About

This tool addresses the interoperability gap between Apple's High Efficiency Image Format and universal web standards. Unlike standard image viewers, web browsers (Chrome, Edge, Firefox) lack native decoding pipelines for the HEVC container used in HEIC files.

To solve this without compromising privacy, this application dynamically loads a WebAssembly (WASM) decoding engine directly into your browser's memory. This allows for pixel-perfect conversion to JPG, PNG, or WebP without ever sending a single byte to a remote server. The mathematical transformation involves decoding the 16-bit perceptually quantized color space of HEIC and re-mapping it to the 8-bit sRGB space required by JPEG, applying a Discrete Cosine Transform (DCT) for compression.

Formulas

The core conversion relies on the quality factor q (0 to 1). The file size S is approximately related to the entropy E of the image data:

S ≈ W × H × C × (1 − q)⁻¹

Where W and H are dimensions and C is the chrominance subsampling factor. Increasing q yields diminishing returns in quality while exponentially increasing size.

Reference Data

Parameter	HEIC (Input)	JPG (Output)	Conversion Logic
MIME Type	image/heic	image/jpeg	Container Re-encapsulation
Encoding	HEVC (H.265)	JPEG (ISO/IEC 10918)	decode → Raw Bitmap → encode
Color Channels	YCbCr / RGB	YCbCr	Color Profile Mapping
Transparency	SUPPORTED	UNSUPPORTED	Alpha channel flattened to White
Processing Location	Local CPU/GPU	Local Storage	Zero-Latency Loopback

Frequently Asked Questions

Most browsers (Chrome, Edge, Windows) do not know how to read HEIC files natively. This tool downloads a specialized "translator" (a JavaScript library) on the fly to teach your browser how to read these files. This happens once per session.

Yes. The library (heic2any) is just code logic. It is downloaded TO your computer. Once loaded, it runs entirely offline. Your photos interact with this code inside your browser, never traveling back to the source of the library.

HEIC is a heavily compressed format. Decoding it requires significant CPU math to unpack the pixel data before it can be re-compressed into JPG. This double-process (Decode -> Encode) is processor-intensive.

HEIC files from Live Photos often contain multiple images in one file. This converter will extract the primary (highest quality) still image from the container and convert that.