I built a HEIC to PDF converter that never uploads your file. Here's what that cost.

Nadia, the creator of HEICtoPDF, built the service to convert iPhone HEIC photos into PDFs without ever uploading the file. This was the starting point of her project, an attempt to address the issue that many upload forms do not accept HEIC files. The user base of this tool is primarily made up of people who need to submit photos of important documents like passports, driver's licences, and utility bills.

Since uploading these files is a security risk, doing the conversion locally is the only way to ensure the user's privacy.

The main cost of this constraint is a file size ceiling of 10MB per input file. This is due to the limitations of running the conversion process in a browser tab, which uses the user's device memory. With this limitation in place, the tool is unable to handle larger files or merge multiple files into one PDF. Additionally, the conversion process also applies a lossy output, converting each photo to JPEG quality 0.85 and fitting it to an A4 page. This means that the output is not a bit-for-bit copy of the original file.

Performance is another aspect that cannot be fixed from the client-side. The conversion process depends on the capabilities of the user's device, and there is no way to control the speed of the conversion. The tool also does not provide features such as lossless compression, OCR, or text extraction, as these would further expand the tool's scope beyond its intended purpose.

Despite these constraints, Nadia has found that the decision to exclude certain features has actually paid off. For instance, merging multiple photos into one PDF is a frequent use case for users, and this can be achieved directly within the tool. This eliminates the need for users to upload their files to external servers and risk compromising their privacy. Ultimately, Nadia believes that the constraints she has put in place are worth it, as they help to make the tool more secure, efficient, and user-friendly.