How JustConvertHEIC Works
Your HEIC photos are converted entirely in your browser. Here is exactly what happens under the hood.
Browser-Side Processing
JustConvertHEIC runs entirely in your web browser. When you convert a HEIC file, every step happens on your device — no file is ever sent to any server, and no external service processes your data.
Technical Implementation
The tool is built on these browser APIs and open-source libraries:
@discourse/heic
A WebAssembly build of libheif and libde265, published by Discourse as part of the jSquash codec library. Decodes HEIC/HEIF image data directly in the browser, producing raw pixel data that is then re-encoded to the target format via the Canvas API.
File API
Your browser's built-in interface for reading files you select from your device. The HEIC file is read into browser memory as a Blob — no upload, no network request.
Canvas API
Once decoded, the image is drawn onto an off-screen canvas element and re-encoded at the format and quality level you select (JPG, PNG, or WebP). This is a native browser capability — no plugins required.
JSZip
An open-source library used to package batch downloads into a single ZIP file, entirely within the browser.
What This Means for Your Privacy
- Your files are never uploaded to any server
- No third party receives or processes your photos
- We have no access to the content of your files
- No image data is logged or stored anywhere
- Files exist only in your browser's memory during processing
How to Verify
You do not have to take our word for it. Here is how to confirm:
- 1 Open your browser's developer tools (press F12, or right-click and choose Inspect)
- 2 Go to the Network tab
- 3 Use the tool to convert a HEIC file
- 4 Observe: no outbound requests contain your image data
Alternatively, disconnect from the internet after the page loads. The tool continues to work — because it requires no server.
Trade-offs and Limitations
Because processing happens on your device, performance depends on your hardware. Very large HEIC files or large batches may convert more slowly on older or low-memory devices than server-based tools. The tool automatically adjusts file size limits based on your device's detected capabilities.