (+33%) | ~1.9 KB | Ideal for inline Data URI (eliminates HTTP request) |
| 10 KB (UI Graphic) | ~13.3 KB (+33%) | ~10.4 KB | Borderline — prefer external `.webp` or SVG sprite |
| 100 KB (Hero Photo) | ~133.3 KB (+33%) | ~102 KB | Anti-pattern — blocks HTML/CSS critical rendering path |
| 1 MB (High-Res Image) | ~1.33 MB (+33%) | ~1.02 MB | Severe LCP penalty; cannot be cached independently |
Frequently Asked Questions about Base64 Image & Data URI Converter
Why does encoding an image to Base64 increase its byte size by 33%?
Base64 maps 6 bits of binary data (`2^6 = 64` printable ASCII characters) into an 8-bit ASCII byte (`1 byte` in UTF-8 HTML/CSS). Consequently, every 3 bytes of raw image data require 4 ASCII characters (`4 / 3 = 1.3333`).
When does inlining Base64 images hurt Google Core Web Vitals (FCP and LCP)?
Inlining images larger than `4 KB` inside CSS files blocks the browser's render-blocking stylesheet download and prevents the image from being cached separately from your HTML/JS bundle.
How can you identify the image MIME type from the first few characters of a raw Base64 string?
Binary file magic bytes produce deterministic Base64 prefixes: `/9j/` is always **JPEG** (`FF D8 FF`), `iVBORw0KGgo` is **PNG** (`89 50 4E 47`), `R0lGOD` is **GIF** (`GIF8`), `UklGR` is **WebP** (`RIFF`), and `PHN2Zy` is **SVG** (`<svg`).
Should SVG icons be Base64-encoded inside CSS `url()` declarations?
For SVG icons inside CSS, URL-encoding minimal reserved characters (`data:image/svg+xml;utf8,<svg ...>`) is actually 20–25% smaller and compresses better under Brotli than `data:image/svg+xml;base64,...`.
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