Are Online Google Takeout Metadata Fixers Safe?
Uploading your whole photo library to a website to fix its dates is a real privacy decision. Here is what to weigh, and the offline alternative.
Some of them work. That is not the same as being a good idea.
To fix your dates, a website needs your photos and your .json files. That means uploading your entire personal library, every family photo and every document you ever snapped, to a server you know nothing about. You are trusting a stranger's storage, their retention policy, their security, and their business model. Most of these sites are small operations with no published policy at all. Even when the intent is honest, the upload itself is the risk. There is also the practical problem: a 300 GB export is not something you upload twice.
The work does not need a server. Reading a .json file and writing an EXIF tag is something your own computer does easily.
This app runs entirely on your machine. Your photos never leave it, there is no account, no sign-in and no upload, and it works with your network off. That is not a marketing line, it is the design: the only thing it ever touches the internet for is the optional place-name lookup, which you can leave switched off. The first 500 photos are free, and you can verify the results yourself before going further.