iPhones save photos as HEIC, and Windows, older software and plenty of upload forms refuse to open them. This converts them to something everything accepts, without sending your photos anywhere.
Drop in as many as you like. The .heic and .heif extensions are both handled.
JPG for anything that has to just work. PNG if you need no quality loss. WebP for the smallest file.
Check the sizes and save. Your originals are untouched.
HEIC stores the same picture in roughly half the space of a JPG, which is why Apple switched to it. The saving is real, and so is the cost: support outside the Apple world is still patchy years later, which is how a photo that looks fine on your phone becomes unopenable on a work laptop.
Expect the converted file to be larger than the original. You are trading a modern, efficient format for an older, universal one, and that trade has a size. For a photo you are emailing or uploading, that is usually the right way round.
If you would rather not deal with this again, your iPhone can be told to capture in the compatible format instead. It is in Settings, under Camera, then Formats. You lose the space saving and gain files that open everywhere.
Converting a photo is not a reason to hand it to a stranger's server. Family photographs, pictures of documents and screenshots of private conversations all end up in this queue, which is why this one converts in your own browser.
No. The work happens inside this tab, on your own machine. Open your browser's network tab while you use the tool, there is no request carrying your file.
Practical limits depend on the tool, browser and available device memory. Large files can fail even when no explicit limit is shown. Keep an original and use a smaller job if this device cannot finish it.
No, and there is no daily limit either. There is nothing to sign up for.
HEIC is a more efficient format. The same picture stored as JPG simply takes more space. That is the cost of a file everything can open.
A little, since JPG is lossy. At the default quality setting it is not visible in an ordinary photograph.
Yes, add as many as you like and they all use the same settings.
Newer iPhones save photos as HEIC, a format that keeps good quality at about half the size of a JPG. The trouble is that many websites, upload forms and Windows programs do not accept it. Converting to JPG gives you a file that opens nearly everywhere.
The decoder is built into this page and runs on your device, so the photo is not sent anywhere to be converted. You can also stop the problem at the source by choosing Most Compatible under Camera, then Formats, in your iPhone settings.
JPG is the default, at 90 percent quality. PNG loses nothing but is much larger, and WebP is smaller than JPG where the place you are sending it accepts it. The converted file is usually larger than the HEIC it came from, because HEIC is a more efficient format.
You can add many photos at once and they are converted one after another, with a count as it goes. A file that cannot be read tells you so. Use the Compress image tool afterwards if the JPG files are bigger than a form allows.