Photos for email and forms: format, size and the location inside the file

Which format for what

Choose the format for the receiver, not for quality. Every device and program opens a JPG, so it is the safe choice for photos you send by email or message or attach to a form.

PNG is better for screenshots, logos and graphics with sharp edges or transparent areas. When such an image is converted to JPG, the transparent areas have to be filled with something, because JPG has no transparency — the tool fills them with white, and you can pick black instead.

HEIC is the format an iPhone takes photos in. Why it does not open on Windows, and which phone setting avoids it, is explained on the HEIC to JPG converter page; here it is enough to know that it should be converted before sending.

For a document with several pages — both sides of an ID card, a contract, a receipt — one PDF is handier than five separate images: the receiver gets one file, and the pages stay in the order you set.

Size: count pixels, not megabytes

A 12-megapixel photo, say 4032 × 3024 pixels, has more detail than a form or an email will ever show. When the size has to come down, the most reliable way is to set the longest side: the other side shrinks in the same proportion, so the image is not distorted.

A longest side of 2048 pixels gives 2048 × 1536 and 74% fewer pixels, 1600 gives 1600 × 1200 and 84% fewer, and 1280 gives 1280 × 960 and 90% fewer. The file size in megabytes falls along with the pixel count, but by exactly how much depends on the content of the photo and the quality, which is why the table is in pixels.

The JPG quality slider in the tools is set to 85% by default, a reasonable starting point for photos. If a photo is going to be printed, raise it to 92–100% and keep the full pixel count.

If there is text in the image, open the result after resizing and check that the small print is still readable. That is the only check that really tells you the photo is big enough.

Several photos in one PDF

The PDF tool puts each photo on its own A4 page (210 × 297 mm), with a 10 mm margin unless you change it. The page order is the order in the list, so arrange it before you create the file.

The page orientation follows each photo. A landscape 4032 × 3024 photo gets a landscape page and covers 253.3 × 190 mm of it; on a portrait page the same photo would be 190 × 142.5 mm — 56% of that area, with empty space above and below.

JPG photos go into the PDF without being compressed again, so they lose no quality. The one exception is a JPG carrying an EXIF rotation flag — often a portrait photo from a phone: a PDF has no such flag, so the tool first redraws that photo upright. HEIC and WebP are converted to JPG first, because a PDF cannot hold them directly.

What else travels with a photo

Besides pixels, a phone writes data into the photo: the date and time it was taken, the device model and, if the camera is allowed to use location, the coordinates of where the photo was taken. That data travels with the file, and anyone who receives it can read it.

When you convert an image with these tools — HEIC to JPG, PNG to JPG, JPG to PNG, or WebP to JPG and PNG — the new file is created by drawing the pixels again. Data from the original file, location included, is not copied into it. The orientation is applied to the pixels themselves along the way, so an upright photo stays upright.

A PDF is different. A JPG photo that needs no rotation goes into the PDF byte for byte, exactly as it is — with all of its data, location included if the phone recorded it. HEIC, WebP and a JPG that has to be rotated are drawn again first, so their data does not end up in the PDF.

If you do not want the location to travel with a document, convert the photo from JPG to PNG first and only then create the PDF — the file will be larger, because PNG is a lossless format — or turn off location for the camera in your phone's settings before taking the photo.

Where the photos are processed

All of these tools run in your browser. The photos you pick are not sent anywhere: the page has nowhere to receive them. To be precise, the page still loads ads and visitor measurement like the rest of the site — the claim is about the contents of your files, which never leave the browser.

You can process up to 10 files at once. A single file can be up to 60 MB on a computer and up to 25 MB on a phone, because a phone browser runs out of memory more easily; the total allowed is 200 MB, with at most 50 megapixels per image.

When you close or refresh the page, the selected images and results are gone from the browser's memory. Nothing is kept for next time.